Healthy Indoors Magazine
Issue link: https://hi.iaq.net/i/540941
May's Ways Continued from previous page 30 July 2015 ummer is here at last, and we can look forward to some hot, sunny weather after the difficult winter we've had – at least in New England. If you haven't turned on your central air conditioning or your unit air conditioners yet, you probably will do so soon. And when you do, you may smell a "dirty sock" odor in the cooler air, or begin to cough and sneeze. Air conditioning is a welcome relief in hot weather, but it also carries with it the threat of exposure to the products of microbial growth (yeast, bacteria, and/or mold). All air conditioning units become contaminated with microbial growth for a very simple reason: whenever warm, moist air is cooled, water will form by condensation. Microbes need oxygen, moisture and dust. If components of an air con- ditioning system contain dust (and what system does not have dust??), yeast, bacteria and/or mold will grow. Return duct filled with biodegradable debris May Indoor Air Investigations LLC Bioaerosol from this microbial growth can be carried on airflows into habitable spaces, and can cause allergy, asthma, and even hypersen- sitivity pneumonitis (HP), a relatively rare but potentially life-threatening respiratory illness. How can you avoid this problem? If you have central air conditioning, it is ex- tremely important that adequate filtration be in place. Filters in air conditioning systems aren't there to "clean the air," as most HVAC techni- cians will tell you; in A/C systems, filters are there to prevent biodegradable dust from soil- ing the systems. Without adequate filtration, air conditioning coils, condensate trays and fibrous liners become soiled with dust and then be- come contaminated with microbial growth due to the dampness that is inevitably present. A mold-contaminated, dusty air-conditioning coil May Indoor Air Investigations LLC Microscopic view of brown mold hyphae growing on the above air-conditioning coil May Indoor Air Investigations LLC The typical fiberglass (furnace) filter installed in air conditioning systems is inadequate. How can such a coarse filter capture microscopic particulates, when you can see through the material? Such filters are worse than useless, because they give building occupants a false sense of security. I also don't recommend electronic filters, be- cause they are rarely maintained adequately; S