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SanAir Technologies Laboratory, Inc.

AIHA accredited environmental microbiology laboratory, specializing in testing for asbestos, mold, lead & metals, and bacteria. Free overnight shipping.

The Grave Issue of Mold Growing in Marijuana Households

When you purchase your home are you fully aware of the hidden dangers that could be lurking there? One activity that previous owners have engaged in may be prone to creating unsafe living conditions.

marijuana plant under growlightIllegally growing marijuana inside houses is nothing new. But marijuana “grow house” operations may be proliferating with some states legalizing use for medical or recreational use. A 2008 article in the Los Angeles Times discussed the increase after California passed Proposition 215, quoting law enforcement officials as estimating that as many as 1,700 of 7,500 homes in one community are growing marijuana.

When a residential home is converted to a grow house there are increased needs for electricity, water, and ventilation. Marijuana growing in houses may also be growing mold, a fungus which, although somewhat serious under normal circumstances, becomes doubly so, when found in a greenhouse, or in this case, in a house where marijuana is growing.

How Bad Is Too Bad?

Normally, when it comes to mold or mildew, the only way they affect you is if you experience an allergic reaction from inhaling the air-borne spores. The reaction might include anything from severe headaches, to skin irritation, itchiness or rash. Such symptoms are usually not as serious and can be treated by a dermatologist.

People who have asthma must be careful, however. Breathing in the mycotoxic spores will cause the asthma symptoms to increase, and those symptoms may lead of complications.

Certain strains of mold thrive exceptionally well in high humidity. And that means that the strain won’t die out when exposed to high heat. An example of this kind of strain is Anaerobic Bacteria,which if inhaled, isn’t dangerous or harmful atall, but the same bacterium when ingested, may prove to be deadly.

How Do Growers Try To Prevent Mold From Growing?

Preventing mold from growing on marijuana plants is difficult because the plants  require humidity and moisture to grow. The same is needed for mold to thrive as well. Marijuana growers employ several techniques to prevent mold from growing on the plants.

The Freezing Technique: People often store marijuana pots in refrigerators, or pass them through cold air.  That is why this technique is also called ‘fridging’. While this technique may keep the plant from contracting mold and keep it fresh longer, it is not a very good technique because there is a risk that penicillin will grow in such a situation.

The Moisture Control Technique: The major contributor to mold is moisture. That means the high moisture levels increase the chances of mold-infected marijuana.

But how much moisture is too much? And how should it be controlled? Remember: the elements that plants need to grow include humidity and moisture as well, so moisture control may be ineffective. 

Ideally, living marijuana plants require about 80 percent of water to thrive, while dried marijuana contains only 10 to 15 percent water. Any number below this will make marijuana plants brittle. Fungi and mold grows above 15 percent, which is the percentage of water content that most marijuana growers lean  towards.

How Do I Know If I Am Purchasing A Former Grow House?

With the likelihood that a former grow house can harbor hidden dangers, a buyer should be made aware of the house’s history. But obviously this will not always be the case; if the activities were illegal or hidden then there may be no disclosure.

According to the Canadian Real Estate Association and other sources, there are some signs to look for:

  • Modified ductwork that doesn’t seem to make sense.
  • Circular holes in floor joists or roof trusses from venting (look for holes that have been patched).
  • Chunks of brickwork on the exterior that have been replaced
  • Brown stains in soffits (the exposed undersurface of a roof eave) from the grow-op venting to the outside, or brand-new soffits.
  • In the winter, bald spots without snow on the roof from heat loss.
  • Stains on basement floors from pots that sat there for long periods of time, or stains in laundry tubs.
  • Modified wiring and electrical panel. Sometimes live wires can still be in the insulation.
  • New plumbing for water supply and drains.
  • Foundations and concrete walls cored or breached to get wiring around the hydro meter.
  • Warped/rotted wooden structures (staircases, floors and window cases) due to moisture damage.
  • Toxic molds form/spread poisonous spores in the open, within wall cavities, inside window frames, ventilation systems and attic spaces.

A detailed home inspection by a professional is likely to reveal issues, including those relating to moisture and mold. If mold is discovered, samples should be sent for laboratory testing so that proper mold remediation work can be done. 


SanAir Technologies Laboratory, Inc.