Facts about HEPA filters

1. Why were HEPA Filters developed?
HEPA filters were developed during the early days of atomic research to clean the air of radioactive particles which might escape and present a health hazard to the researchers.

2. What is a HEPA Filter made of?
The filtering material, or media, of a HEPA filter is made of very thin glass fibers. The glass fibers are made into a paper in much the same way cellulose or wood fibers are used to make paper. In thickness and texture the HEPA media is very similar to blotter paper. Air cannot get through the dense glass paper very easily so a very large area of paper must be used in the H EPA filter to permit filtering a significant volume of air. To get a large area of media into the filter it is pleated; hence the term extended surface. For example a HEPA filter, measuring 2 feet by 2 feet or 4 square feet, can have as much as 132 square feet of paper in it.

3. How does a HEPA filter work?
There are at least five means by which a HEPA filter captures particles, but the most significant of these is called "impact". As a particle tries to go through the densely packed glass fibers of the paper media, they literally run into one of the fibers and stick to it by mutual attraction. On a large scale it would be like trying to blow a grain of sand through a stack of hay.

4. Who uses HEPA filters?
Persons involved with any critical process, procedure or condition that requires contaminant free air, will use HEPA filtration to provide the clean environment needed. Some of the fields where HEPA filters are used are:

  • Micro-electronic chip manufacturing
  • Fiber Optics production
  • Analytical chemistry
  • Pharmaceutical production
  • Tissue culture laboratories
  • Space satellite assembly
  • DNA, cancer and other biological
  • research Patient isolation
  • Photographic film manufacturing
  • and processing Computer disc drive assembly
  • Atomic research
  • Orthopedic surgery

HEPA filtration is used exclusively in these applications because there is no better, practical method of obtaining the air cleanliness levels needed.

Continuous smoke removal

The air cleaner uses a powerful variable speed blower to draw the air from smoke-filled areas. As the air is drawn through the high-efficiency filter media, 99% of the tobacco smoke particles are removed on each pass. The clean air that is constantly discharged into the area is refreshing and remarkably free of tobacco smoke and other contaminants. This is particularly beneficial in lounges and restaurants, because it reduces the need for segregated smoking areas. Practically all of the dust, dirt, pollen and other contaminant particles are removed from the air passing through the air cleaner. Even the microscopic airborne particles are trapped. Everyone prefers breathing air that’s been cleaned of the many pollutants that can cause discomfort and stuffiness. Plus, lowering the pollen, spores and fungi count helps reduce the problems caused by these pollutants.

Lower heating/Cooling costs

When inside air is cleaned and recirculated, it isn’t necessary to bring in large volumes of polluted outside air that requires heating or cooling. And, it isn’t necessary to exhaust as much inside air. You save on heating and cooling costs–and save energy. However, it is important to check your local ventilation codes and comply with the minimum outside air requirements.

Extended life of furniture and furnishings

Smoke, dust and grime discolor walls and furnishings and cause excessive wear of fabrics. Because the air cleaner removes most of staining particles, there is less to settle on walls, furniture, draperies, carpets and other furnishings.

Fresher, cleaner air for customers and employees in


A far more advanced device than the "electronic air cleaner" was developed by the Atomic Energy Commission during World War II to be knows as the HEPA (High Efficiency Particulate Air) filter. Although it is completely practical to use the HEPA Filter as an economical and far more efficient replacement for the electronic air cleaner, its existence was almost unknown to the public.

The superior efficiency of the HEPA devices, plus their ability to filter without production of toxic ozone, are sufficient arguments in themselves to argue their use in lieu of the older electronic air cleaners. However, their most significant advantage appears to be their ability to filter air at very high levels of efficiency for periods of years without cleaning of complex maintenance.

Ref: An article entitled "Air For Living" as seen in Respiratory Care Magazine.