HEPA filters

Know about HEPA (High Efficiency Particulate Air) filters in detail including Particles and Relative Micron Size.

Air filtration is a topic affecting everyone’s lives, whether it is for occupational safety requirements, environmental or home health concerns. Control of airborne particulates in indoor environments is critical to develop quality products, protect employees from contact with hazardous materials, or prevent health problems from prolonged exposure to allergens. How airborne particulates are controlled varies from industry to industry and from an occupational setting to a home environment. To better understand why HEPA filters are used in the biological safety cabinet industry, it is necessary to explore particle sizes, types of filters available for home and occupational use, efficiency and penetration, filter standards and performance testing.

Particles are generated or become airborne with everyday human activity. Because many people spend the majority of their time indoors at work or home, the quantity of particles floating in the air are of great concern.

For example, a sedentary person in a standing or sitting position generates approximately 100,000 particles per cubic foot. Moving from a sitting to a standing position generates 2.5 million particles per cubic foot.

Moderate activity generates 30 million particles per cubic foot. Industrial processes in manufacturing or machine shops generate billions of particles per cubic foot.

Airborne particles vary in size depending upon the source. A strand of human hair is a good reference point when considering the relative size of large and small airborne particles. Consider the following common materials nd their relative size in microns (millionths of a meter):

• Human Hair: 50-150 microns

• Household dust and lint: 0.01-100 microns

• Pollen: 10-110 microns

• Mold: 1-50 microns

• Pet dander: 0.1-10 microns

• Tobacco Smoke or Soot: 0.01-1 micron

• Viruses and Bacteria: 0.001-10 microns

Why be concerned about the size of the above particles? Solid and liquid particles smaller than 10 microns can aggravate health conditions and cause respiratory problems in humans. A healthy human body can filter out particles as small as the 35 micron size via the respiratory system however, it is exposure to smaller submicron particulate matter that can present health risks in humans.