Attack of the Toxic Air Handler

There's an old saying about water, shared among health-conscious people: If you are not drinking filtered water, then you are the filter.

When you apply that proposition to the air circulating through buildings, you may think there's no problem because the air is filtered or cleaned by the building's air handler. But in many cases, that may not be true.

If a building's air handling units have a clogged, leaking or poorly draining condensate pan, this creates the perfect breeding ground for molds, fungi, bacteria and other biological contaminants that circulate continuously within the building's air and the lungs of inhabitants. And if the problem isn't solved, it likely will intensify.

Why are such air contamination problems so widespread in today's buildings and seemingly worsening?

“Since the 1970s, architects have been designing buildings that are more airtight, to help prevent energy leakage,” explains Dan Maser, president of Enviroair Consultants Inc., a provider of industrial and commercial hygiene, safety and environmental services. “And because of that, we're relying totally on the air handling system to bring fresh air into the building. But if the air handling system has a malfunctioning condensate drainage system, it can become the source of biological contamination. Moreover, that unhygienic air may continue circulating, undiluted.”

Maser, a certified industrial hygienist with over 30 years of experience in the fields of environmental, fire protection, industrial hygiene and safety compliance, knows that the likely culprit in such air contamination cases is the air handler's condensate pan or “drip pan” that is supposed to catch condensation moisture released from the air handler. It is vital that the condensate pan provide for proper water drainage. Yet, having conducted many indoor environmental air quality studies and consulting on bioaerosol cases, Maser knows that air handler condensate pans can be poorly designed or inadequately serviced.

Essentially, the molds, fungi and bacteria that plague building air systems requires only three things to propagate: the right temperature range, a source of sufficient nutrients and water. Malfunctioning condensate pans generally meet all three requirements.

“In the presence of stagnant water, the dirt that is normally present in an air handler is a food source for various biological agents, not only molds and fungi, but also strains of bacteria,” says Maser. “And because you have this continuous moisture content, you get unwanted and possibly unhealthy biological growth in the pan, which could eventually cross-contaminate the ductwork and possibly even the filters.”

Maintaining the cleanliness of the system is crucial. A key point is to reduce manual efforts required to help maintain the air quality in the building.


Obviously, the problems with air handlers made toxic by leaking, clogged or malfunctioning condensate pans go far beyond maintenance costs. In addition to that issue come several others, such as business disruption, the reputation of a “sick building,” rental of temporary HVAC equipment and potential for liability for health issues.

Maser points out that Aspergillus is one of the fungi that have been documented to cause issues in hospitals and other healthcare facilities. If Aspergillus is present in the air handling unit, it may further compromise people who are ill or elderly by exposing them to these agents when they are more susceptible to infection. [Note: This is not a reference to the transmitting of communicable diseases in healthcare facilities.]

In addition to allergic reactions and other health issues, a “sick” building caused by air handlers with stagnant water due to leaking or clogged condensate pans can make building inhabitants feel tired or lethargic.


Maser's company, Enviroair, entered an alliance with AQUIS Air Quality Innovation Solutions in order to provide recommendations to clients needing repair or replacement of air handler condensate pans in order to make their HVAC systems more healthful and reliable.

“We had seen any number of retrofit and repair ‘systems’ devised to improve condensate pan integrity and efficiency. Almost invariably they were not readily applicable to existing installations, were not strong enough or not compliant with NFPA code,” Maser says.

Maser cites the use of quick-fix membranes such as epoxy coatings, roofing membrane and roofing tar to solve condensate pan deterioration problems as being ineffectual and possibly non-compliant with building guidelines.

“In almost any case where I have seen quick-fix membranes being used for any length of time, the membranes have breached,” he explains. “Eventually water got underneath the membrane and caused it to balloon up. This not only caused a problem with biological activity under the membrane, but also led to worsening the drainage problem. Furthermore it is my understanding that these rubber membranes do not meet the NFPA guidelines for ventilation units.”

Most condensate pans are fabricated from steel, which can rust, clog and weaken when not set at the precise floor pitch. Maser says companies have found success with condensate pans that incorporate highly engineered polymers that produce no VOCs and ensure that pans remain free of standing water, rust and corrosion, and remain leak-free for greater than 10 years.

“The condensate pan is the primary source of unwanted water within the air stream of any HVAC system,” says Mike Bodon, AQUIS CEO. “We've focused on removing the water so as to eliminate a root cause of biological contamination and structural degradation.”

Ed Sullivan is a Hermosa Beach, Calif.-based writer. He has researched and written about high technologies, health care, finance and real estate for over 25 years.

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