Silly Home Security


Ask anybody who’s made money robbing houses, and they’ll tell you straight up: you can get away with a lot of loot in the 10 minutes before the cops come.

But the crooks won’t find their way out of the foyer if you hit ’em with the FogSHIELD—an add-on to your home security system that releases a blinding blanket of fog to stop thieves in their tracks. When an intruder triggers the alarm, water mixes in the FogSHIELD’s glycol canister to generate enough dry, non-toxic fog to cover 2,000 square feet in less than 15 seconds. It dissipates 45 minutes later, leaving your furniture unsullied and your electronics intact.

The website appears not to be a joke.

EDITED TO ADD (6/23): In the comments, a lot of people have taken me to task for calling this security silly. I stand by my statement: not because it’s not effective, but because it’s not a good trade-off. I can certainly imagine scenarios where filling your house with vision-impairing fog is just the thing to foil a would-be burglar, but it seems awfully specific a countermeasure to me.

Home security—like all security, really—is a combination of protection, detection, and response. Locks and bars are the protection system, and the alarm is the detection/response system. Fogshield is a protection system: after the locks and bars have failed, Fogshield 1) makes it harder for the burglar to navagate around the house, and 2) potentially delays him until the response system (police or whomever) arrives.

But it has problems as a protection system. For one, false alarms are way worse than before. It’s one thing to have a loud bell annoy the neighbors until you turn it off, it’s another to fill your house with fog in less than 15 seconds (plus the cost to replace the canister).

This whole thing feels real “movie-plot threat” to me: great special effect in a movie, but not really a good security trade-off for home use. An alarm system is going to make an average burglar go to the house next door instead, and a dedicated burglar isn’t going to be deterred by this.

Posted on June 21, 2007 at 6:55 AM115 Comments


merkelcellcancer June 21, 2007 7:12 AM

This beats the story about homeland security being hit with 800 intrusions, several virus attacks from within and without and hacking tools found in several computers in the department.

Yes, in a fog today.

Mike Schiraldi June 21, 2007 7:22 AM

I don’t want to look dumb here, but what are some of the reasons this is such a terrible idea?

Yes, it could be very annoying if accidentally triggered by a friend or family member, and i don’t really see the point of releasing it in the garage, but it’s damn funny to picture a burglar groping around trying to find jewelry or electronics by touch.

I’d like to hear a more fleshed-out criticism.

Guan Yang June 21, 2007 7:29 AM

A system like this was installed in my old office. A coworker once activated it by mistake, and he tells me that it actually works: He couldn’t get around the room (around 80 square meters) without bumping into furniture because you can’t see anything. I later saw the surveillance video: After a couple of seconds the screen is just gray from the fog.

Simon June 21, 2007 7:34 AM

Agreed. It may not be a foolproof solution, but I think it would have a good shock effect. Of-course, if the idea becomes commonplace, then the value of this tool quickly shrinks away as burglars recognize it to be just a standard home security solution. The other negative is that in most cases it would target only a specific room, somewhat limiting the security to only one entry point out of (possibly) many.


J. Bono June 21, 2007 7:35 AM

I agree that he garage is a pretty silly place for an example. The thief could just hop into a car and back out, cars are easy to find like that because they’re, well, big.

The real value for this, I think would be in the home or office setting where the startling effect the smoke and alarm have might cause them not to make that last step through the window.

The criticism I have of the system is, if the thief gets inside and can’t find their way out, you have a scared bad guy and the police can’t see where he is. As a paramedic, I can think of several scenarios that would be disastrous, especially with the amount of time it takes to ventilate the area. The obstruction caused by the smoke would make it difficult at best to extricate an person who was, say, injured by the trapped and obscured thief.

Hullu June 21, 2007 7:36 AM

I also wonder after looking at the site and googling about glycol fog whether Mr. Schneier for once jumped into a hasty conclusion? On the first glance (and 10 minutes spent investigating) it looks like a pretty smart device to me.

Although I don’t see how the fog wouldn’t dissipate from an open garage fast, but indoors…

Anonymous Coward June 21, 2007 7:37 AM

The problem is real (time window before alarm triggering and police arrives). I used to live in area where a lot of houses were robbed despite alarms.

The solution provided is not that dumb. And if it fails, it does it “gracefully”. (just some smoke for a a short moment in your house)

It’s far from being the worst thing I have seen lately.. Why is it categorised as silly?

Rich June 21, 2007 7:57 AM

If you could get a door or window open, would this provide a “smoke screen” to hide your escape?

How effective would it be to crawl on the floor, as one is supposed to do in a fire? (Does a glycol fog rise or sink?)

Mark June 21, 2007 8:02 AM

A similar system has been used successfully in shops and warehouses to counter ‘ram-raiders’ who would use a vehicle to break in, steal goods, then flee before police or security guards arrive. This proved to be the most successful way of minimising such losses.

My concern would be making sure that the fire brigade are aware. I could imagine it scaring away a burglar, but a neighbour then reports the smoke …

Mike Schiraldi June 21, 2007 8:04 AM

@Rich: Crawling along the floor might help, but it’s hard to find stuff to steal that way — or to carry anything you do find.

Cliv Robinson June 21, 2007 8:06 AM

In the U.K. a similar system is known as a “Smoke Shield” and has proved fairly effective in use.

However where it proves very very effective is where it is also used with flashing strobe lights and high intensity sound alarms.

The resulting disorientation caused to people has been known to make them vomit.

So yes it does work very very well when used properly.

Ken June 21, 2007 8:15 AM

A concern I have heard centers around the fog being accidentally released in the case of a real emergency, such as a fire.

Philippe June 21, 2007 8:18 AM

The biggest drawback is that you need one for every room in the house you want to protect. The livingroom , the kitchen perhaps if you hide away your jewelry in your freezer, your bedroom…

Sez Me June 21, 2007 8:20 AM

I could just see a burglar trigger it, break his nose, then sue the home owners.

As Ken said, if it were triggered during a real emergency, it would be a true disaster. I could imagine fire fighters killed because they were blind during a fire, not to mention families.

Not the best security option.

Konrads Smelkovs June 21, 2007 8:32 AM

I can’t see anything stupid about it as well. The original link raises a valid point about pets, which lead to conclusion that this device is best used to protect warehouses, stores and other industrial buildings.
The other issue was that it could trip fire-detectors. For one, this system could be actually integrated into the monitoring system and “suppress” smoke sensitive fire-detectors and rely on thermal ones for duration of the smoke shield (in case the intruder decided to set it on fire).
Furthermore, to prevent neighbors from alerting the fire dept. smoke could be in some unusual color – dark green afaict isn’t a product of common chemicals burning.
I can imagine an attack against this system – throwing a rock in a window and watching the fog start (or not start if there is no such system installed); possible mitigation would be tempered glass or other window protection + motion detectors. If a window is smashed but no motion, then do not fire the smog.

As a footnote, if the system becomes more or less common, I am sure some chemist would synthesize a reagent that, when sprayed dissipates the fog; a prepared thief would smash the window, throw in the dissipater and carry on.

Overall a nice addition to physical security arsenal, albeit one that requires more careful planning.

JeffM June 21, 2007 8:33 AM

Cliv said, “The resulting disorientation caused to people has been known to make them vomit. So yes it does work very very well when used properly.”

