Butane

Butane is a four-carbon alkane used alongside propane as an aerosol propellant. Its slightly higher boiling point (−1°C vs −42°C for propane) makes it useful for improving cold-weather spray performance in propellant blends. The two gases together give aerosol products consistent spray behavior across a wider temperature range than either alone. The GHS classification is H220 (extremely flammable gas) and H280 (gas under pressure) — fire hazard only, no specific inhalation toxicity beyond simple asphyxiation at very high concentrations. Not on Prop 65. Disperses as a gas immediately upon release; no aquatic pathway.