Mace and pepper spray are allowed up to 4 oz. Aerosols less than 3 oz. are allowed. Aerosols for personal care or toiletries are allowed in limited quantities. But anything deemed flammable or a compressed gas is prohibited. Sprays for medical use are permitted. The TSO can remove any item, including those on the permitted chart.

These seemingly vague and contradictory rules are taken from the permitted and prohibited items chart. Go figure.