What is a HEPA filter?
A HEPA (High Efficiency Particle Arresting) filter can remove the smallest pollutants from the air stream flowing through the home’s air handler. These filters are rated up to 99% efficient in the removal of indoor air pollutants. They are, though, incredibly restrictive to air flow and can severely inhibit the function of your heating/cooling system if the system is not designed to handle them. Other filters, such as electronic, electrostatic, and pleated media fabric types will filter the air at various stages of efficiency that will perform very successfully for your system without extra engineering (stay between a filtration rating of MERV 6 and 12 for the best performance with the least problems). A good filter improves indoor-air quality as well as protecting the equipment. Better air means fewer respiratory ailments and allergies. Learn more from our Factsheet on Air Filters which has a complete discussion of which filter is best for your family.
A. A HEPA (High Efficiency Particulate Air) filter is a tightly woven media made from glass fibers that are pleated to maximize surface area for particle collection. HEPA filters are the most effective systems available for capturing fine particulate matter. In addition, HEPA filters maintain their performance for longer periods of time than other filters. HEPA filters remove particles as small as 0.3 microns in size (a micron = 0.00039 inches), invisible to the naked eye.
The original HEPA filter was designed in the 1940’s to retain airborne radioactive particles. Today they are widely used to clean the air by retaining bacterial and viral organisms. By preventing the spread of these organisms, it also holds true that the possibility of illness may also be significantly reduced. HEPA filters are designed to retain at least 99.97% of particulates 0.3 microns and larger. HEPA filters work in one of three ways: • Interception, where particles following a line of flow in the airstream come within one radius of a fibre and adhere to it. • Impaction, where larger particles are unable to avoid fibres by following the curving contours of the airstream and are forced to embed in one of them directly; this increases with diminishing fibre separation and higher air flow velocity. • Diffusion, an enhancing mechanism is a result of the collision with gas molecules by the smallest particles, especially those below 0.1 µm in diameter, which are thereby impeded and del
High-Efficiency Particulate Air filters (HEPA) are a type of media filter that is very tightly woven. This unique filter was initially developed during World War II to prevent discharge of airborne radioactive particles from the exhaust of nuclear reactors. HEPA filters have since become the Gold standard technology in purifying the air in industrial, medical, and military settings. HEPA filters are now the most popular choice for portable residential air cleaners. HEPA devices have a minimum particle removal efficiency of 99.97% for all particles of 0.3 micron diameter. This rating is determined using a smoke test challenge that consists of particles of 0.3 micron average diameter.
