This page refers to the Swiss gas mask filter canisters that can be commonly found being sold as surplus. The canister itself contains activated charcoal with a simple cloth-based particulate filter, and as far as can be ascertained without laboratory equipment contains no dangerous components [asbestos, chromium, etc.]. These filters are however almost certainly expired, as these were produced circa 1980-1990, and even the most modern filters have a typical shelf-life of ten years. These filter canisters are hard-sealed in a OD green plastic container, which is opened by cutting through the rubber seal. Once unsealed, the filter (if not already expired, an assumption which should not be made) has an effective lifespan of perhaps eight hours in open atmosphere with no exposure to chemical agents or other vapors. This may vary if the air it is exposed to is particularly polluted, as pollutants from the air will neutralize the activated charcoal that serves as the protective part of the filter. The particulate filter, however, is likely still functional, making this filter theoretically effective against anthrax spores, and almost certainly effective against large particles such as dust and ash.