The Weller FT91000048 Standard Filter Set includes a main filter and set of pre-filters for use with the ZeroSmog Guard, Guard 2, and Guard Light Filtration Units. The main filter consists of a H13 class HEPA particle filter and gas filter with activated carbon granules. The pre-filters remove larger particles to extend the usable life of the main filter. With these filters, up to 99.95% of particles can be absorbed for ensured clean air during soldering operations.