Powered Air Purifying Respirators draw air through an air purifying element with the assistance of a motor driven blower. This removes aerosols, vapors, gases, or a combination of these contaminants to provide a continuous flow of cool, clean air to the wearer. They are positive pressure respirators, which makes the work of breathing easier, and most wearers find them comfortable. The motor adds some weight to the unit, and is usually worn on a belt. As PAPRs can be equipped with a loose-fitting hood, they can be a good option for those with facial hair.
Reference:
Navy and Marine Corps Public Health Center