I intend to travel through rougher foreign parts on the cheap. To protect me from being robbed or raped I am going to buy a gas alarm. What do I need to know when buying one? What gases should it detect and at what thresholds? Why do only independent online stores from Europe sell them? Should I get an LPG gas detector too? Do models that run on small battery power exist?

Edit; I am not asking whether I should be worried. Please provide help on shopping for the alarm.

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    The odds of this are so small, that if you're going to protect yourself against this, you'll also want to avoid taking cars and buses, walking through shops, and talking to anyone in case they're dangerous. I know you're asking and it's a valid question and I've upvoted it, but seriously, don't worry about it.
    – Mark Mayo
    Commented Apr 3, 2014 at 1:23
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    I suppose this could be an actual technique used by actual criminals, but it sounds even more like the kind of legend that might be propagated by clueless emails and sellers of "detectors" that are just empty boxes with blinky lights. This might be a better question for Skeptics.SE, if you can find a notable claim that this is a serious problem. Commented Apr 3, 2014 at 1:27
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    Just because they were stealing NO2 doesn't mean they were using it for robberies; nitrous oxide is also a fairly popular recreational drug. Commented Apr 3, 2014 at 3:12
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    Em... Why is this question on-topic on a travel site?
    – sharptooth
    Commented Apr 3, 2014 at 7:24
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    Just a correction: Laughing gas / nitrous oxide is N2O, not NO2 Commented Apr 5, 2014 at 0:26

4 Answers 4


Seriously, this is not a problem.

Why ? The brother of my former girlfriend was an anesthesiologist. I was interested if it is possible to have something for sleeping (I am seasick) and I got a longer speech about anesthetics. Concerning gases: If you are not an expert, trying to gas someone does either nothing, alert you immediately or kill you.

Mind you, this were experts:


and it killed more hostages than bullets and it did not knock out all terrorists.
Robbers do not gas someone, they are relying on brute force (smashing the door). Thieves are not stupid enough to risk killing the victim. Buying a gas detector is lost money. And really, do you expect that criminals carry along flasks of sleeping gas which are not even guaranteed to work ?

This does not mean that criminals cannot knock out victims, but they are either spiking your food with drugs or using needles, in both cases they need contact to you or to your food. The chloroform or ether rag from the "damsel in distress" movies are mostly fiction, too. They may work, but they are dangerous (killing you) and unpredictable (suffocation, not working at all). Another option is tasering.

If criminals do not use violence, they simply rely on stealthiness. Once inside, they plunder noiselessly and if they are afraid that you wake up, they are now in vicinity if they are really intend to knock you out.

EDIT: More info in this thread: I also recommend the calculations how much gas of different sorts are needed to flood a room on page two.

Royal College of Anaesthetists

Despite the increasing numbers of reports of people being gassed in motor-homes or commercial trucks in France, and the warning put out by the Foreign Office for travellers to be aware of this danger, this College remains of the view that this is a myth. It is the view of the College that it would not be possible to render someone unconscious by blowing ether, chloroform or any of the currently used volatile anaesthetic agents, through the window of a motor-home without their knowledge, even if they were sleeping at the time. Ether is an extremely pungent agent and a relatively weak anaesthetic by modern standards and has a very irritant affect on the air passages, causing coughing and sometimes vomiting. It takes some time to reach unconsciousness, even if given by direct application to the face on a cloth, and the concentration needed by some sort of spray administered directly into a room would be enormous. The smell hangs around for days and would be obvious to anyone the next day. Even the more powerful modern volatile agents would need to be delivered in tankerloads of carrier gas by a large compressor. Potential agents, such as the one used by the Russians in the Moscow siege are few in number and difficult to obtain. Moreover, these drugs would be too expensive for the average thief to use. The other important point to remember is that general anaesthetics are potentially very dangerous, which is why they are only administered in the UK by doctors who have undergone many years of postgraduate training in the subject and who remain with the unconscious patient throughout the anaesthetic. Unsupervised patients are likely to die from obstruction of the airway by their tongues falling back. In the Moscow seige approximately 20% of the people died, many probably from airway obstruction directly related to the agent used. If there was a totally safe, odourless, potent, cheap anaesthetic agent available to thieves for this purpose it is likely the medical profession would know about it and be investigating its use in anaesthetic practice.

ADDITION: The portable gas alarms are not intended for narcotic gases, but should warn the user of toxic fumes endangering your air passages (caused by combustion like a fire with burning plastic e.g. hydrogen cyanide, hydrogen chloride/fluoride), choking gases (carbon dioxide, carbon monoxide) and explosive mixtures (Butane, propane).

