Who here has gas masks because of train cars and their contents?
Anhydrous Amonia scares me. (I know I spelled that wrong :p)
Different HAZMAT require different personal protective gear. A gasmask it self is almost useless, with other equipment and skills.
gasmasks uses filters, the kind of filters depends on the kind of hazardous vapours, gasses, particles. The are to many kinds to practically carry and maintain for a normal citizen. Also some gasses will chew its well through filters in very short periodes of time. Thats why the emergency services carry their own air (SCBU), also to expensive, inpractical and requires lots of training and maintaince.
Most HAZMAT responce require protective gear, like suits, gloves, shoes, eye protection, hoods, etc. Not all HAZMAT suits are usefull for all HAZMAT materials. No practical to store/have/buy everything privately.
Last and not least, decontamination is a very importent skill. It tales practise to not contaminate yourself after stepping outside a protective suit.
Best skill on HAZMAT situation. Good situation awarness, knowing where the wind is heading and make sure your not down wind from a incident.