Does Air Duct Cleaning Reduce Allergens In The Home?

You see them calling to you from Yellow Pages and newspaper advertising... headlines promising to "eliminate allergy problems" and "remove dust and allergens from the home." Despite the claims and testimonials, until recently no published scientific data supported these assertions.

Of course, one of the first line therapies in the treatment of allergies and asthma is the avoidance of offending allergens. Airborne allergens in the home constitute one of the hardest types of allergens to avoid. Heating and air conditioning systems have been established as harbors for molds, and certainly with vents in every room this same system is an efficient distribution system. So certainly the "sanitation" of this system is of great interest to allergic and asthmatic patients.

To test the theory that commercial air duct sanitation is effective in reducing indoor allergen levels, eight residential "heat-ventilation-air conditioning" (HVAC) systems in six homes during winter (heating mode); and six HVAC systems in five homes during summer (cooling mode); were sampled to measure fungal "colony forming units" (CFUs). The sampling was done before and after HVAC sanitation occurred. Two homes in which no duct cleaning was done served as controls in each phase of this study. The homes ranged in size from 1,500 sq. ft. up to 4,600 sq. ft., and all were of brick or brick and wood frame construction. The study took place in north Texas.

Sampling was performed using culture plates of malt extract, which provides an excellent growth medium for fungal colonies. The plates were placed directly in the air stream.

The baseline CFUs were found to be approximately equal in the control and study homes. Eight weeks after the sanitation procedure, the study houses exhibited a whopping 92% decrease in CFUs during the winter, and an 84% reduction in the summer. Over the same 8 week period no reduction in CFUs was observed in the control houses.

This indicates dramatically that air duct cleaning by a qualfied commercial firm does indeed provide relief from airborne molds, one of the most common aeroallergens. This benefit can be extended by installing a high efficiency intake filter following such air duct cleaning.

Another interesting fact the researchers noted was that pre-cleaning CFU levels were much higher in the summer than in the winter. They speculate that this could be due to the fact that in a cooling mode, there is higher moisture content due to the evaporative coils.