Healthy Indoors Magazine
Issue link: https://hi.healthyindoors.com/i/1243389
Healthy Indoors | 37 of an HVAC system that any UV lamp be shut down. Even brief exposure can cause eye damage. A MERV-16 filter destroyed by UV-C May Indoor Air Investigations LLC Filtration and Not Irradiation I once inspected a very large home with a hydro-air system and seven air handlers. Each air handler contained a UV lamp. Three of the air handlers were in a spacious, unfin- ished attic area off the second floor. The odor of ozone in that area was very strong. I asked the owners to turn off the UV lamps so I could open up the unit without worrying about exposure to the lamps. Despite the owners' substantial investments in the lamps, the filters in the air handlers were completely inade- quate. The return plenums contained exposed fibrous lining material that was full of moldy dust, and there was visible mold in all of the blower cabinets as well as on the blower blades. So much for the benefits of UV lamps! Moldy dust on blower shaft and blades May Indoor Air Investigations LLC A photocatalytic (UV-C) oxidizing unit that produced ozone. May Indoor Air Investigations LLC Since nearly all microbial contamination on coils occurs on the "front" (where incoming air impacts and the dust ac- cumulates and provides the nutrients), irradiating the front of the coil makes sense. Irradiating the back of the coil is nearly useless, because installation at this location is based on the theory that the air will be disinfected, which as noted is not the case. Proper commercial UV-C installations contain several long lamps, installed so that the entire incoming side of the coil is irradiated in such a fashion as to supply adequate energy to destroy any microorganisms on the coil; the condensate pan should also be irradiated. Can UV-C Light Cause Damage to System Components? In one mechanical system that I inspected several years ago, the UV lamp eradiated the filter and had destroyed the glue holding the fiberglass fibers together. The UV lamp was installed in front of the cooling coil but just after the filter; thus the coil and filter were both exposed by the radi- ation. The company has since included a shield on the UV lamp that prevents the filter from being eradiated. Be Careful Human exposure to UV-C can cause burns, blindness and cancer. Prolonged exposure to UV-C destroys the bonds in many organic compounds, including the DNA that provides the genetic identity of most living things; UV-C literally cooks organisms. Fortunately, the ozone layer removes nearly all of the UV-C radiation from sunlight. UV lamps in HVAC systems should never be looked at directly, so it is very important when observing the interior