Indoor Air Cleaning Technology

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Air cleaning technology is effective in solving a wide variety of IAQ concerns, including tobacco smoke.

Office, commercial and special purpose buildings (restaurants, daycare and wellness centers, etc.) have significant air pollution sources, other than tobacco smoke, that can cause or worsen existing health conditions. Sending smokers outside only deals with a small part of a dramatically bigger issue. It has been estimated that the concentrations of pollutants we face indoors are two to five times greater than outdoor concentrations. Sometimes it is as much as 100 times greater.

Since the typical American spends 90 percent or more of his or her time indoors, it makes sense that the indoor air quality of the office we work in, or the restaurant we go to, will affect us more than the quality of outdoor air.

Current air cleaning technology is more than sufficient to meet today's requirements for clean indoor air. Our purpose here is to take a comprehensive view of the problem, describing the most serious pollutants in both the office and public gathering place. Then, take a look at current air cleaning technologies and their effectiveness. Finally, we will provide considerations for selecting an air cleaner.

The Nature of Airborne Particulates

Particles are measured in microns. One micron is 1/25,400 of an inch. Or, better stated, there are 25,400 microns to an inch. Particles have diameters ranging from .001 to 100 microns. Those we see on furniture or floating in a ray of sunlight are approximately 50 microns or larger.

Individual particles 5 microns in size or smaller cannot be seen by the naked eye. These tend to be perpetually suspended in air and are generally referred to as "respirable." They are capable of being readily inhaled into the lungs with the tendency to stay there. Respirable particles make up 90+ percent of the total number of particles in the air that we breathe. Figure 1 compares the sizes of various types of particles and the types of air cleaning equipment that will effectively remove them.

Biological Organisms: All office environments are alive with biological organisms that the workers themselves introduce. Any group of people is accompanied by a fairly predictable array of bacteria and viruses. Besides causing the common cold, these organisms are the source of tuberculosis, staphylococcus infections, influenza and measles. Most of the diseases transmitted among co-workers can be classified as respiratory infections. It has been estimated that this category accounts for one-half of all acute health conditions.

Bacteria and viruses in office and public environments are transmitted widely by airborne dispersal. Infectious particles form free-floating "droplet nuclei" well within a respirable size range. Since people cannot be disinfected upon entering a building, there can be no effective elimination of infectious organisms at the source. The only way to do so is to treat the air to remove airborne particles.

Synthetic Materials: Buildings can create their own pollution because many building materials, textiles and furnishings create undesirable vapors, odors and fibers. Probably the biggest offender is formaldehyde, which enters the indoor atmosphere by out gassing, a process similar to evaporation except that out gassing emissions increase as indoor humidity rises. Formaldehyde is a component of foam insulation, plywood, particleboard, new furniture, ceiling and wall panels and carpets.

Airborne formaldehyde traces in offices have been found to range from 0.01 to 0.30 parts per million (ppm). Concentrations below 0.1 ppm do not cause worker problems. At 0.1 ppm, formaldehyde has a detectable pungent odor. At higher concentrations, it can cause eye burning and irritate mucous membranes