I personally do not consider having people I don’t know and don’t want in my house in the first place vomiting in my house to be an effective security solution. And I’d fear someone setting it off accidentally. And slip covers only help so much.

Anyway, I would like to see why this is just silly. Well, it is silly to be sure. More of why it might be a bad idea.

Anyone else thinking Logan’s run here for parties?

Dave H. June 21, 2007 8:42 AM

Man, it’d get on your nerves if it tripped while the house was on fire and you were trying to get your kids out. Trade-offs…

A Swede June 21, 2007 8:43 AM

A couple of weeks ago, there was an attempted robbery at a money depot here nearby. Early dawn, several people with heavy weapons smashed through fences and doors with a large wheel loader. They aborted the attempt and fled after a few seconds when a fog generator turned the building solid inside. 🙂

QED, it works, but I’ve never seen it sold to home owners before.

BLP June 21, 2007 8:46 AM

Glycol fog generally doesn’t look like smoke from a fire– it does set off fire alarms, especially the beam detector type. However, it being glycol and water, it will leave a film on everything. I imagine it wouldn’t leave a film the first time you fire it off, but if you had a few false triggers, you might find your hardwood floors a little slippy.

On the safety front, various groups believe various things, but in “normal entertainment concentrations”, it’s considered safe. Not sure how these devices work, however. More reading here:

NotThugTheTheif June 21, 2007 8:47 AM

If you are up agist thug the theif this might work. —MIGHT Because if the windows are open in a house the fog is not going to linger for 40 mins…. And that 10 min response time is often longer. Better doors and windows would work better.

Agaist a real theif, this will do almost nothing. You have more than your eyes and they probably already have a good idea of where to go.

Jurgen June 21, 2007 8:54 AM

So the cops show up and the intruder is still in the house but they can’t arrest him because they can’t see through all the fog. Also I have a problem with armed officers running around in a house completely blind. Especially when I’m in it.

I don’t know which risks are worth worrying about and which are unreasonable. So it might still be a good idea.

Sean Cleary June 21, 2007 9:03 AM

Cool! if just water, then maybe a way to cool off in the summer time? So just turn off the Glycol canister and trigger! Instant party?
And how does getting your electronics slightly wet fail to harm? Or worse glycol covered? Computers have mother boards that could be bothered by such.

Joe Patterson June 21, 2007 9:06 AM

I recall seeing this first on a TV show called “To catch a thief”. The idiotic thing about the situation they used it in was that they combined it with a comprehensive CCTV surveillance system. So once the fog generator went off, there was absolutely no value from the CCTV, no way to identify the intruder, know what he was able to do in the fog, nothing.

Alan Porter June 21, 2007 9:11 AM

The real question is whether you are trying to: (1) deter a thief (2) make a thief leave the house quickly (3) trap a scared (and possibly armed) thief in your home.

I’ll take curtain #1, please.

Ian Mason June 21, 2007 9:12 AM

I’ve had the unfortunate experience of being caught in a small fire in my own home. Some points:-

A small oil fire in my kitchen – detected as it ignited – filled the whole house with impenetrable smoke in 30 seconds or so. Isolating the fire (by shutting the kitchen door) and venting the corridors (by opening outside doors) still left the smoke levels in the rest of the house high enough that I could not see to evacuate the cats. The relevent point being that smoke or fog from a single point, generated in sufficient quantity, will fill a whole building very quickly.

In my own house, that I’d lived in 9 years, I had great difficulty navigating. A stranger would have been completely stumped, so too would a burglar in an artificial fog.

As to the risk of a release during a fire. From personal experience the smoke is already so bad that adding a water/glycol fog to it wouldn’t make the situation significantly worse. As far as this hindering fire fighters – they already train to work in 0% visibility and I’d suggest that this represents the interior of most domestic fires. Remember the old adage: “It isn’t the fire that kills you, it’s the smoke”.

Nothing beats experiencing it first hand to drive home how quickly and effectively smoke turns familiar surroundings into alien, unnavigable territory. On that basis I’d suggest that the ‘fog alarm’ would be highly effective and that Bruce has it very wrong on this occassion.

Anonymous June 21, 2007 9:25 AM

That had a system like that on the tv show “It Takes A Thief”. It looked like it worked pretty good.

David Mason June 21, 2007 9:26 AM

This is common at IT places in the UK where they store sensitive information. It works ok, as in you can see this: [ ] when it goes off.

It does leave a ‘residue’ when it locks on too long though. They tend to couple it with very loud noises and flashing lights. We had ours say ‘A gas has been released. Please remain still and you will not be harmed’ – which I imagine would scare the bejebus out of anyone carrying a monitor, though they might drop it.

Not sure about the wiseness of home use.

PS Bruce just revealed his humanity in seeing this for the first time – better strike of omnipotent from the list then…

brainfart June 21, 2007 9:28 AM

I remember reading about an even better security system: polyurethane foam. The two component foam is stored under pressure in doors or walls. If the containers are punctured (or if the alarm system is striggered) the corridor would immediately fill with thousands of agllons of very sticky, hard, quicksetting PU foam. This was seriously investigated as a security system for government and military installations, since it can effectively defend against a huge numbers of attackers. It can also trap or even kill them under certain circumstances, and the foam will afterwards need to be removed mechanically since it adheres to pretty much anything.
THATS what I call an effective security system!

Rich Wilson (formerly just Rich on older blog posts) June 21, 2007 9:28 AM

All those ‘false alarm, I can’t get out of my house’ problems go away for blind people.

Rich Wilson (formerly just Rich on older blog posts) June 21, 2007 9:45 AM

Or better yet, actual kids. Sure worked for Mcauley ‘Kevin’ Culkin.

Michael Jagger June 21, 2007 10:11 AM

The two biggest reasons that this is a goofy product, especially in a residential application are that a) 98% of all alarms are false, and b) most people have an inordinate delay time on their alarm system to begin with.

The best protection comes from having an alarm system that is designed properly (to detect someone while they are trying to get in, rather than once they are already in), has quick, private response and the most valuable items are ‘five minute proofed’.

The fog systems are best deployed in a commercial setting, ideally in a small vestibule or other room. Even then, I would never try to sell one to a client…

Patrick Farrell June 21, 2007 10:25 AM

My wife and I talked about getting a home security system. All the salesmen we talked to played the fear card immediately. The last guy we talked to was a straight shooter. He said:

1) The best alarm is one that’s loud and lights up your house and yard. It sucks to wake up the neighbors, but that’s what will scare off an invader.

2) Odds are, the police are only going to show up soon enough to have you fill out paperwork.

3) Any alarm system can be compromised by cutting your telephone line (unless, of course, you upgrade to our deluxe package which uses a dedicated cell phone)

In the end, we inherited my Mom’s 100 lb dog and he provides us more security than any of these systems ever could. Plus he’s a lot more lovable.

GiggleStick June 21, 2007 10:30 AM

I like the similar device that fills the room with immobilizing foam so they have to chip the crook out with a chisel.

fogged June 21, 2007 10:39 AM

It does work. I was once in a security exhibiton where they fogged a room and you had 30 sec to find 6 tokens. If you achived this you got $500. The room had also some furniture in it. My result: 5 tokens and a brusied knee. I smashed my leg into the havy tresor while retrieving the last one.

