Reusable air-purifying respirators have replaceable filter cartridges. Half and Full face masks/respirators are the type commonly used to protect the user from chemical vapors, dusts and mists. Respirator cartridges can be changed with other hazard cartridge types to fit the hazard (i.e., a particulate cartridge to a gases and vapors cartridge). Some cartridges come with pre-filters to use with the respirator cartridge. Don't forget to use them. If you don't use them, you reduce the amount of protection available to you. Cartridges or respirators from one manufacturer cannot be used with cartridges/respirators from another manufacturer. Cartridge type air-purifying respirators do not protect from lack of oxygen. More info.