Does the electronic cigarette set off smoke detectors?

The e-cig is known for the sheer amount of vapour it produces, sometimes a far bigger cloud of “smoke” than a conventional cigarette. That leads plenty of people to wonder whether vaping indoors is likely to set off smoke detectors. Here is the answer.

A smoke detector detects… smoke

One important reminder first: the vapour given off by an electronic cigarette is made up mainly of vegetable glycerine and propylene glycol. It never contains particles produced by any form of combustion, even when the e-liquid used contains nicotine.

As its name suggests, a smoke detector is designed to go off in the presence of smoke. In practice, though, things are a little more complex, not least because there are three different kinds of detector.

The optical smoke detector

Also known as a photoelectric smoke detector, it goes off when it detects particles in the air by means of a light beam. If a large quantity of particles blocks or scatters the beam, the alarm sounds.

The ionisation smoke detector

This one has no light beam, but plates producing a weak electric current. As soon as smoke particles disturb that current, the detector sounds.

The heat detector

Rather different from the first two, this device is triggered by a rise in temperature. It therefore reacts to neither smoke nor vapour.

As you will have gathered, in theory the “smoke” from an e-cigarette cannot set off a smoke detector. But it can happen from time to time.

The rare cases where vapour sets smoke detectors off

Nothing is ever risk-free. There are indeed a few unusual conditions in which a vaper can trigger the smoke alarm, and they come down to three specific circumstances.

If you blow a large quantity of dense vapour underneath a detector, a very sensitive unit may start to sound. The closer the user stands to the detector, too, the greater the chances of setting it off. Finally, if several e-cigarette users vape in a closed, poorly ventilated space fitted with smoke detectors, the alarm may go off after a while.

In any event, while there is normally no risk in vaping near smoke detectors, optical models are more likely than the others to react to the vapour given off.