During the whole exhibition nobody was able to get all six tokens.

Brian Carnell June 21, 2007 10:41 AM

Hmmm…if this goes off in my house with a burglar, he or she is more than likely going to kill himself tripping over all of the toys my kids have left everywhere. Would deploying this with that knowledge expose me to additional liability? 😉

Andrew Gumbrell June 21, 2007 10:42 AM

“I like the similar device that fills the room with immobilizing foam so they have to chip the crook out with a chisel.

Posted by: GiggleStick at June 21, 2007 10:30 AM”

… but what about them having to chip you out with a chisel when the thing goes off at the wrong time?

Pat Cahalan June 21, 2007 10:51 AM

Someone already mentioned fire; an earthquake would be another problematical exception scenario.

I agree Alex and Mr. Farrell, a dog is a much more effective home security solution. It doesn’t even need to be a big dog, just one that will bark at strangers.


bought off with a steak?

Really, dogs are most effective as alarms, not as weapons. My dog is super-friendly and slightly spastic, about the only threat he would pose to an intruder is that he’d jump all over him/her and maybe nose them in the unmentionables a few times. However, he would bark like crazy if anyone ever approached the front door, let alone tried to get into the house.

You maybe could distract him by offering him food, but you’d have to get close enough to offer and get preliminary access to pass him the steak, and he’d bark like a nut for the 2 minutes it took for you to accomplish this task, more than enough time to wake me up 🙂

Citizen June 21, 2007 11:01 AM

@brainfart, Re: Polyurethane foam.

Sounds like life imitating art, to me: some time circa 1982, one of the Judge Dredd story arcs in ‘2000AD’ had the Judges using quick setting foam, sprayed from helicopters, as a ‘crowd-control’ measure.

I suddenly feel extremely nerdy for remembering that particular comic story after all these years …

sarcasm June 21, 2007 11:35 AM

The problems with this idea outnumber the possible benefits.

When the criminal breaks a leg trying to escape, sues you for $30 million, and actually wins because of the dopey US “justice” system, he’ll laugh all the way to your bank account.

Even worse, your 5 year old sets off the alarm accidentally during one of your fabulous, famous cocktail parties. When one of your guests falls, breaks a leg, sues you for $30 million, and actually wins because of the dopey US “justice” system, you’ll have to tell them to go see the burglar who sued you last time.

What if you’re at home when the burglar breaks in? Now you’re stuck in the fog with the burglar and your family. How will you know whom to blow away with that big old Smith & Wesson?

paul June 21, 2007 11:47 AM

The purpose of security systems is to prevent loss. Keeping an intruder from getting away with valuables is an important part of that, but if I come home to find all my windows broken by a burglar trying to ventilate the place, all the furniture smashed up and every exposed surface in the house in need of cleaning, I’m not sure how much I’ve gained. It’s like wearing a dynamite vest to deter muggers.

Andrew June 21, 2007 11:49 AM

Thank you for posting on subjects I usually don’t get to talk about.

I love the fog system. Firefighters can just get out the infrared and function as usual. The bad guys are going to find it a struggle to escape, and if so, empty-handed.

If the containers are punctured (or if the alarm system is striggered) the corridor would immediately fill with thousands of agllons of very sticky, hard, quicksetting PU foam.

HUSH! This is a deadly system. The only conceivable use I could think of would be in protecting objects that can be protected by lavish amounts of deadly force. I’m sure that the Department of Defense and Department of Energy can think of appropriate applications.

Aze June 21, 2007 11:54 AM

@David Mason

Bruce’s problem is that he sees the fog as a form of light encryption and thus transparent. He wasn’t analysing at as a security measure against normal humans and he’d never realised that the demos he saw were meant to be security devices.

Roy June 21, 2007 12:05 PM

It would help the general good to make the stuff not look like smoke from a fire. Their fog is whitish, which could be mistaken for white smoke. Why not add a dye — hot pink or neon purple? First responders would then know immediately that this is not a fire.

If accompanied by strobe lights and screaming alarms, the cops would know the obvious thing was to cover all the exists and bide their time.

Sez Me June 21, 2007 12:24 PM

@Roy: “Why not add a dye — hot pink or neon purple?”

Dye would probably stain walls, furniture, and/or carpet.

Hellfire June 21, 2007 12:29 PM

@Sean Cleary

Exactly what I was thinking. Now when the police arrive, there will just be a bunch of panic and confusion. I could easily see them not properly identifying the fog as artificial and getting the fire department to come, meanwhile the badguy slips away. Even if that doesn’t happen, you are just giving the badguy cover.

Werner Ackermann June 21, 2007 1:18 PM

This is a very effective system IMHO. My brother has a similar system installed in his one-car garage, but one that sprayed tear-gas. It was a simple motion-sensing system, that he forgot to turn off one morning. The resultant spray got him coughing out of the garage in record time.

He couldn’t get in or near the garage for at least another hour, and was late for work, but he didn’t lose anything precious.

This system just seems less hazardous. Perhaps slightly toned down versions might be available for more focused installs. A few 240 m^3 units would be plenty for protecting many houses.

Upside of this system, since you know the terrain better, you have a slight advantage over the trespassers.

The down-side of guard dogs is that they can get poisoned. We had quite a few cases in the neighborhood where dogs were killed. Poison is cheap, and even if they don’t break in, the loss of a loved pet is sometimes worse than losing use of your house for 45mins to an hour.

This system might not be perfect, but it seems more effective than a mere alarms + response system.

I can’t see why Bruce would see it as ‘a bad thing’. Care to enlighten us?

Ohsay Canusee June 21, 2007 1:26 PM

Gee…lets see. Burgler breaks in. Fog goes off. Burgler crawls to back of room and sits down. Police come in 10 minutes, but fog doesn’t clear for 45. Hmmm…

How do you catch the burgler again?

Or do you expect the police to wait around?

Fog clears, police have come and gone, and burgler has plenty of time to “clean house”.

David Donahue June 21, 2007 1:43 PM

Most of what i had to say is already said, however I do just have to add:

“If you think that blinding fog will solve your problems, then you don’t understand blinding fog and you don’t understand your problem.”

Woody June 21, 2007 1:49 PM


Yep, firefighters will see the white smoke, realize it’s not a fire (wrong color), and break out the infrared gear and proceed as usual for a cold-smoke environment. This is exactly what we train in. And without the camera, you can’t see you hand in front of your face, even with the lights on. Kill the lights and you see nothing at all. It’s very disorienting, until you close your eyes.

But an infrared camera sees right through it. If the CCTV system was IR (and if it should work at night, it should be), then it would go right through the fog as well.

Indelcio June 21, 2007 1:54 PM

Why does Bruce call it silly?

Out of all the comments in this thread, only one other person has managed to point it out; rather sad for readers of a security blog. So I’ll point it out again.

It’s real-life Security Through Obscurity.

David Donahue June 21, 2007 2:14 PM

I just had a thought; My neighbors are a blind couple. As a security system for them, its an easy trade-off.

When assaulted in their home or during a home invasion it levels the playing field against attackers. During a not-home burglary it would act as a good deterrent. Heck, add in the strobes while you’re at it.

Of course in the event of a false release, or even accidentally triggered release during a fire it would have minimal effect on them.

