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 mask was specifically designed for compatibility with the subsystems of the AH-64, and it provides protection for the head, face, eyes and respiratory systems against field concentrations of all chemical and biological agents in liquid and aerosol forms, and against toxins and radioactive fallout particles.