In one type of mask the exhaled air is discharged through the canister, i.e., air inlet and outlet are combined. Another type is equipped with a separate outlet valve for discharging the exhaled air. The facepiece is molded to fit closely around the wearer's face so as to form a gastight seal around mouth, nose and eyes, thus ensuring that only air which has passed through the canister is inhaled. There is one type of mask, where the canister is screwed to the inlet opening located approximately at chin level. The inhaled air is purified in the canister and thus made safe to breathe.
Purification is effected by a combination of physical and chemical processes.
After a time, depending on the gas, fume or dust concentration to which the wearer has been exposed and on certain other factors, the canister becomes ineffective - i.e., the neutralizing chemicals have been consumed, or the active charcoal has become saturated or the filter pad has become clogged with dust, etc. A fresh canister must then be fitted. We hope you found the information contained on these pages informative and enjoyable. This site was created just for fun. We don't sell any of these items or know who does.