Sounds like a niche product to me, also of course it’s cool and non-lethal so it’s market includes gadget lovers like myself.

As a kid I once lived in a house that had motion / infrared sensors in the corridors. You could hear them “click” when you tripped them, even when the system was not armed. I got very good at not tripping them by a variety of tricks. My favorite was blocking the infrared beams with an object held in front of me that is the same as the ambient temperature. You can just imagine 12 year old me, spraying hairspray in the darkened hall (to see the beams) while crawling on my belly to my room every night, later hearing from my parents “why is the hallway carpet always so sticky?” Fun times, fun times…

Anonymous June 21, 2007 2:14 PM

It’s real-life Security Through Obscurity.

I don’t think so. Much better analogy would be blocking account after several unsuccessful login attempts.

The Thermographer June 21, 2007 2:32 PM

@Woody: How is it that an IR camera “sees right through it…” (fog)?

Infrared cameras detect heat differences (delta’s). If the fog is room temperature, and the surface areas of the room are room temperature, then you will see nothing of any interest on your monitor. Including furniture.

You could find the warm body of a burgler by stumbling around in the fog and getting up close…provided you don’t trip over the coffee table and break your leg.

If the initial release of the fog is cooler than normal room temp., then the furniture would be “visible” to the camera…but once that fog warms up (and it shouldn’t take too long) you’d be “sightless” with IR gear.

Schnuce Breier June 21, 2007 2:41 PM

“The basic cost of FogSHIELD is $4,200. It is mandatory that FogSHIELD be installed by an authorized alarm/security company.”

So the total cost to outfit my house would likely be at least $5,000 USD and it probably requires some periodic maintenance or testing. There’s no deterrent component (maybe a “Protected by FogSHIELD!” sticker) so a thief has little incentive to move on to my neighbor’s house instead of mine. There would still be property damage, even if the thief were caught.

Since I have a modest house containing few things of material value to a thief, this would not be a very good security investment for me. I could probably make a better case for purchasing some of those motion detecting robot dogs.

Nostromo June 21, 2007 3:22 PM

@people who mentioned dogs:

Dogs are completely useless as ‘security systems’. (1) They bark when there isn’t a burglar, so neighbors ignore them, (2) they really can be silenced with food (any meat will do – needn’t be steak. Try it on a noisy neighborhood dog). To be absolutely sure, a burglar can put knockout drops in the meat.

I think Bruce has got it wrong about this home security system. Will he admit his mistake? or give a reason why he called it ‘silly’?

X the Unknown June 21, 2007 3:27 PM

This might be an acceptable security measure if it were implemented in such a way that it was only enabled when nobody was (supposed to be) home. Of course, it still has to automatically alert the authorities.

That way, issues about being trapped in the fog with a scared intruder, or trigger-happy cops, don’t apply. That’s probably one of the more common conditions under which serious burglary happens, anyway – the “bad guys” scope out your house and notice the family leaving with a pile of luggage, or otherwise acquire info suggesting nobody will be there.

When the “Fog-Alarm” triggers, it should automatically disable the (particulate based) fire-alarm for some period of time…or better yet, use it’s own particulate sensor to determine when to re-enable the fire-alarm.

If you really feel this would significantly add to the problems in escaping/fighting a house-fire, add a reciprocal circuit: disable the Fog-Alarm when the Fire-Alarm goes off.

Of course, all this is going to cost a lot; you have to do a cost-benefit analysis to see if it is worth such an installation for use only when nobody is home.


As somebody pointed out earlier, a dog with a “good bark” is a pretty cost-effective burglar deterrent. Several years back, we had a rash of break-ins, where every house on our block was hit – except ours, and the neighbors to each side of us. The cops credited our dog with preventing burglary at these three houses.

Christoph Zurnieden June 21, 2007 3:58 PM

Infrared cameras detect heat differences (delta’s). If the fog is room temperature, and the surface areas of the room are room temperature, then you will see nothing of any interest on your monitor. Including furniture.

You will always have some temperature difference, it depends on the resolution of the camera if you are able to get an image.
For burglars who are short of money—probably most of them—I would propose a small torchlight build from a switch, a battery and some IR-LEDs.

But both of it depends on the wavelengths of the filter, the glycol-water-fog, which are unknown.


dragonfrog June 21, 2007 4:36 PM

@ X: I don’t doubt that dogs are effective at deterring burglars. But cost-effective? In a cost-benefit analysis of a dog as a burglary prevention device, the benefit side might look something like:

(average cost of a burglary) X ((average burglaries per annum w/o a dog) – (average burglaries per annum with a dog)

And the cost side like:

annual cost of dogfood and supplies + (value of all your furniture) X ((annual depreciation rate of furniture with a dog) – (annual depreciation rate of furniture w/o a dog))

Of course, that’s ignoring non-material property related benefits of owning a dog, like they’re such charming animals…

Kevin June 21, 2007 5:27 PM

The comments about “IR” are actually conflating “FLIR” which displays the temperature difference between warm (human body, shorted wires) and cold (furniture, fog) objects and costs $6K-$30K per camera, with the more common “Night Vision” IR which relies on detecting near-visible infrared and costs just a few hundred dollars at most, and usually requires an “IR illuminator” such as the LED you find in your TV remote.

Many fire departments have invested the money in FLIR (infrared thermography) because of how very useful it is at spotting hotspots and other fire-fighting tasks.

Some police forces are using either FLIR or more primitive (and affordable) heat sensors because of the obvious LE applications of spotting body heat.

bob 2.0 June 21, 2007 5:29 PM

Despite the testimonials, this can’t possibly be an effective security system.

It doesn’t include mirrors.

Real Security Gurus(tm) all know that Real Security(tm) requires smoke AND mirrors. Smoke alone is completely inadequate.

Case closed. Pfft.

Pat Cahalan June 21, 2007 6:34 PM

@ Nostromo

Dogs are completely useless as ‘security systems’.

I disagree, and, um.. your following statements are somewhat flawed.

(1) They bark when there isn’t a burglar, so neighbors ignore them

This can be corrected with training, but regardless they can still effective warn the owner that someone is approaching the house.

Yes, burglar alarms as alerting forces work when you’re gone on an extended vacation (unlike a dog, whom you’ve either kenneled, taken with you, or housed with a friend), but dogs are certainly a major deterrent otherwise; generally speaking a burglar would be more likely to choose a different target than circumvent the dog. Sure, it doesn’t prevent home burglaries, but at least it’s not my house they’re breaking into 🙂

(2) they really can be silenced with food

This only works if you have access to pass the dog the food (I noted this above).

If you have an indoor dog, the burglar needs to gain access to the house in order to bribe/drug the dog. Someone would have to get in through my front door in order to pass my dog tainted meat, and he’d be raising a ruckus the whole time.

@ bob 2.0

That was brilliant.

Stefan Wagner June 21, 2007 6:45 PM

Big benefits: It doesn’t smell like a dog, it doesn’t sound like a dog and it doesn’t behave like a dog – it’s not a dog at all.
– scnr – I like cats 😉

Without knowing how it works in detail – just guessing: Perhaps an attacker might cut it’s power-supply, but he needs to know about it.
Perhaps because he did some social engineering before, or perhaps it’s his second attempt 😉

Of course it’s not a good device, if you are at home, but a lot of burglars avoid such a risk.

