Negative Pressure Respirator
Definition - What does Negative Pressure Respirator mean?
A negative pressure respirator is a respirator in which the air pressure inside the face piece is negative during inhalation in respect to the pressure outside. A negative pressure respirator uses mechanical filters and chemical media. Dust masks are also negative pressure respirators if they are sealed. Note, however, that inexpensive pollen dust masks available at drug stores and other loose-fitting masks are not negative pressure respirators.
Safeopedia explains Negative Pressure Respirator
A negative pressure respirator refers to any tight-fitting respirator in which the air pressure inside the face mask is negative during inhalation with respect to air pressure outside the respirator. Mechanical filter respirators are classic examples of negative pressure respirator. It retains particulate matters while the contaminated air is passing through it. These replaceable filters are basically made of wool, plastic, glass, cellulose etc.. HEPA filters are also used with negative pressure respirators and can remove about 99.97% of all airborne particulates of 0.3 micrometers diameter or greater.