What is a heifer cow? A heifer is a mature female cow that has not calved, or given birth to a calf, yet. As soon as a heifer gives birth, she becomes a cow. A cow refers to a female of any age that has given birth.
When most people think about gas masks or respirators, what they usually envision is a tight-fitting plastic or rubber face mask with some sort of filter cartridge. The mask covers the nose and mouth. These are called half-mask air-purifying respirators.
The full have mask forms a seal over your nose and mouth. Because your mouth is also covered, this is the mask that is more likely to produce feelings of claustrophobia. Itâs also much bigger, bulkier, and because of the extra surface area you have to cover, is much more difficult to form a good seal.