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HVAC Systems Microbe Contamination Frequently Asked Questions


Q. How does a typical home air conditioning system work?

A. A typical system functions as follows: air is drawn from the room through a return grill and passes through an air filter and into a furnace (or air handler.) Inside the air handler, which may be in the basement, garage, closet, or in the attic, is the circulating blower and a heat exchange coil commonly called the evaporator. The evaporator is cold and thus removes heat from the air that blows across it. In addition to removing heat, water also deposits on the evaporator surfaces. The cooled air returns to the room through supply ducts and outlet grills. The moisture falls into a drain pan under the evaporator and drains through a pipe out of the system.

Q. How does the air conditioning system inside a home become a source of microbial contamination?

A. The air drawn into a system contains dust, much of which is biological spores and other organic particles. Even the best filters capture only part of this material. Much of the rest falls out of the air stream onto the heat transfer surfaces. It combines with the water causing the spores to germinate and grow rapidly.

Q. Does microbial contamination in my air conditioning system impact the quality of the air in my home?

A. Yes. According to the EPA, “Contaminated central air handling systems can become breeding grounds for mold, mildew, and other sources of biological contaminants and can then distribute these contaminants through the home.”

HVAC system components can act as direct or indirect sources of particles and/or VOC gases. The greatest concern is biological growth and bioaerosol generation, most of which are potential allergens. Airborne allergens in the home are one of the hardest types of allergens to avoid. Unfortunately, heating and air conditioning systems are excellent harbors for mold, and with vents in every room this same system is an efficient distribution system.

Q. Can you prevent the growth of these biologicals?

A. Keep your system clean and treated effectively with BBJ MicroBiocideT, a broad-spectrum antimicrobial, which not only kills microorganisms (i.e., mold, mildew, fungi, and bacteria) in the HVAC system but inhibits their growth for up to 6 months. It is the only product registered with the EPA for use in air conditioning and humidifying systems.

Q. What is in it?

A. The Active Ingredient is: 2 Bromo 2 Nitropropane 1, 3 Diol, which has been used for over 20 years as a preservative in Baby Wipes, Cosmetics, and Shampoos to ensure contamination does not grow while on the shelf.

Q. My HVAC contractor says my coils need to be cleaned. What kind of coil cleaners are there?

A. Coil cleaners are generally described as acidic, caustic, or pH balanced. Acidic (or corrosive) formulas have a pH below 2. Caustic (or alkaline) formulas have a pH of 14. The chemistry of both is highly reactive to metals, especially aluminum, which most coil fins are made of.

Q. I hear caustic and corrosive cleaners are much more effective. Why not use them?

A. The problem is that the coil fins are easily etched by both low and high pH formulas. They can remove some of the metal, leaving the surface pitted. This prevents water from easily shedding off the fins. These water droplets attract microbial growth and feed it. Water droplets are then carried into the air stream and deposited downstream into the ducts, supporting secondary growth. In addition, these cleaners give off fumes that are air contaminates. Coil cleaners that fall in the category of pH Balanced will not damage the coil while cleaning or release toxic fumes.

Q. Can keeping my system clean and free from growth provide other benefits?

A. Most people believe that systems free of growth operate more economically and last longer.

Q. Why would a growth free system last longer?

A. Most corrosion in HVAC systems is caused by sulfuric acid secreted by common bacteria that chemically combines sulfur from the air with hydrogen and oxygen from water.

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