How long do gask mask filters last?

I was curious as to how long a gas mask would last. Say if it is exposed a lot to whatever chemicals and **** and your walking through it with your mask on. How long is the filter going to last before it needs replacement, roughly?How long do gask mask filters last?
It depends on the gas, the mask and the situation.





When exposed to a nerve agent the standard MOP4 gear used by the US Army starts to break down in four hours; the filters however last longer.





In combat it is advised to change your filters once per week; at least that is what they told us in training while I was in the Army. Some gas masks have a connection for you to drink water, but only officers and infantry are usually given those masks. That means the gas mask will last until you need to drink some water and the inside of the protective gear, under all that activated charcoal is a very warm place to be. In that case the lifespan of the filters don鈥檛 matter.





Filters are pretty good, but dusty conditions like those in Iraq will shorten their life drastically. Basically the activated charcoal layer absorbs the particles in the air and you have to inhale a little harder to pull the air through that filter. As you get more particles in the filter you need to work harder to breathe. At some point it will become better to change the filter rather than keep going. Of course changing the filter in the middle of a gas contaminated area is not advised.





The efficiency of the gas mask depends on the type of gas and the amount of exposure. Fire fighters usually only carry a 20 minute air reserve and work in sealed environments to avoid inhaling smoke; their masks provide total protection.





When you wear the US Army/Marine standard gas mask the suit will break down before the filter does. But, if the gas is saran then that won't matter; saran has to be inhaled. However, if the gas is phosgene Cl2CO then it can burn through the filter. If you are a tanker then you hook your air supply into the tank's own air supply and it uses over pressure to keep gas contamination out. In that case you have access to a better set of filters.





When working with a disease like Ebola the only mask required is a simple cloth face mask which will last until it is exposed, because Ebola is a blood born illness. However, the Spanish Flu is airborne and it is 40% fatal, but once again a simple cloth air mask (like a surgeon's mask) is enough to provide protection.





If the gas is a blister agent like mustard gas then you need total coverage, any area exposed will be burned and blistered.





If the gas is Saran then you only need a gas mask, but the surgeon's gas mask is not enough. But, as a nerve agent it needs to be inhaled to work. However, weaponized anthrax can attack the body with any contact.





If you work for the CDC or a hazardous materials company then you need a strong gas mask like the one the military uses because you don't know what will come your way. However, if you go into a pure cloud of chlorine the lack of oxygen can still kill you, not to mention the chlorine can burn though the activated charcoal quicker.





I am sorry I can't be more specific with my answer, but you need to be more specific with your question like the type of mask and with exposure to what type of chemical agent.How long do gask mask filters last?
why do you need to know?