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.
Surgical Mask and Eye Protection. In strict sterile situations, such as in the OR or with protective isolation, the mask covers the mouth and nose. The purpose of the mask is to form a barrier to stop the transmission of pathogens. In the OR or during other sterile procedures, the mask prevents harmful microorganisms in your respiratory tract from spreading to the client. When the client has an infection, the mask protects you from his or her pathogens.