Particulate respirators use similar technology to capture contaminants now as they did years ago. There are five basic mechanisms that help capture particles (see below). All these mechanisms are used by the filter, but depend upon other factors as to which mechanism is more predominant in capturing a particular particle. These factors include particle size, breathing rates (which relates to the velocity of the particle) and humidity.
• Impaction is where a particle has a certain amount of inertia while traveling in an air steam and tends to continue on a straight path when the direction of the air stream changes and therefore runs into the filter surface rather than passing through the porous fibers.