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.
What is a face mask. Face masks are one tool utilized for preventing the spread of disease. They may also be called dental, isolation, laser, medical, procedure, or surgical masks. Face masks are loose-fitting masks that cover the nose and mouth, and have ear loops or ties or bands at the back of the head.