A while ago the decision was made to replace all of the CFCs that were used in spray cans with another propellant because the chlorofluorocarbon gases were destroying the ozone layers. This was a good and necessary thing, but some people didn’t really think through what they were using as replacements which has resulted in some problems.
The ABC reported on one of the problems: Bathroom explosion as woman kills spider.
This isn’t the only time this has happened. A lot of the insecticides use propane as the propellant. Propane or bottled gas is heavier than air and is generally ignited by pilot lights in water heaters or ovens, but as owners of gas grills are aware, a spark is enough to light it.
I set insect bombs off in the places I’m going to rehab. I do it while the power and gas are shut off, and I don’t go in for a day afterwards. Lately I have found some foggers that don’t use flammables as propellants, and when I know they are effective I’ll mention names, but you should read the labels.