If you install such a device, you know before:
– Do you have a firedetection system, which could get confused?
– Do you have kids, which could cause false alarms?
– Does your inventory legitimate the costs?
(- Do you like dogs?)

Hellfire June 21, 2007 7:13 PM

Dogs are tried and tested security measures used for ages by law enforcement and security guards. I think money spent on a trained guard dog that can think and adapt to situations is much better spent than $4000-5000 on a fog machine.

My question is: are the disco lights included, or must you buy them separately.

RC June 21, 2007 11:13 PM

I must now announce that I have invented a digital version of that fog security device. Whenever someone suspicious is reading your website, a digital fog quickly covers the text of the site, making it somewhat more difficult for them to read it. It’s basically the same thing, so I’m hoping it’s not a patent infringement.

Shad June 21, 2007 11:26 PM

Sez: The solution for the dye is to make it disappear. There is a concept toy claimed soon to go on the market – colored bubbles. They use a leuco dye that turns into colorless form easily. See here:

To see through the fog one needs to use wavelengths that do not undergo Mie scattering on the particles of the fog. Conversely, one can allow or disallow uses of optical or infrared or thermal cameras by carefully selecting the droplet sizes the fog generator makes, potentially allowing the CCTV system to not be disabled. A fine-particle fog that lets infrared and perhaps also red light through unscattered, illuminated by a blue stroboscope, with blue-excluding filters on the camera lenses, may effectively blind the humans on the scene while leaving the camera systems unaffected. Also, if you have control over the particle sizes produced by the system, you can tailor the smoke detectors to be blind to just precisely that size of particles. A further measure to prevent coalescing of the particles, eg. making them electrically charged to repel each other, may be beneficial there to stabilize the particle sizes over time.

bad Jim June 21, 2007 11:38 PM

If systems like these were widely deployed, serious burglars would simply equip themselves with inexpensive night vision devices. I’m not sure that a digital video camera wouldn’t suffice, perhaps augmented with an IR light source.

Adrian June 22, 2007 12:15 AM

There’s an electrician’s business around the corner from our house that sells these fog systems. My wife was going to work one day and saw all three or four employees standing around out on the footpath and massive amounts of fog billowing out of the loading dock — I guess someone let one off by mistake.

David June 22, 2007 3:25 AM

This is for real. I’ve seen it demonstrated in an RV in the carpark at an infosec show in England. It’s very effective.

I know several companies that have installed it, one got burgled about a week later and the police found the guy curled up under a desk, totally bewildered.

ThiefInTheNight June 22, 2007 4:36 AM

So the normal method of setting the (false) alarm of time and time again untill its disabled would work even better (what are the costs of a reset?). If you just spent 5000 you proablably have something worth stealing.

Back at high school the girls doom rooms were set up with a alarm. It would light the whole area and sound a rather loud alarm when it went off. Well the boys couldn’t get in and the girls couldn’t get out… What did we do? It was one of those microwave motion sensor things (we think) because small stones warped in Al foil would set it off (useing a slingshot).

the first night it took 4 false alarms to turn it off. The second night it took 2 false alarms.
It wasn’t turned on again.

Oh and as for steaks working with a dog. That would only work with a pet. Any properly trained dog will not eat food from a stranger. This is not the movies…..

Mark June 22, 2007 5:53 AM

Oh and as for steaks working with a dog. That would only work with a pet. Any properly trained dog will not eat food from a stranger. This is not the movies…..

Mythbusters covered this one, as well as other ways to distract a trained dog. Whilst a trained dog might take food offered by a stranger it’s only distracted as long as it’s eating and dogs generally do not have infinite apetites.

payingalimonywhileunemployed June 22, 2007 6:53 AM

@sarcasm: Why do you think they call it a “criminal” justice system… It’s criminal to call its output justice.

ThiefInTheNight June 22, 2007 7:45 AM

Sorry but mythbusters is all about entertainment. Don’t take anything they too as proof of anything.

Salmon June 22, 2007 9:37 AM

I feel sorry for our American friends who are worried about lawsuits from an injured intruder.

Anonymous June 22, 2007 10:53 AM

“Sorry but mythbusters is all about entertainment.”

We have the pronouncements of a random stranger on the Internet by the name of “ThiefInTheNight”, and then we have the testing done by a highly regarded source:

They lay out their testing protocol right before you and do it. If you have complaints with their methodology, you might wish to take it up with them. Until that happy day, I’ll accept their results over your mere assertions.

And finally, since you don’t seem to “get it”, I guess it has to be spelled out in detail. MythBusters is not “all about entertainment”. They are about core science amplified to entertainment levels.

Jordan June 22, 2007 12:29 PM

Thought the enclosed information may address some questions or concerns.


Prior to installation, the local monitoring, police and fire station are notified by a certified letter that a FogSHIELD unit is being installed.

Actual Burglary: Monitoring station immediately station notifies first responders of security fogger on premises. In addition, there is Signage placed in storefront or residence windows to further notify first responders of security fog device.

Egress: Unit is installed in rear of store pointing towards the intruder’s possible entry point.. Once triggered, the unit ejects the non- toxic fog towards the front of the store. The intruder simply exits the same way they entered.

Egress Fire laws; were written mostly for door lock systems that have the ability to lock someone in the premises. Security fog technology was not even available in the states when those laws were written. We feel its essential to educate the fire associations on the numerous precautions and safety measures regarding security fog technology.

Fog Facts – FogSHIELD FAQs

What is FogSHIELD and how does it work?
FogSHIELD is a unique addition to a security system that stops burglars in their tracks by rapidly ejecting a dense harmless wall of fog– drastically reducing the intruder’s line of sight.

FogSHIELD connects to most existing alarm systems and is triggered by a motion sensor or door trip. Upon activation, FogSHIELD rapidly ejects a harmless dense fog blanketing a 2,000 square foot space in less than 15 seconds. The fog is non-toxic and is guaranteed to leave no residue. Within 45 minutes of activation, the fog will have fully dissipated without leaving a trace of residue.

Do I need to be concerned that FogSHIELD will false trigger?
If integrated properly with an alarm system, FogSHIELD will only trigger when a specified series of programming options are tripped in succession. An installing dealer will ensure that FogSHIELD is strategically located so that it fully protects high risk assets and is part of a sequential intrusion detection-designed configuration.

FogSHIELD will only trip when the primary alarm system is activated. If the alarm system is deactivated for the day, the FogSHIELD system can not expel the fog. Only when the primary security system is activated will the localized motion sensor be become active. FogSHIELD will only dispense the fog if both the primary security system and the secondary motion censors are tripped in succession.

What is the pricing for FogSHIELD?
The base cost for FogSHIELD is $4,200.00. It is recommended that FogSHIELD be installed by the service technicians associated with the existing primary alarm system. FogSHIELD technicians would be happy to work with the security company to assure that FogSHIELD has been properly installed and all sequential detection systems are functioning and aligned properly.

Can I install FogSHIELD myself?
FogSHIELD products are installed by a certified technician only. In order for all warrantees and product service agreements to be valid, the unit must be installed by a security system technician. The installation process is extremely quick and non-disruptive, taking about two hours.