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    I guess this is why almost all the alarms are intended to protect someone who is sleeping.
    – ran8
    Commented Apr 4, 2014 at 19:58
  • @ran8 I added the reason: Yes, they protect someone who is sleeping, but not against narcotics, but toxic/choking/explosive gases. Commented Apr 5, 2014 at 0:34
  • Some specifically note ether.
    – ran8
    Commented Apr 5, 2014 at 16:33
  • Yes, because ether is highly flammable and if vaporized in enough quantities even explosive. Commented Apr 5, 2014 at 22:00
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    Sigh. No, but ether is used in "Startpilot(e)", used in RVs if the motor needs starting. Anyway, look up all possible narcotic gases, then get your gas detector. As all gases are heavier than air, you put your detector on the ground and you sleep as high as possible. Once the detector started, you grab your scuba gear (which shall be a nice hobby, by the way), put the nose clamp on and now you are protected. As you cannot scream because you need to bite the mouthpiece, buy one of those loud pocket alarms and/or a legal weapon. Now you have done everything possible to be prepared. Commented Apr 7, 2014 at 0:00

The reason you're finding that they only have them in Europe is gassing is not a common problem in other parts of the world. (Honestly, it's not that common in Europe either). In most dodgy parts of the world, criminals will force their way in, jimmy the locks, or just wait outside your door. Slip something in your drink, or even just blow scopolamine in your face (the last one terrifies me). You can worry about these things, or not. But traveling is very similar to investing, know your risk going in and determine your maximum loss.

With that said, the string of gassings appear to be in rich resort towns, targeting villas, etc. They appear to pick the places by targeting expensive rental cars, located in front of nice rental houses. If you're going budget, you likely won't encounter these things.

Still not convinced? Grab the gas detector. Sometimes peace of mind is worth a couple hundred bucks. But the gas detectors are tricky, since they detect different gasses, and you need to predict what type of gas they might use. Most common in the EU is Nitrous Oxide, and most detectors being sold are meant to work inline, and are not effective at detecting ambient levels like a smoke detector. By the time it detects ambient levels, you'll likely be knocked out with the alarm going off, and what good is an alarm if you can't move?

But once again, these things are extremely rare. I'm on the road almost 40 weeks a year and have never come across this. Most of my friends living in dodgy parts of the world (Somalia and Cambodia come to mind), have been robbed. But it's always blunt gun or knife point. All you can do is act smart, don't flaunt your money, and make safe and reasonable decisions.

All the best and have a safe trip, the world is much scarier before you experience it.

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    +1 for being terrified of scopolamine. Holy crap. (Also for not being terrified in general despite stuff like this being out there.) Commented Apr 3, 2014 at 4:27
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    "Most common in the EU is Nitrous Oxide" or, rather, "Least vanishingly rare..." Commented Apr 3, 2014 at 9:17
  • common enough in Europe to warrant having detectors? Lived in Europe all my life, never once heard of anything like that except a single rumour about Russian gangsters using it on overnight trains in Russia to knock out entire cars by pumping poison gas into the air vents and killing all the passengers and crew so they can steal their belongings. And THAT I've never heard of actually happening in reputable sources, only hinted at.
    – jwenting
    Commented Apr 4, 2014 at 8:20
  • @jwenting Maybe try hearing things from non-fiction sources? Here's one incident. dailymail.co.uk/news/article-1302917/… Commented Apr 5, 2014 at 1:33
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    @StephenP. Non-fiction ? Daily Mail is the British equivalent of the National Enquirer. Commented Apr 5, 2014 at 22:03

Quite apart from the other answers, what would you even do if your detector goes off?
Are you also going to carry a gas mask and full protective gear (gas can affect you through the skin, at least some of them) and are you trained to put it on under stress quick enough to be effective (likely seconds)?
And then, if a group of criminals were expert enough, determined enough, and resource rich enough to have access to sleeping agents and the means to disperse them AND knew how to use them, do you really think they'd not have other means to subdue those who fail to be knocked out by that gas?
Things like knives, silenced guns, clubs, lethal injections? Things that will surely kill you because now you've actually seen them and could be a witness against them...

It not only just doesn't happen so there's no need to worry about it happening, it also were it to happen would only make matters worse for yourself if you didn't succumb to the gas.

  • The alarm is enough; hopefully it would wake my neighbors.
    – ran8
    Commented Apr 4, 2014 at 15:58

You are right to be worried. Here's an article in a popular British Newspaper: http://www.dailymail.co.uk/news/article-1302917/Gassed-beds-Riviera-robbers-Terrifying-ordeal-British-tourists-falling-victim-Mediterranean-gang-crimewave.html It is in fact very common. The gas they use is nitrous oxide and contrary to what a previous poster has said, there are alarms which detect such gasses as these alarms are available to dentists to prevent accidents from leaks. I have been gassed on an overnight train going through France and a couple which I am friends with were gassed in their caravan in France. They slept on top of their money and the criminals actually moved their bodies to get to it. They took everything including clothes. It's really not nice to dismiss these reports as myths when you people really have no idea what is going on out there. Where I live in Scandinavia one of the biggest retailers actually sells narcotic gas alarms. How effective they are I can't say but I don't think I would be relying on that alone if I was worried. And to the poster who said what would you do if someone did come in and you were awake as though there is nothing you can do..... You can call the police for a start. I know someone who hunts deer and camps in a caravan. He has a narcotic alarm so I don't think much good would happen to anyone who decided to gas his caravan.

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    "British Newspaper" and "Daily Mail" in the same sentence? I'm tempted to downvote you just for that. Commented Aug 9, 2015 at 22:14
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    To echo @BurhanKhalid the Daily Mail is notorious for running sensationalistic stories, warning of the dangers of just about anything. Commented Aug 9, 2015 at 22:40
  • Well, this doesn't answer the question, which is how to select an alarm. So -1.
    – Flimzy
    Commented Nov 28, 2015 at 13:39

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