Derek ColeGM, Simmons One Hour Heating & Air · AI HVAC Answers

Prevent Moldy Smells in HVAC: The Impact of Drain Lines and UV Technology #shorts

26 Aug 2026 · 1 min

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In this short video, Derek Cole explains why HVAC systems can develop a damp, musty, or moldy odor. He describes how hot air passing over cold coils creates condensation that drips into a drain pan. If the drain pan does not drain properly, the standing water creates a dark, damp environment where microbial "growth" thrives, producing the unpleasant smell the first time the system is turned on. To stop this, he recommends introducing ultraviolet (UV) light into the HVAC system to inhibit microbial growth in the drain line and pan.

Chapters

So the byproduct of that is water. So that's why you have drain lines. That's why you see water dripping outside. So what will happen is when you have that hot air going across that cold coil, you get condensation and that's going to drip down to the drain pan. Well, if that drain pan is not draining or something is the matter, things will start growing in that drain pan because you have cold water Sitting in a damp, dark spot. So the thing that happens is growth, right? There's like all kinds of mold, so we don't call it mold, we call it growth. So you start getting— the first time you turn on your heat or your air conditioning, especially, you get that kind of damp, musty, moldy kind of smell. So the way to prevent that from happening is to introduce UV into that system somehow.