How often do I need to replace the fog ejection cartridge in my FogSHIELD?
Fog cartridges are designed to last approximately five years and each cartridge contains enough fog for 15 ejections. FogSHIELD cartridges are easily replaced by the property owner or a security company technician without mess or difficulty. To replace the FogSHIELD cartridge, simply open the side panel and remove the old cartridge, then replace with a new cartridge. From start to finish, fog cartridges can be replaced in minutes. Additional FogSHIELD cartridges can be easily ordered through the FogSHIELD website(link to order page) for a cost of $ 199.00.

What type of maintenance do I need to perform on my FogSHIELD?
FogSHIELD requires virtually no maintenance. The FogSHIELD unit has an easy to read LED light panel which clearly indicates when fog cartridges are getting low or the battery is in need of replacement.

What if I relocate, can I bring my FogSHIELD with me?
FogSHIELD can easily be relocated to a new home or business. It is important to have the unit re-installed by a representative of the security system in place at the new location. FogSHIELD staff would be happy to assist with any necessary relocation arrangements.

Mike June 22, 2007 1:25 PM

My principal worry would be armed men with guns looking through my house for a burglar, especially if my family or myself were in the house asleep when it happened.

And the “FogShield will only go off if your principal alarm system goes off” statements don’t do much to convince that false alarms don’t happen. I have friends that never use their alarm systems anymore because the company was going to start charging them for every false alarm, and their were many. June 22, 2007 2:05 PM

Please read the carefully.

It doesn’t matter if the alarm system “trips”, the fogger still will not eject until a series of pre-determined motion sensors are activated. The sensors are installed in conjunction with the fogshield.

BTW: Many homeowner (not businesses) opt to trigger the unit manually via supplied wireless remote. Works great if you have a panic/safe room.

Go to and you can review a actual surveillance video where FogSHIELD once again stopped a burglar from steeling thousands of dollars from
1600 store retail chain. VIDEO IS LESS THEN 45 DAYS OLD.

Upwards of 98 % of security fogger false alarms are due to incorrect installation procedures. Can a false alarm occur? yes anything is possible, however the benefit seems to overwhelmingly out weigh the rare false alarm.

Their is no question FogSHIELD is not for every application. But if you were ever the victim of a burglary.. you will certainly appreciate
this device.

Thanks for allowing me this opportunity to respond.

Xellos June 22, 2007 4:23 PM

A simple upgrade to this would be to dope the glycol with a dye that fluoresces under UV light and is colorless otherwise. Then even if they get out and run away they’re covered in an obvious tag for anyone looking.

Anonymous June 22, 2007 4:28 PM

This type of system has been used in retail stores and police “bait cars” for years… I remember seeing media snippets on this back in the mid-90’s!

It seems as if the drive for “innovation” for DGS et al is making lots of old ideas appear new again…

Anonymous June 22, 2007 7:15 PM

@Mark: “Whilst a trained dog might take food offered by a stranger it’s only distracted as long as it’s eating and dogs generally do not have infinite apetites.”

Most good-sized dogs also eat at a really prodigious rate (literally gulping down huge chunks of food). That nice steak will probably last much less than a minute. It could set you back quite a bit to buy enough meat to keep a dog busy long-enough to burgle a house.

Sure, they are “dumb animals” – but a dumb animal is still vastly smarter than the brightest automaton ever made. Dogs are territorial, and develop a vested interest in protecting “their” property from intruders. The can and do evaluate situations and perform rudimentary analysis and planning. They continue working even durring a power outage. A little training takes care of most of the “false-alarm” situations – and they recognize and react to situations never even considered by the “alarm installer” (owner).

That said, they are by no means the be-all end-all of security. Dog do require continual maintenance and upkeep, as somebody pointed out above. They are vulnerable to certain classes of “workarounds” that don’t affect electro-mechanical devices (poisons, for example).

However, if you’re considering owning a dog, “alarm system” is one of the things to put in the “pro” column of your pros & cons list. Most family-pet dogs can be OK at sounding an alarm when intruders get near, but shouldn’t be relied upon to actually attack or hold intruders. That sort of behavior requires either intensive (and expensive) training, or a very aggressive dog (so much so that you might not want it around your family).

Anonymous June 22, 2007 7:24 PM

[Bruce asked me to post this, but I’d prefer to remain anonymous for reasons that are probably obvious.]

I recently had the pleasure (?) of inspecting a site which used a fogging system (not the “fog-SHIELD” brand), after a burglary attempt. This site is used to store large quantities of RAM and retail boxed microprocessors, whose cost rival their weight in gold.

They referred to the system as a “smoke projector”, and in this site, there were several of the fogging devices, combined with very loud intermittent sirens at discordant frequencies and some strobe lights, which apparently illuminate the fog, adding to the disorientating effects. The site itself was a despatch warehouse, with the usual steel racks, stacked with products.

This company had installed the system after several “ram-raid” attacks had removed a lot of stock before the alarm response team could get to the premises. After the second such robbery, this had cost them their insurance coverage. In this instance, an external door was opened by crashing a stolen car into it. The system triggered 90 seconds after the silent activation of the alarm system.

The aftermath was:

  • A clear sticky deposit on all the surfaces, up to about 0.5 mm thick and with an odd tackiness, kind of like a nightclub floor.
  • An unusual smell.
  • Several pools of vomit, including two that ran over some distance, as if produced by someone moving at the time.
  • Two patches of blood and matted hair, one on the corner of a storage rack, the other on the concrete wall beside the door, consistent with moderate head trauma.
  • One streak of blood on a floor and wall, of indeterminate origin.

  • They were advised to replace the filters on their air-conditioning system.

No one was apprehended when the alarm response team got there, but no goods were taken either. The building was inaccessible for roughly an hour after the alarm triggered, and I’m told (didn’t observe first-hand) that the fog remained very dense for most of that time, and then appeared to clear suddenly. Being a warehouse, the site didn’t have much ventilation, however.

I’ve since been told that some people experience nausea from prolonged exposure to discordant sirens, and so that may not be a direct result of the fogging devices. But having seen the consequences of deploying such a system in a large, open warehouse space, with a simple geometric layout, the idea of installing such a system into residential premises just seems completely insane.

Clive Robinson June 23, 2007 6:40 AM


“no goods were taken either.”

Sounds like it worked the way it is supposed to work…

One point though, did the Police take samples of the vomit / hair / blood for DNA matching ?

If not then they where not up to the job the community is paying them for (these criminals most likley had connections to serious organised crime as it needs those sort of connections to safely shift large quantities of CPU/RAM chips).

Not all fog systems leave an obvious or in some cases (easily) detectable trace after a reasonable period of time. Those that do are not suitable for all environments.

As for Bruce’s “Silly Home Security” it is an unfortunate generalisation he made and people have taken justifiable pot shots at him for it (But I suspect his skin is quite thick enough from previous pot shots 8)

It realy depends on the home, if you have a little place in SmallTown.SomeState.US which has no items of value either in cash or sentimentality and you have 2.7 kids and 1.75 dogs running around then yes it does not make a whole lot of sense as an ordinary loud alarm and a few flashing lights will be more than any insurance company is going to want, and the only real downside is less than friendly neighbours if it goes off on a regular basis.

But the minute you have things either of value or sentiment then it starts to make sense.

