‘Stay inside today; the pollen count is high.’ This advice means comfort and, at times, survival for many Asthma and allergy sufferers. All too often, however, staying indoors can be worse than if they had pursued their normal activities.
Is this because they have failed to adequately seal their homes and offices from the onslaught of mold, pollen and other substances that act to trigger allergic reactions? Actually the opposite may be true. The building where they are ‘hiding’ may be so well sealed that a buildup of the same and other irritants overwhelms their systems and endangers their well being.
Naturally, a sensitive individual may be at great risk when they are walking through a field of ragweed or strolling under a canopy of majestic oaks spewing pollen. At the same time, once the source of the allergy triggering particles stops producing, the normal air currents and other forces of nature quickly cleans the outdoor air to a healthy level.
In contrast, there are no natural mechanisms that reduce contamination indoors. Once a buildup of contaminates is present in an indoor environment, building systems often act to both preserve and increase the level of contamination. Modern building technology has progressed to the point where there is little unplanned movement of air between the inside and outside of the building envelope. In the past ten years, researchers have documented indoor environments that are from 10 to 70 times more contaminated than the air outside of the building. Once a contaminate such as pet dander, dust, or combustion products are released into the indoor environment, they are kept in suspension and recirculated by efficiently designed heating, ventilating, and air-conditioning systems. In addition, the conditions inside of the air handling equipment associated with these systems provide an ideal environment where mold, fungi, and bacteria flourish and add to the level of contamination.
When this fact was first recognized, many suggested that doing something to restore the air exchange level with the outside that existed with outdated construction methods might solve the problem. This approach has proven unacceptable because the comfort penalty and economic costs associated with increased air exchange are not acceptable for most people. In addition, this approach just doesn’t work. You just can’t produce enough air exchange in modern buildings to totally remove all contamination. Most enclosed buildings with a mechanical ventilating system will eventually experience air contamination unless the sources that lead to the buildup are controlled.
Air cleaning or filtration is another technique that has been advocated to prevent or minimize air contamination. Confusing claims have been made about the various air cleaning methods. There are relatively few standards so it is difficult for consumers to evaluate the various product offerings. Even where accepted test methods exist, they may be of limited value. For example, air filters are tested utilizing methods developed by The American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE). Although useful for professionals who work with filtration applications on a daily basis and therefore are experienced on how to interpret the ratings, they may only confuse a casual consumer. The ratings may not even be available at the point of purchase. ASHRAE has recently developed a new method (52-2) that provides even greater prediction of the impact of a given filter on indoor air quality. Even this new standard has more utility for selecting filtration products for commercial applications than residential use. This is because residential equipment is not designed to use most of the higher efficiency filters that are found in commercial facilities. In a commercial building, properly selected filtration is an important part of achieving good air quality.
In residences, filtration may play a less important role. This is because the design of residential equipment limits the air pressure drop across a filter that can be overcome. High efficiency filter media has so much pressure resistance, that airflow will be severely restricted if used in residential equipment. The reduced airflow will result in unsatisfactory operation and may even damage the equipment. As a result, low efficiency filtration products or electronic air cleaners are normally used in residences. Their Indoor Air Quality (IAQ) benefits are difficult to evaluate and may be limited. Extravagant claims are made for different media, devices, and designs. The existing test methods are not useful for accurately comparing or evaluating the effectiveness of low efficiency air cleaning devices. As a result, there is no way to evaluate the truth of the claims. Even where test methods can provide useful information many devices are not tested because consumers do not demand test data.
Most agree that the best way to assure acceptable indoor air quality is to control the source of contaminates that degrade the air. This is the reason clean facilities are so important and why much attention is given to such sources as paints, furnishings, and office machines. Limiting these sources is important. However, a contamination source that has been identified as major in virtually every IAQ investigation is excessive growth of bacteria, fungi, and other microorganisms.
These organisms grow to huge concentrations inside of air conditioning systems because dark moist places provide an ideal environment for growth. During active growth, most put off trace amounts of very toxic gases that might be the cause of the widely reported symptoms occupants’ report experiencing in so called ‘sick buildings’. Both live organisms and spores or other airborne allergens are released into the air stream during system operation. These can aggravate asthma and allergies and may even spread disease. Such growth is a primary source that must be controlled if IAQ is to be acceptable in any facility.
The first step in controlling such growth is to maintain the interior of the HVAC system in a clean condition. Dust and organic particles serve as food for microbial growth and the more of this soil there is in the system, the more difficult it will be to control growth. In addition, soil that is deposited on heat transfer and other surfaces in the system, greatly degrades operation of the system, shortens its useful life, and increases operating cost.
The second step is to stop the growth. Often harsh disinfectants, chlorine, and other agents are used to kill the organisms. These are not successful for two reasons: a) they are so harsh that they become a source of contamination themselves that outweighs any benefit they may have; and b) even if they kill active growth, it resumes quickly and grows to previous levels.
An agent must be selected that will kill active growth gently without adding toxic contamination to the facility and provide a long term inhibitory action that prevents or retards future growth. BBJ MicroBiocide was specifically developed to fill this primary need in HVAC systems. Using it as the heart of a preventative maintenance program is the proper way to prevent contamination rather than attempt to remove it from a contaminated facility through filtration or dilution.
Bob Baker is a member of ASHRAE and Chairman and CEO of BBJ Environmental Solutions, Inc., a manufacturing company specializing in providing clean air through environmentally responsible products.