About HEPA Filtration
- Details
HEPA filtration was first developed and used by the US Atomic Energy Commission to help protect scientists from airborne radioactive particles during the Manhattan Project. Since then it has found applications in many industries including health care, aerospace, optical, pharmaceutical, food processing and more. HEPA filters are now also commonly used in household appliances like air purifiers and vacuum cleaners. In these appliances they are used to remove the likes of tobacco smoke, dust mites, pet dander, pollen, mold spores, etc from the air. This is especially beneficial in homes with allergy or asthma sufferers.
HEPA stands for High Efficiency Particulate Air and a HEPA filter is one that meets a particular standard of air filtration. The Department of Energy in the USA defines a HEPA filter as one that can filter out 99.97% of all particles 0.3 microns in diameter or larger. In Europe there are a range of HEPA filter classes and some are less efficient (85%, 0.3 microns) than the US standard while others are more efficient (99.995%, 0.3 microns). The filters also have a maximum resistance to airflow which is often between about 250 to 325 pascals (unit for measuring pressure) at its nominal flow rate. This resistance is especially important in vacuum cleaners because if the filter resistance is too high it can affect the vacuum suction. A great website to visit to learn more about air cleaners in the home and HEPA filtration is the US Environmental Protection Agency.
While HEPA filters are quite capable at removing small particles from the air, they do not filter out odors. In the case of vacuum cleaners some will have a HEPA filter with an activated carbon insert which will enable them to remove odors from the air. Odor removal is particularly popular in vacuum cleaners designed for households with pets.
Effective filtration is also a useful feature in a vacuum cleaner because many additional allergens can be released into the air when cleaning rugs, carpets, drapes, and even bare floors. These are all areas that get disturbed when vacuuming. As a matter of fact these areas often carry many more allergens than the household air itself. HEPA filters are more commonly found on upright and canister vacuums than they are on stick vacs or handhelds, although stick vacs and handhelds with HEPA filtration are available.
Vacuum cleaner owners should be aware however that simply having a HEPA filter in your machine is no guarantee of clean air. Many manufacturers now provide a HEPA filter with their vacuums more as a means of marketing than as a means to clean the air in your home. In order for a HEPA filter to do its job all the air entering the vacuum must pass through the filter before it is exhausted from the machine. This requires that air does not pass around the filter or escape through cracks or seams in the vacuum body. Most machines are not built to these specifications but some are. Vacuums that have a sealed system are constructed in such a manner as to ensure that ALL the air entering the vacuum is passed through the filter. Marketing terminology varies regarding this specification but it is generally something along the lines of sealed system technology.
Also, some vacuum cleaner HEPA filters can be washed while others have to be replaced. It is easier to replace a filter but some filters especially HEPA filters can be expensive and will add to the cost of operating the vacuum, especially when using a bagged machine (where you also have to buy bags). Washing a HEPA filter is fairly straightforward but it should be noted that they have to be absolutely dry before placing them back in the vacuum. Air drying a HEPA filter can take quite a while and while the filter is drying you may not be able to operate your vacuum.
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