Should You Test Your Home for Mold? What EPA Says

In most cases, if mold is visible, testing it is unnecessary.

EPA’s guide to mold and moisture states that in most cases, if visible mold growth is present, sampling is unnecessary. It also points out that no EPA or other federal limits have been set for mold or mold spores, so a test cannot tell you whether a building complies with a federal standard — there is none to compare against.

Testing earns its cost as a check on cleanup, not as a diagnosis.

EPA notes that surface sampling may be useful to determine whether an area has been adequately cleaned or remediated. It can also have a place when a musty smell or health complaints point to hidden growth that cannot be seen — but then the investigation that matters is finding the moisture, and that usually means looking inside walls, under floors, or in the HVAC system rather than buying a kit.

Every mold problem is a moisture problem first.

EPA’s guidance is consistent that controlling moisture is how mold is controlled. Cleaning without fixing the water source means the growth comes back. Start with leaks, condensation on cold surfaces, and rooms that stay damp; the guides to finding a water leak and indoor humidity cover both.

EPA draws the line at roughly 10 square feet.

If the moldy area is less than about 10 square feet — roughly a three-by-three-foot patch — EPA says that in most cases you can handle the job yourself. With a lot of water damage, or growth covering more than 10 square feet, EPA points to its remediation guidance written for schools and commercial buildings, which it says applies to other buildings too.

Call a professional experienced with contaminated water if the damage came from sewage or other contaminated water. If you suspect the heating and cooling system is contaminated, EPA says not to run it, because it could spread mold through the building. Anyone with health concerns should talk to a health professional before starting.

Ask about the method, not only the price.

EPA advises choosing a contractor with experience cleaning up mold, checking references, and asking them to follow EPA’s remediation guidance or the guidelines of professional bodies such as ACGIH or IICRC. A contractor who wants to test visible mold before fixing the leak has the order backwards.