In reply to SophieEmily:
It has nothing to do with the airlines and everything to do with the rules and their application by airport security. They take their lead from the aviation authorities that set the rules - the FAA, CAA & EASA, plus any local threat analysis that change the profiling and interpretation of those rules. The rules created by the authorities are a mix of safety (compressed gases, liquids that dissolve aluminium etc) and defence against malice.
Personally, I've never understood why a cheap aerosol filled with a flammable propellant is fine, but an empty petrol stove is not. Still, they've got to find it first.