Mold Spreads

Dear George,

Can black mold on the patio ceiling fall on my bed clothes and furniture if I had my sliding-glass door open? Can it be blown on to everything in the house by the wind, or must it be touched to contaminate my things?



Dear Patio,

The quality of outdoor air is the baseline for your house. In other words, if your house were to be tested for mold, one indicator of a problem would be if you had a higher concentration of spores inside than outside. So, generally speaking, fresh air is a GOOD thing.

But, there are always special circumstances. If you are located in a massive source of outdoor mold like in a humid location (Florida, Louisiana, etc…) after a flood or tornado, the outdoor mold concentration might be at a higher-than-normal level, thus outdoor air might not be healthy. Or, if you had an excellent air filtration system installed because you had a household member that is immunity-compromised or has asthma, it would be reasonable to expect your normal indoor spore concentration to fall below outdoor levels.

Your special situation of having mold growth at an air entry point could theoretically be the opposite of a mold filter; it is conceivable that, as you suggest, air flowing past that mold could increase the spore content of inbound air. It would probably be a good idea to give the area a sound professional cleaning prior to opening up those doors. And especially if you’re going to remediate, do it with those doors shut. When you start messing with mold-riddled areas, you’re going to stir things up, and you don’t want any stirred-up mold detritus to find its way into your living area to take root.

Make sure you also address the moisture issue. If there is moisture trapped in your patio, you need to deal with it–whether it is a leak in need of repair or trapped humidity in need of ventilation. Once that moisture is gone, and the mold is gone, you should be able to enjoy some fresh air.

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