Pack Of 2 Combination Filter Gas & Particle GreyThis combination gas and dust filter protects against organic and inorganic acid gases and vapours, sulphur dioxide, ammonia and its derivatives. Classified as a class 1 filter for gases and class 3 for particles, it can be used to protect against solvents and hydrocarbons, toxic particles and micro organisms. Equipped with a special thread for pair use only, it can be used on P410 Half Mask only.