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.
bag mask device. A manually operated resuscitator used to ventilate a nonbreathing patient or assist the ventilation of a patient who is not breathing at an effective rate or tidal volume. The device consists of a bag, an oxygen reservoir system, a one-way flow valve, and a clear face mask.