Home Air Quality

Breathing clean air is a growing concern for all of us, especially in our homes. Unfortunately, simple approaches such as furnace filters and air duct filters are in general totally ineffective. They only serve to restrict the overall air movement and do nothing to capture the pollutants we want to eliminate. Even electrostatic types of furnace filters fail to remove the invisible particles. It is these particles that affect our health the most because we are not even aware that we are inhaling them all the time. They include pollens, bacteria, smoke, and a host of other allergy and asthma causing pollutants.

In hospitals, air is filtered into operating rooms with HEPA (High Efficiency Particulate Arrestors) filters. These HEPA filters are made to filter out particles as small as 0.3 microns in size. A human hair is about 50 microns thick. Particles that are 10 microns or smaller are totally invisible to us but can float around a room for hours before settling on the floor and furniture, only to become airborne again when disturbed by our, or other air movements. Being always heavier than air they will settle eventually. To capture these effectively takes very well designed equipment. The air should enter the machine as near as possible to the floor level. Usually the small air purifiers sold for homes are either too small or poorly designed to do a good job. They often claim to have true HEPA filters but fail to move all the air in the room through it. The air simply circulates within a few feet of the unit because air requires energy to move. It then takes the easiest way back to fill the vacuum created by the fan or blower. Ozone generators and ionizers all have their own shortcomings, such as unbalancing the natural make up of air and creating other hazards. Good quality HEPA filters that remove sub-micron particles, combined with enough airflow to circulate all the air in the given room, provides the best protection. To capture smells and cigarette smoke, activated carbon (several pounds, not just a sprayed on powder) must be added-and replaced every few months.

Books have been written on cleaning the air we breathe. Despite new technologies the safest approach is still with natural filters. The chart below shows the particle size of most harmful pollutants.

You can see that gas molecules are extremely small. These are the ones that carry toxins, odors, and fumes. Carbon granules that each has millions of pores to receive them can effectively adsorb them. Viruses range in size from 0.006 microns to 0.03 microns. These too, you will want to eliminate as much as possible; for example, the SARs virus. Quality HEPA filters, even if they are rated for only 1.0-micron particles, can effectively trap very tiny sub-micron virus particles each time the air passes through the filter media as the air is circulated in the room. There is an old saying in the business that "dust filters dust" and it simply means that HEPA filters become even more effective with time. But then they slowly start to get "loaded" and will require cleaning or replacement. The best HEPA filters are cleanable. The best machines are big enough and powerful enough to constantly circulate all the room air through the filters, and pick it up at floor level.

Article by Rianne Riutta, Island Clean Air Inc.
Makers of the "Duster" series of air cleaners.