May 03, 2020 Dirty Sock Syndrome
“Ooooh that smell / Can’t you smell that smell” – Eliminate Microbial Odors
Lynyrd Skynryd was not singing about the smell of dirty socks, but the refrain still applies, as some commercial and residential HVAC systems can smell like a high school gym locker, a phenomenon aptly named “Dirty Sock Syndrome.”
The smelly problem originates from dead, decaying microorganisms in heat pumps and HVAC cooling coils. Although different options exist for controlling these odorous occurrences, UV-C technology is the most effective and practical.
In HVAC Systems
When it comes to cooling coils, microbial buildup starts on day one. A/C components are not made in sterile environments so they arrive in your building covered with microbes (along with a small amount of lubricant.)
During the first cooling event following the initial start-up, condensate brings life to the microbes, which initially use the lubricant as a food source. Recirculated room air contains many organic materials and microbial species that aid ongoing decay and microbial proliferation.
Microbial decay (rotting) is the process by which organic substances are broken down into simpler forms of matter — including gas molecules and acids. Even the carcasses of the original organisms begin to decompose shortly after death, setting the stage for a cumulative cycle of microbial growth.
In Heat Pumps
During certain times of the year, a heat pump may warm in the morning and then provide cooling in the afternoon. This cycle can produce enough condensate to fuel microbial growth for up to 16 hours — only to release odor and toxins during the next morning’s warming routine. Heat pump coil temperatures are often not sufficient to kill the ever-increasing amount of microbes. Those that may die simply serve as a food source for continued proliferation.
Dirty Sock Solutions
Accepted methods for the complete killing of microorganisms include:
- Heat—although used in several types of food production (canning) to kill microorganisms of all kinds, it has limited application in residential systems, and it leaves carcasses behind that will serve as a future food source.
- Chlorinated compounds—chlorine (bleach), works amazingly well as it not only kills microbes, it rips up their carcasses to limit them as a potential food source. But bleach is corrosive, and requires routine application…and it stinks.
- UV-C—it kills microbes of all kinds and types and, like bleach, rips up their carcasses and other organic materials. However, UV-C produces very little heat, no odor, and leaves no secondary contamination behind — and it operates continuously, which means no build-up of microbial matter occurs, ever. UV-C is thus the most reliable and efficient means of eliminating the odor.
To cure “Dirty Sock Syndrome,” UV-C products must be installed and maintained correctly. Follow ASHRAE recommendations and locate the lamp just downstream of the cooling coil and operate it 24/7/365. Continuous operation means that even 1 microwatt of UV-C wavelength energy will add up to 2.3 million cumulative microwatt-seconds in a month’s time. That’s more than enough to kill any microbes on coil and drain pan surfaces. It’s also enough to kill and remove growth and debris already on a coil if installed as a retrofit.
UV-C will do some amazing work, but there are a few things that will help prior to its installation, where possible:
- Clear drain lines and traps.
- Correct drain line angles.
- Make sure traps are sufficient and primed.
- Seal water and air leaks.
UV-C products’ superiority cannot be denied. According to many contractors, germicidal UV-C systems are less expensive than a proper coil cleaning procedure and/or antimicrobial application. Moreover, when a coil cleaning isn’t practical, UV-C can be installed.
To read the original article that appeared in ACHR News entitled, “Dirty Sock Syndrome: What It Is, How to Prevent It,” click here
posted Apr. 28, 2015