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Unusual Mold Locations

Every investigator is aware of the less subtle hiding places for mold, like inside air conditioning units, around the standing water in the crawl space, behind the sagging drywall in the dining room, and in the mushroom garden in the basement. But, occasionally a mold analysis indicates the presence of actively growing mold and the investigator will have great difficulty locating it. This article is a short summary of some of the sneaky hiding places where mold has been found. It also addresses the situation where a mold odor exists but no mold is present. Some remediation and preventative measures are also suggested.

Refrigerator/Freezers – In refrigerator/freezers, a significant thermal gradient exists between the freezer compartment and the exterior of the unit. Where the unit is not well sealed, condensation will form on the insulation. Eventually spores will get in and mold will proliferate. This is especially true in the freezer door. Fortunately, this is the easiest location in the freezer insulation to check. Also, in frost-free freezers, there is a drain line and a drain pan under the unit. Since there is very significant air movement under the unit and the pan is near the floor where spores and dust are easily kicked up by foot traffic, the condensation pan can quickly spawn mold growth.

Replacing the door insulation, cleaning or replacing the drain line, and cleaning the evaporation pan are easy fixes; however, if the mold growth is between the compartment and the outer skin, replacement of the unit may be the only option.

Empty Beverage Cans – Since nearly everyone is into recycling, bins for empty cans are commonplace. Un-rinsed food and beverage cans (especially beer cans) quickly develop mold. Rinsing the cans or returning them more frequently is recommended.

Trash cans – From wastebaskets to trash cans, good housekeeping is cheap remediation. Everyone is aware of the kitchen wastebasket but frequently a food item discarded in the den (or, more often, a teenager’s bedroom) where the wastebasket may not be emptied for weeks can be a bigger problem. Where severe mold allergies are a problem, placing all items that could spawn mold in a separate container in the freezer until garbage day can be a good suggestion.

Potted Plants This one is rather obvious but it does need to be mentioned. Potted plants with wood chips look appealing but are especially wicked. Replacement with artificial plants is usually the best solution but not using wood chips and watering less frequently can lessen the mold growth. Watering with bleach is not a good idea (bleach kills plants).

Sump Pumps – In the summer, when pump cycling may greatly diminish or even stop, mold can begin to grow in the sump hole. To prevent re-growth after cleanup, pour about a quarter cup (less if the sump hole is small) of hydrogen peroxide in the standing water and stir it around, splashing it up a little on the sides and pipes to thoroughly wet the water line. This should be done every few weeks and an ample supply can be purchased at the local big box store.

Stand Pipes and Traps – While bacteria-saturated biomass is typically more of a problem than mold, the odor from these hiding places can be offensive. Smells like diaper pail, urine, mold, and rotten meat are all common. Remember, sewers are like life, what you get out of them depends upon what you put into them. The cleanup is very easy though. Simply pour about a quarter cup of hydrogen peroxide in the sink and around the top of the drain (or into the stand pipe). Refrain from using the sink or stand pipe for at least half an hour. Within 24 hours the problem should be gone, however, with heavy buildup, several treatments may be necessary. A monthly treatment thereafter using a tablespoon of hydrogen peroxide should prevent recurrence. While I have never seen any damage to PVC or cast iron pipes or to brass, plastic, and chrome drain rings, caution should be exercised when using this treatment.

Books – Newer books with acid-treated paper don’t seem to have a problem with mold, but older books, usually pre-1940, can have a problem. The only remediation of which I am aware is to wand the book, page by page, with UV light. Although I have never personally used this treatment and I’m not sure about how effective it is, it sounds like a laborious chore, especially if you’re doing a full set of encyclopedias or a Tolstoy novel.

Mold Outside the Walls – Occasionally, a sample analysis will detect hidden mold in a basement or crawl space where there truly is no mold present. Since this can easily turn into a “gotcha,” the first place to check is outside, around the building. Mold will proliferate if wood chips or plant debris are present, especially if the ground is damp or poorly drained or if the wood chips/debris are up against the foundation. The MVOCs from this mold can penetrate the basement wall (especially a block wall) and enter the basement.

What are MVOCs?

Microbial Volatile Organic Compounds are gases produced by mold. The musty odor which you might smell from mold is caused by MVOCs. These odors are actually chemicals which are produced by molds during some parts of the mold’s growth cycle.