Living with Mold Risks

Keep an Evaporative Cooler Mold Free


Main Problems:

Swamp coolers will grow mold if not properly maintained.

Mold potentially will blow throughout the residence.

Unit may eventually leak.

Severity of Mold Risk:
Cost of Recommendation:



The Problems

Mold in Evaporative Coolers = Mold in Your Air. 

Evaporative, or swamp, coolers are commonly used for homes in warm and dry climates. They work by by saturating pads with water from a reservoir, then pulling air through the pads to take advantage of cooling from evaporation of the water on the pads. The excess water flows back to the reservoir where it is recycled, with fresh water being added to the reservoir to replace the water that evaporated. Swamp coolers can be a consistent source of mold growth, with the mold potentially being blown throughout the residence. 

The Perfect Combination for Mold Growth

Excess Water

Swamp coolers are sources of water that can result in mold growth on building materials if they leak. If not properly drained and cleaned regularly, swamp coolers can leak, damaging the roof where they are often placed. Eventually the pads and reservoir will grow mold if not properly and continuously maintained.

Organic Material

Mold thrives by consuming organic materials. Often the pads are aspen or cellulose, which will grow mold. The alternative synthetic pads will still grow mold on the dust and debris that collects on the pads. This mold is then blown throughout the home affecting your indoor air.

Increased Humidity  

Swamp coolers add humidity to homes. Although they are typically only used in arid regions with low humidity, it is possible to have localized humidity levels that exceed 60%, which would also promote mold growth. Keep the moisture level under control such as leaving another window open to reduce the overall humidity from the evaporative cooler.

Mold Prevention & Recommendations

It’s All About Maintenance

Swamp coolers take more maintenance and attention to make sure they’re operating efficiently and not harming your indoor air quality.


If it Smells Musty, Test it for Mold



Swab Test – If your house has a musty odor, don’t ignore it, as it can be an indicator of mold. Conduct a swab test anwhere you see or suspect mold in your swap cooler: the pan, pads, or ducts.  Each swab tests includes labratory analysis, and you can purchase swab tests individually or as part of the Mold Check-Up.


Maintain it Every Week


Clean every 1-2 weeks — Clean out your evaporative cooler by draining and spraying out with a hose every 1-2 weeks. Make sure you are spraying off the pads and the water reservoir.

Change pads sooner — Change the pads every 6-8 weeks or earlier if an odor is detected.

Caution: If not using the cellulose or aspen pads, the alternative synthetic fiber pads can set off chemical sensitivies from the odors coming off the polyester or melamine.


Don’t Give Mold a Chance to Grow


Purify the reservoir water weekly – Add 1 cup of 12% hydrogen peroxide to the reservoir every week to kill mold, bacteria, and yeast.

if you can

Install a bleed-off line – a bleed-off line makes sure the water reservoir is exchanged more often, reducing both dirt and biological contaminants.


Test Your Home for Hidden Mold


Every 6-12 months check your indoor air for mold growth with the Mold Check-Up. If your results show significant mold growth, that could be an indication of mold growth from your evaporative cooler or other sources or other sources. Our environmental experts can help with next steps.

Guides for tackling mold

Living With Mold Risks

Guides for reducing mold and maintaining cleaner
environments in situations we can’t change.

Flat Roof



Visible Mold


Indoor Plants


Evaporative Cooler