For instance lets say you have been left a couple of bits of furniture and a few plates etc by an old aunt or grandmother. They might not be of any real intrinsic worth but emotionaly how much are they worth to not be stolen or smashed?

Afterall they cannot be replaced, and it might be all you physically have left of a very treasured relationship, and what has the loss done to the treasured memories as well?

Also there is a point people often forget, that some house breakers are there not to steal but to commit other crimes such as urinating and deficating on people furniture walls etc or worse.

Also some house breakers also set fire to the place just to cover their tracks etc.

Think of the peace of mind a woman living on her own is likley to get from knowing that an intruder is unlikley to be in a fit state to physicaly abuse her in the unlikley event that they get close to her…

I suspect the cost of cleaning up any traces of the fog is going to be a lot less expensive than smoke and fire damage, and emotionaly much better than trying to clean out the thoughts of what bodily secretions the purp has left on your everyday items or you?

And before anybody asks no I have absolutly nothing to do with the sale of alarm systems for homes etc.

stefano June 23, 2007 8:05 AM

drawbacks from what i understood :

-inaccessibility of the site for a period of time
-Possible physical damage to persons (employees, owner, intruders etc.)
-Damage done by blinded intruders
-Damage done by the smoke on furniture (even if the contrary is claimed)
-False alarm during an emergency situation could lead to more damage than without
-A burglary could trigger an inappropriate response, Ie having firefighters coming instead of police, which could lead to more damage than stolen goods.
-Prepared burglars could still stole goods.

@Clive :
I don’t really see this deployed in a house… especially not while people are living inside.
In other cases this system maybe cheaper than reinforcing doors and windows or having a safe ?

Bruce Schneier June 23, 2007 11:13 AM

In the comments, a lot of people have taken me to task for calling this security silly. I stand by my statement: not because it’s not effective, but because it’s not a good trade-off. I can certainly imagine scenarios where filling your house with vision-impairing fog is just the thing to foil a would-be burglar, but it seems awfully specific a countermeasure to me.

Home security — like all security, really — is a combination of protection, detection, and response. Locks and bars are the protection system, and the alarm is the detection/response system. Fogshield is a protection system: after the locks and bars have failed, Fogshield 1) makes it harder for the burglar to navagate around the house, and 2) potentially delays him until the response system (police or whomever) arrives.

But it has problems as a protection system. For one, false alarms are way worse than before. It’s one thing to have a loud bell annoy the neighbors until you turn it off, it’s another to fill your house with fog in less than 15 seconds (plus the cost to replace the canister).

This whole thing feels real “movie-plot threat” to me: great special effect in a movie, but not really a good security trade-off for home use. An alarm system is going to make an average burglar go to the house next door instead, and a dedicated burglar isn’t going to be deterred by this. June 23, 2007 3:41 PM

Hi everyone,

It’s truly a shame so many of the various comments are unfounded and stated by persons with zero security fog experience.

My firm ShatterGARD is the largest privately held glass protection firm in the US. Our products BlastGARD and VehicleGARD are utilized by the US military in Iraq and have saved countless lives. To that extent to think for a second that we would market a product that could possibly harm another human is just silly.

Anyway thank you all/

PS: Bruce- thank you for your wonderfull site.


PS> Should anyone desire to see a Fogshield unit in action..just contact me.
See it with your own eyes before you pass judgement. NON-TOXIC and 100 % ZERO RESIDUE.

RonK June 24, 2007 12:33 AM


To that extent to think for a second that we
would market a product that could possibly
harm another human is just silly.

Even food and water can “possibly harm another human”…

The people reading this blog are mainly sophisticated security researchers who realize that everything, no matter how innocuous, has a non-zero probability of causing harm, and that the major difficulty in security is to be able to estimate the risks involved vs. the benefits.

I advise you to stop posting while you only look clueless, rather than mega-shill-like.

Christoph Zurnieden June 24, 2007 1:15 PM


To that extent to think for a second that we would market a product that could possibly harm another human is just silly.

I would go even further than RonK: your products actually harmed other humans.

Our products BlastGARD and VehicleGARD are utilized by the US military in Iraq and have saved countless lives.

The saved lives are the lives of american soldiers in almost all cases, is that correct? Some of these soldiers have killed humans later, which they couldn’t have done, if they were killed in the first place.
Some dictator may have survived an attack because of one of your products and killed several thousand people later as an revenge for that attack.
Farfetched? No, Jordan, it’s just the other side of the medal. And if you are a bit more familiar with th difficulties of practical security you would meditate a bit about the rim of that medal.

See it with your own eyes before you pass judgement.

Any change to do so in Germany?
Will I be allowed to measure the characteristics of the fog when it acts as a filter for photons, electromagnetical and sound waves?


Is there a proof for that very bold statement?
Is it save to use it for food? Caviar and truffles are not very cheap!
Is it save for living fish? There are some colorfull japanese carps that can get very expensive!

and 100 % ZERO RESIDUE.

You are using drops of a glycol-water-mix, that means, that some of it might deposit on some surfaces for some time > 0.

The canisters in use have more than one “shot” in it. What do you do against biological infections? These might stink quite awfull, y’know?


Christoph Zurnieden June 24, 2007 4:29 PM

Non-toxic does not mean edible.

Does that mean that you are still testing new restaurants?

But you are of course correct: I should have made my point more clear that the statement “non-toxic” is useless without supporting formal tests by a neutral medical laboratory.


Chris Smith June 25, 2007 1:32 AM

I’ve had my house robbed more than once, and I can tell you that the difference between “broken into” and “robbed” is the amount of effective time someone spends there. Although not all police officers will agree, many note that an alarm simply puts a burglar on a schedule. They know they have between two and five minutes to find something and get out.

Bruce, in your list of the effects of FogShield, I think you missed the most important one — it “shields” everything with “fog”. I actually think the navigation and burglar delay factors are negligible parts of the protection.

Fogshield cuts that schedule of finding something to 15 seconds; likely even less than that, as someone would see the fog coming almost instantly and be distracted. Once they can’t see, their priority is likely going to be getting out, because that will use up several minutes they weren’t counting on.

Note that under most circumstances, the unit only fires when an intruder is in the house. In this case, the cost of the refill must be weighed against the loss. Given a choice between replacing one or more possessions with a value range that might be significant – or replacing a cartridge designed to be replaced if used – I’ll choose the cost of the cartridge. It’s like a bicycle helmet — replace it if you use it.

Furthermore, most burglaries are NOT when people are home. That’s treated as a personal attack, and most burglars don’t want to attack anyone, they just want goods to sell. There’s no profit in attacks. I’m not worried about my house filling with fog for a couple of hours when that’s likely the time it will take for me to get home anyway. There’s no loss of use if I’m not going to use it.

The issue of false positives appears to be mitigated by requiring a professional installer. This goes a long way to ensuring that it only fires when it should. I’m not in a position to assess the left-over residue, but reducing that appears to be a focus of this product, rather than a side-effect they were content to live with.

Even if you are in the house, you can just sit tight. YOU don’t need to leave in a hurry. Although a false positive is unpleasant, it doesn’t appear to be either fatal or even illness-inducing. At least one video shows a person just standing there while he is enveloped in the fog.

