I do not think that is possible. There are materials in the filter that are effected by water or other elements, making it nearly impossible. It is better to purchase new filter(s), although some are fairly expensive.
A gas mask is used to filter out toxic agents in the air.
It uses a special filter canister that usually contains activated charcoal which absorbs all chemicals that enter the filter, leaving clean air to breathe in.
The air-filtration intake filter.
No they don't, Gas Mask filters are designed not to go bad despite if the lid is unscrewed off, unscrewing the lid of a gas mask filter doesn't have any effect on the gas mask or it's filters.
It depends on the type of mask... some consist of a (usually rubber) hood and some have just a face mask with straps to attach it. Generally it is a good idea to have short hair and be clean shaven to get the best airtight seal. As much contact with bare skin as possible should give a good seal.
at that stage it is unlikely you can preserve it.
It removes harmful chemicals from the air you are breathing.
For health reasons cleaning filters is not recommended. Check with the manufacturer of the filter to see if it is possible to clean it and how to clean it. If it is cleanable, wear protective goggles for your eyes and a filter mask to protect your eye sight and your breathing.
Store your military gas mask as follows: Use the mask faceform to prevent damage to the mask in storage. Do not store or transport the mask under heavy or sharp objects. Do not store the mask where it could be exposed to extremes Always clean and thoroughly dry the mask before storage.
Test for a gas mask tight fit as follows: With the palm of your hand, cover the filter inlet port and breathe in. The mask should collapse against your face and remain so while you hold your breath; if it does the mask is airtight.
Clean out the carburettor and jets, clean or replace the fuel filter.
The Activated charcoal inside the filter (or whatever substance it uses) absorbs the chemicals until the charcoal is completely coated.