I have been a drug/alcohol counselor for a long time and often warn parents about household items that kids use to get high (known as inhalants). If you will read the back of the aerosol can, you will see that they are flammable because they contain propane and/or butane. I have some cans in my house that say the propellant is DME. I checked it out and that is a form of ether and it too is extremely flammable. The actual product many also contain dangerous chemicals, but it is usually the propellant that is flammable. Did you know that the propellant in whipped cream is nitrous oxide (laughing gas)?