I work in a backpacker hostel in Australia. Of course smoking is not allowed inside the building and there are smoke detectors in every room and corridor.

By law in Australia the smoke detectors in backpacker hostels set off a fire alarm which we are not permitted to turn off and the fire department is automatically notified. The entire hostel must be evacuated until they arrive and only they are permitted to turn off the alarm. Even in the middle of the night and bad weather. The charge for a false alarm is nearing $1,000.

(These regulations are specific to backpacker accommodation due to a couple of fires in which many travellers died.)

A couple of weeks ago I saw for the first time a guest "vaping" an e-cigarette. It emits a vapour that looks similar to cigarette smoke. He told me that it's fine to use these things in doors.

But I wonder, do smoke detectors specifically and only detect smoke particles? Is there zero possibility that e-cigarette vapour could ever set off a smoke detector?

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    I just did a little test, I have an e-cig and I have smoke detectors in my place, I smoked under it and the vapor does not reach it, because it is mostly water vapor and it disappears quickly. Second test was smoking directly to the detector, after 10 heavy puffs it was activated for one beep only. So, I guess smoking ecigs in rooms will not activate smoke detectors, but smoking directly to it might activate it. Aug 9 '14 at 9:59
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    I know a little about smoke detectors, and I also know that humidity can set them off (in aircrafts lavatories we see that in long flights if lavatories were not open for long times). So, by the book they can be set off by water vapor, but out of my experience in as a smoker, it never happened to me. Aug 9 '14 at 10:10

The answer is 'it depends' - on the type of smoke detector an how close the smoker is to the alarm, how much vapor is produced etc.

For the optical sensor type firealarms here is a demonstration they can be set off by vapor - while here is one that demonstrates they're not. I.e. depends on how much vapor you have and how often it is blown into the detector.

That said, it seems quite unlikely such a sensor would be triggered by vapor in normal circumstances - but as you mention in comments, sitting on top of a bunk bed, with a low ceiling may be a different matter.

More modern sensors based on ionization/CO detection should not be triggered by vapor, see here for instance.

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    To be fair I think it's also kinda hard to set off a detector with a real cigarette if you're not close to the detector. But it's possibly a bunch of people in a room could make the whole room smoky enough to do it in a way that wouldn't happen in a room full of vapers. Aug 9 '14 at 12:35
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    Although I don't smoke, I can tell from experience that the old type optical sensor smoke alarms are relatively easy to set off with cigarette smoke - two or three people smoking in a normal sized room may easily be enough.
    – greyshade
    Aug 9 '14 at 13:45

Like some others here, I was sceptical of whether electronic cigarettes could set off smoke alarms, so performed a test. The answer is yes - at least if you blow a big cloud of vapour directly into a smoke alarm (see video here!)

Modern fire alarms shouldn't be triggered by a small amount of vapour, or even cigarette smoke, but it does happen, as several friends have testified while one Reddit commenter was fined $200 after vaping in a hotel room (read the full story on Reddit here).

Particles in e-cig vapour are thought to be larger than those found in steam and are therefore more likely to set off fire alarms. In addition, it's also known that steam machines containing propylene glycol can cause fire alarms.

In short, e-cigs don't set off fire alarms often, but it possible, and it has happened.


I have smoke detectors in my camper van and vaping does set them off if I forget and blow the vapour in their direction.

In the case you mentioned I'd be very careful about vaping around yours and $1000 fine is a a bit worse than me having to hit the reset button.


Yes you can set one off. I just did it in my room. I vape in there all the time, and never had a problem before. And I wasn't blowing the vapor at the smoke detector either. I*'m not sure, but I think the detector is an optical.


I ve had two alarms set off in two different hotels while vaping (one in Panama where vaping is forbidden by a executive power decreet). But both times were with birnt puffs. So that’s the only thing you habe to be careful with I guess. I assume that a burnt puff has the same chemical composition as any burning smoke.

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