Gas masks are used to protect against inhaling harmful gases and airborne pollutants. The gas mask covers the nose and mouth with a seal, and may also cover the eyes or other sensitive soft tissues. Gas masks can also be used as respirators. Gas masks are not designed to protect the skin from any gaseous substances.
Gaseous toxic substances such as sulfur mustard or chlorine gas can be absorbed by the skin. In construction, gas masks protect against welding fumes. They are also used to prevent asbestos from being released during demolition. Gas masks can also be used in the chemical industry to handle hazardous materials such as leaking equipment repairs or clean up after spills.
Modern Israeli G.I. M-15 gas mask with filter is used by riot police and demonstrators to protect themselves against tear gas or CS gases. They are also used for their functional purpose by others. Modern Gas masks are typically made of elastic polymer in different sizes. The mask is fitted with adjustable straps that can be adjusted to ensure a snug fit.
To ensure that the gas doesn't get into the mask, it should be snug. It is preferable not to have a subtle as the gas may leak through the gaps in the subtle. When the person inhales, the mask has a filter cartridge that filters out the gaseous/contaminated air.
When the person inhales, the gas/air is drawn into the mask via the filter. The mask has a one-way port that allows exhaled air to escape if it is too pressurized. The wearer can continue to breathe until the filter(s), if any, are removed. A breathing apparatus can be used in place of filters to provide good quality air.