What exactly is a HEPA filter? Where should the filter be located? And, can HEPA filtration levels be achieved without using a HEPA filter? John Taylor clears the air on some commonly asked questions.
We recently had an enquiry from a school following a parent’s request for the school to assist with a medical problem their child was suffering. The child was severely affected by dust mites with an allergic reaction that was almost off the scale.
The parents were trying a number of chemical concoctions at home and were asking the school to follow their home procedures, however, the products they were using could cause allergic reactions to the other children in the class.
We enlisted the help of a specialist cleaner with expertise in dealing with allergens and recommended a basic procedure of vacuuming with a vacuum cleaner fitted with a HEPA filter.
The reason we suggested using a HEPA filter was that commercial vacuums with HEPA filters capture 99.97 per cent of dust particles down to 0.3 microns (human hair is approximately 30 microns, one micron = one millionth of a metre). The size of a dust mite is approximately 20 microns.
The vacuum cleaner would not only pick up the dust mites it would also capture them and prevent further distribution. A vacuum cleaner without adequate filtration can be one of the best distributors of dust and other contaminants.
What is a HEPA filter?
HEPA is an acronym for High Efficiency Particulate Air and has become a generic term for highly efficient filters. It works by forcing air through a fine mesh that traps harmful particles.
According to The Vacuum: A History by Carroll Gantz: “The original HEPA filter was designed in the 1940s and used in the Manhattan Project to prevent the spread of air-borne radioactive contaminants. They were introduced to the commercial market in the 1950s under a registered trade mark. It is the best known filter for removing at least 99.97 per cent of particles from air, such as dust, animal dander, smoke, mould, and other allergens that are 0.3 microns or larger, thus improving air quality.”
While it is widely accepted that HEPA filtration refers to filtering 99.97 per cent of particles at greater than three microns there are different international standards. The most widely used seems to be the European Standard EN1822:2010. This states that there are three filtration classifications:
- EPA 10 – EPA 12: Efficiency Particulate Air Filter
- HEPA 13 – HEPA 14: High Efficiency Particulate Air Filter
- ULPA 15 – ULPA 17: Ultra Low Penetration Air Filters
And just to add to the confusion, a “HEPA Type filter” is capable of capturing 99 per cent of particles that are two microns or larger. There is a company that manufactures filters in California, USA called HEPA Corporation. We tend to accept that HEPA filters are classified as H13 or H14.