In this video clip of History's Mail Call, host R. Lee Ermey takes a look at how gasmasks work and explains why those sold in surplus stores are not worth the money. Military gasmasks will save your life if they are made and worn properly. When poisonous fumes enter the mask it passes through a filter with a dense layer of carbon and thick padded air cleaner. It is then cleaned and provides fresh air to the soldier or person wearing the mask.