Half-mask respirator covers the mouth, nose and chin. The advantage is a more secure fit, and a better sealing capacity allows the respirator to be used where more toxic materials exists. The mask consists of purifying elements such as filters, chemical cartridges or canisters that can be attached directly or by use of a breathing hose, depending on the size and weight. Inhalation and exhalation valves are used to draw the air from the filter and exhale the carbon dioxide air out.