Although there will still be a “determined burglar”, becoming one is significantly more costly if this system is in place. Either you need costly countermeasures — and having to explain why you are walking around with funny looking military style goggles — or you need a significant expenditure to determine how to quickly get what you want either by advance mapping or bribing someone on the inside.

By comparison, the cost, although not small, is well within the range of many householders. It’s likely only twice as much as some insurance deductibles. It’s less than many used cars. I expect that a good insurance company would give a better than average discount if you had this installed.

An alarm system will make some burglars go next door. But some will still ignore the alarm, trigger it as they break in, and grab what they can in two minutes. That’s opportunistic, and it’s usually hard to deal with that threat. We tend to frown on alarms that are fatal to the intruder.

I don’t think you’ve thought through the threat model on this one, Bruce. This appears to close a gap in the protection and response that is normally hard to close — the window of opportunity, as they call it, and it does it for an accessible cost.

ThiefInTheNight June 26, 2007 5:16 AM

“We have the pronouncements of a random stranger on the Internet by the name of “ThiefInTheNight”, and then we have the testing done by a highly regarded source:

They lay out their testing protocol right before you and do it. If you have complaints with their methodology, you might wish to take it up with them. Until that happy day, I’ll accept their results over your mere assertions.

And finally, since you don’t seem to “get it”, I guess it has to be spelled out in detail. MythBusters is not “all about entertainment”. They are about core science amplified to entertainment levels.”

Love the name. Do i get a PGP key with that?
If i need to tell you why they are not proper science then I’m wasting my time.

Do you also want “proper” evidance that we landed on the moon.

In God we trust. The rest of you, show me the data! MB has no data!

Anonymous July 9, 2007 11:38 AM

False alarms causing fog deployment will generate calls to the fire department. Manpower and apparatus will be tied up on non-essential fog incidents.

Anonymous July 17, 2007 10:43 AM

These fog shield were being fiited in early 90’s in UK when the price of DRAM meant theives were breaking into companies and ripping out DRAM (and CPUs) from PC’s.

However the theives got aware (as often there were “smoke sheild” warning stickers on the premisis), they triggered the alarm and left and sat in their car round the corner. Fire brigade + owner turned up opened windows let smoke out etc and went home.

Theives returned and nicked the DRAM this time no smoke.

I can’t remember the number of salesmen/companies that approached us trying to sell us these smoke security shields. Anyway the police and firebrigade did not recommend them as they had had issues of rescuing people in real incidents where they entered into a burning building to rescue/search for people and were immediately hindered by the building being pumped full of artificial smoke, so much so they just retreated let the building burn a bit more until they could get in unhindered.

We just went for physical security of our PC’s (ie chaining to desk) and increased security of premisis rather than messing around with smoke etc.

Geektronica July 18, 2007 3:44 PM

Very interesting discussion above, though I’m not sure how we got into discussing dogs.

I’m sold on the geek factor alone, and the system looks like it would be highly effective at loss prevention when easily-grabbed valuables are at risk.

One thing that does not appear to have been pointed out in any of the above comments, including the previous one, is that FogShield’s cartridges are good for 15 shots, so the “set off and come back later” scheme would not work, as there would be plenty more smoke to deploy if a second robbery attempt were made. If I’m reading the website correctly, you get 15 shots for the $199 cartridge cost. At that rate, I’d set it off for fun when my friends came over.

I’m not sure how effective it would be to send a letter to the fire department notifying them of the system’s installation – what would they do with such information? Put a sticky note on the dispatcher’s monitor? There would still be some risk of getting your house hosed down, though if the fire department can’t tell fog from hot smoke, you probably have bigger problems to worry about. It could lead to neighbors calling the FD needlessly. I suppose the company and the system owner are covered by the letter in terms of liability, though.

Several commenters have pointed out the problem with blinding an intruder so he is trapped in your home; I agree that even with a police response this would not be desirable, since if you were home you’d have to get your family out through the fog unless you had a safe room. However, if you place the fogger (and sensors) in a smart location, it will go off while the intruder is still at the point of entry, not deep into the house. Getting out is easy – and the only logical thing to do – when the fog is driving you back the way you came, and obscuring your way further into the house. Only a poorly planned system would result in a fog deployment after the intruder had already gone down a hallway or into another room.

Thanks for the interesting debate – most fun lunch hour I’ve had all week.

Robert Briffa September 23, 2007 3:31 AM

I have seen all of the comments on these fog systems. I am a security installer myself, and having been in this job for over 16 years, I think that this system is great. It seems that the most problem that ppl are looking at, is the false alarm, which will trigger the fog for nothing. However this can be simply eliminated, by firing the machine on a 2 stage system. Most False alarms only will be triggered by a 1 stage…

bhd February 8, 2008 10:44 PM

Here’s my problem: I want to put a great big middle finger in the face of the person who thought he could enter my house, even if it’s done in absentia. If cannot rig a shotgun to my door then this is the next best thing– and that’s what’s wrong with it… for me. It’s a deterent after the fact, not before the fact. That fact is: I will still have to replace my door which costs more than replacing my TV.

I disagree that the product is silly: people are silly.

Beyond it’s super-cool, whiz-bang appeal, this product has it’s place. Yet, in most working class residences, money should be spent in better lighting and reinforcement.

You cannot stop the creation of these people: they will always be. Stop them before they break the door and you have won.

Sure, it’s not as gratifying as torturing the little twit with power tools in the basement until the police arrive, but we must learn to accept it. After all, we are civilized.

Clive Robinson February 9, 2008 12:15 PM


“tourturing the little twit with power tools in the basement”

When I was violently attacked on the street one morning in London, a friend who is seriously into diving sugested that as the perp had been positivly identified, and nothing was being done by the police we pick said individual up and pop him into a personal decompresion chamber and pump him up and down until he had the bends… admitadly as appealing as the idea was I had to decline the offer, however over seven years down the road and still suffering problems from the injuries I sustaind I am thinking did I make the wrong choice…

bhd February 10, 2008 9:53 PM

Back @ clive Robinson:
Yours is a different situation. A burglery (as I understand the term) is anonymous theft while you’re not there. The crime is sufered in terms of money, time, trust, perhaps privacy and what have you.

You speak of a different crime. It is voilent. It is in person.

Both crimes are as old as “want” and “hate”: we must stop making humans to cure them.

What’s done is done, what’s won is won, and what’s lost is lost and gone forever.

dave July 19, 2015 3:45 AM

Hey, sounds like a good plan to me, just wondering is there a toxic version available? Or maybe one with pepper spray?

Elvis Sogunro April 4, 2017 7:24 PM

I think this is a pretty good system, especially in a home like mine which is a large duplex and is quite impossible to barricade the bedrooms upstairs from the living room downstairs.

A fog enveloping the whole house will make it difficult for the burglar to move around pretty well while giving us time to call for help from inside the rooms.

My only concern here is what happens if the burglar is armed, panicked and starts shooting haphazardly?

This is good thinking. An idea I need to explore further so I can design and produce the canisters myself to make it cost effective.

One thing I’m thinking of is placing one each at every entry point into the house inside and outside e.g. the kitchen One outside triggered by an IR detector, this should slow down the burglar and if he manages to still get in, then another gets triggered again, and again as he moves through the house along with an alarm blaring right from the entry point

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