A respirator filter is an instrument designed to remove potentially harmful or toxic substances from the air. The main purpose of any respirator filter is to clean contaminated air by removing a quantity of those pollutants via an intermediary barrier and then supply that air directly to a person. Respirator filters are commonly constructed of fibrous materials ranging from paper to foam and wool to capture large particles. In more advanced designs, a respirator filter includes an absorbent material to remove smaller particles, organic compounds, and gases. Such filters are used in applications where air quality is important, notably in medical procedures, automotive repair and construction.
Respirator filters are part of a mechanical and/or chemical process for improving air quality. Mechanical respirator filters retain particulate matter when contaminated air is passed through filter media such as paper, foam, or woven fiberglass. Chemical filters may use reactive compounds, resins, waxes or charcoal, or a combination of these materials. Filters come in a wide range of shapes and sizes to accommodate the various makes and models of respirator units. Most filters are typically for one-time use and are commonly disposable and replaceable.
Depending on the type, mechanical and chemical respirator filters remove particles and other hazards from air in one of several ways. Particles may be intercepted by coming into contact with the filter material and sticking to the media. Large particles may be unable to circumvent the media’s contours and become embedded in the media. The filter may form chemical or electrostatic bonds with the incoming particles, rendering them chemically inert or obstructing their path. The particles themselves may become a barrier for further ingress after initial filtration.
Respirator filters are more efficient at removing substances at decreased air pressures, so some filters are designed with shapes, densities and thickness to provide a larger surface area and control incoming air flow through the media. The lifespan of a respirator filter depends on various factors, such as the density of the material, the available surface area on the filter, the amount of particles or vapors in the surrounding atmosphere, humidity, and breathing rate of the person utilizing the filter. While all the aforementioned contribute to the limited lifespan of a filter, when a filter becomes too saturated with incoming particles or other obstructions and air flow diminishes or is restricted, it should be replaced.
It is important to know that respirator filters must be matched to the appropriate filtration task. Some filters are designed only for removal of large particles such as dust, while others are designed for much finer particles such as asbestos. Still others are more suitable for use involving medical procedures or industrial applications involving vapors and gases. Literature regarding procedures and safety are typically supplied with a particular filter to notify the user about its proper use.