Examples from the Web for propylene
One key ingredient of the stuff: Propylene glycol, a synthetic liquid that absorbs water.
Propylene glycol is used for a variety of industrial, cosmetic, and food production uses.
The European formula for Fireball has even less: under one gram per kilogram of propylene glycol.
Propylene glycol has been used as the base for fog machine liquids and in nebulizers for decades.
The major point is that we have no studies that show the safety of propylene glycol when inhaled over the long term.
Insofar as ease of detonation is concerned, 1,2-butylene oxide has about 65 the same explosive limits as propylene oxide.
One drawback, common to both ethylene oxide and propylene oxide, is toxicity.
Tests have shown that, insofar as ease of detonation is concerned, 1,2-butylene oxide is similar to propylene 30 oxide.
Propylene oxide is less toxic than ethylene oxide but is still highly toxic.