Before we get to the mold spore levels, there are some species you need to know about:
Penicillium/Aspergillus is the most commonly found mold species in indoor air samples. Most of the sub-species are harmless and allergenic. This group of species grows as much as the humidity in the air.
Cladosporium is the most common species of mold and is known to be allergenic. Elevated levels can be caused by housekeeping problems. It is important to take note of the room and building conditions in order to understand what may have happened.
Memnoniella is a sister mold of Stachybotrys. Both species can grow together. They are also toxic because they produce mycotoxins. The levels of mold spores in each state are different (if any regulations are set). Scientists and analysts are often unable to reach agreements. As a rule of thumb, a comparison to an outdoor sample is made. When interpreting in a laboratory, the following mold spore ranges are based on the spore/m3 value and not the raw count.
Mold Spore Levels
50-200 spores are still low. The toxic mold species Stachybotrys, Memnoniella and Memnoniella should be considered an issue.
500-1500 spores – sometimes the Penicillium/Aspergillus & Cladosporium levels are in this range and do not require remediation. These levels can be caused by normal living in an enclosed environment. Room and building conditions are also important.
1500-3000 spores are a sign of an issue, even if there isn’t an outdoor sample. Hidden mold can often be hidden behind walls in newly-flipped homes. Amplification can occur in rooms with a dusty HVAC system or in rooms that have a poor ventilation system. Additional inspection is recommended. If mold is not covered by renovations, such as a house flipped, it should be visible.
1500-3000 spores are a sign of an issue, even if there isn’t an outdoor sample. Hidden mold can often be hidden behind walls in newly-flipped homes. Amplification can occur in rooms with a dusty HVAC system or in rooms that have a poor ventilation system. Additional inspection is recommended. If mold is not covered by renovations, such as a house flipped, it should be visible.
1500-3000 spores are a sign of an issue, even if there isn’t an outdoor sample. Hidden mold can often be hidden behind walls in newly-flipped homes. Amplification can occur in rooms with a dusty HVAC system or in rooms that have a poor ventilation system. Additional inspection is recommended. If mold is not covered by renovations, such as a house flipped, it should be visible.
10,000 to 25,000 spores are normal. If there is no corresponding outdoor sample, the source of the mold spores is often identified and remediation is required. The duct system could need to be cleaned if there was no mold problem or water intrusion (including behind walls).
A mold problem can be identified easily if there are between 25,000 and 50,000+ spores. Cleaning up mold spores will be necessary and should be done by a professional mold remediator. There are approximately 11 states that have mold regulations, so it may not be possible to hire a licensed mold company in your state.
