Introduction

HEPA (High Efficiency Particulate Air) filters are the highest efficiency air filters available for the filtration of small particles. Defined by the Institute of Environmental Science, a certified HEPA filter must capture a minimum of 99.97% of contaminants at 0.3 microns in size.

The first HEPA filters were developed in the 1940's by the USA Atomic Energy Commission to fullfill a top-secret need for an efficient, effective way to filter radioactive particulate contaminants. They were needed as part of the Manhattan Project, which was the development of the atomic bomb. The first HEPA air filters were very bulky compared to the HEPA air filters that are produced today. HEPA filter technology was declassified after World War II and then allowed for commercial and residential use.

HEPA air filters have been traditionally used in hospital operating and isolation rooms, pharmaceutical and computer chip manufacturing, as well as in other applications requiring "absolute" filtration.

Today HEPA air cleaners, vacuum cleaners and air filters are used in a wide variety of critical filtration applications in the nuclear, electronic, aerospace, pharmaceutical and medical fields. HEPA air cleaners, vacuum cleaners and air filters are required by law to be used in all equipment for asbestos, lead, toxic chemical and mold abatement. These HEPA filtered products must meet the strict Military Standard 282 HEPA filtration efficiency test.

HEPA filtered air cleaners, air purifiers and vacuum cleaners are highly recommended for all allergy and asthma sufferers. HEPA stands for High Efficiency Particulate Air filter. HEPA filters were developed as a part of the Manhattan Project used to remove radioactive contaminants from the air in the development of the atomic bomb. After this type of filter was declassified by the government, the Cambridge Corporation was started to market and sell this technology.

HEPA filters are usually used in two types of situations, but there are numerous other applications which will not be mentioned. One is a clean room, where the goal is to remove as much particulate from the air as possible. Clean rooms are used in the manufacturing of electrical components where a single spec of dust can ruin the entire circuit board. Computer chips, computer hard drives, motherboards, cellular phone components and a vast array of electronic components are a few examples of the type of manufacturing where HEPA filters are a must.

The second use of HEPA filters are in the healthcare industry. In these applications the goal is to have a sterile environment. A spec of dust will not do as much damage as long as it is sterile, but it easier to remove the particulate than it is to sterilize it. Also, working with hazardous items such as the AIDS virus, the TB virus, e. coli bacteria and many other deadly bacteria and viruses for the sake of research, requires HEPA filtration. Most pharmaceutical companies have vast operations requiring HEPA filtration from their research departments to their drug production line and finally their packaging departments. Some hospitals use HEPA filters over surgical tables and in their TB isolation areas.

HEPA filters are manufactured in different efficiencies from 95.0% to 99.997% depending on the need. The efficiency is determined by the amount of particles the filter will remove from the air. We have a HEPA filter which will remove 99.997% of particles the size of 0.12 microns from the air, which is actually classified as an ULPA filter. A grain of salt is between 20 and 40 microns in size, so you can see the level of filtration we are talking about. Pollen is about 10 microns in size which is barely visible to the human eye and bacteria, such as e. coli, ranges from 0.6 to 15 microns in size.

Each filter is individually tested and certified for efficiency and initial resistance by state-of-the-art testing technology; use of a penetrometer for 0.3 micron hot DOP test (DOS testing available), or dual laser spectrometer for tests at specific particle sizes. In addition, automatic scanning equipment is used to verify leak-free filters. For more stringent requirements, other methods are available. Documentation of test data is supplied on individual labels on each filter enclosing frame and a letter of certification is available for every filter.

If you are not requesting test results and certification for each of your HEPA filters, it would be wise to start doing so to make sure your supplier is up front about the quality of their products. The hardware where the HEPA filters are installed are also a crucial part of HEPA filtration as you do not want air leaking or bypassing around the HEPA filter.