Air Conditioner Reviews, HVAC info and Buyers Guide

Stay Clean, Stay Healthy: Bacterial Growth in Air Conditioning Systems

It’s been thirty years since an outbreak of an unknown disease caused panic in the Stratford Hotel in Philadelphia.1 The culprit? Bacterial growth in the air conditioning system. Suddenly, attention was drawn to proper cleaning and sanitation of AC systems, both commercial and residential.2 Previously, the lower temperatures in AC duct work were thought to prevent bacterial growth, but it turns out, where there is water and a food source, bacteria will grow.

Not all bacteria are harmful, but even so, cleaning your AC system will prevent the smells and possible infections from mold and bacterial growth.3

What to clean

The primary parts to focus on are where dust builds up and/or where water accumulates. In some respects, dust and water go together, as dust can absorb a certain amount of moisture and allow bacterial or mold growth.

* The filter is the easiest to clean or change – just follow manufacturer’s recommendations.
* The mats– these are the fine aluminum metal fins that look like a car radiator. They are located next to the cooling coils. You can clean these with a soft toothbrush or “fin comb” and sanitize with any anti-bacterial spray.4 Dry with a hair dryer before restarting the air conditioner.
* The inside of the case — look for any water build up and clean out any drains that are blocked. Condensation that drips from the cooling coils is common in residential AC systems. This has to be “handled” rather than prevented. Any sponge like materials in the AC housing (used to block noise) can potentially absorb this water. Make sure none are wet or getting wet. A good design won’t allow this.
* Dust will build up almost anywhere there is air flow. Use a hand held vacuum to suck all this up.
* Fan blades will require some scrubbing – the dirt accumulating here is fine and usually well stuck to the fan blade.

Special problems

Don't forget the ventilation ducts.

The coil consists of the copper tubing where refrigerant is allowed to expand and the cooling actually occurs. This presents a special problem, because water from condensation is continually produced, and cleaning won’t prevent this. For those especially worried about infectious agents, the only solution is to install UV lighting to shine directly on this area – killing any bacteria before they can get a foothold.5 Practically, this solution is best for commercial applications.

For most of us, we have to rely on the manufacturer’s design to move this water away. There are two situations where you need to clean these coils. The first is if you notice areas with dirt building up. The second is before storing a window air condition for the season (or when it won’t be operated for an extended period). A bottle brush will allow you to reach areas that are blocked by the heat exchange mat.

If you are concerned about AC efficiency, especially with older systems, please read our post on air conditioner efficiency.


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