When should you test for mold?

Match the test to the question

A test is worth doing when it answers something you need to know. The situation usually decides which question that is.

Situation	The question a test answers	Test that usually fits
Musty odor, nothing visible	Is something growing, and where?	Inspection with air or wall cavity samples
Leak or flood that took a while to dry	Did mold follow, and has it spread?	Moisture mapping plus air samples
A doctor asked about the home	Has this home had a water-damage mold problem?	ERMI or HERTSMI-2, sometimes a mycotoxin panel
Buying, selling or renting	What is the condition, on paper?	Inspection with air and surface samples
Remediation just finished	Did the work succeed?	Clearance testing
Insurance, landlord or legal matter	Can we document it?	Inspection with a written report and lab data

Getting the timing right

When you test changes what the result means. A few rules of thumb:

• After a leak, fix and dry first. The EPA advises drying wet materials within 24 to 48 hours to prevent mold growth. If materials stayed wet longer than that, test once the water is stopped, so the results reflect the damage and not an ongoing flood.
• Before remediation, get a baseline. Pre-work samples give the clearance test something to be measured against.
• After remediation, test before containment comes down. That’s when a failed area can still be cleaned again without spreading anything. See mold clearance testing.
• Before moving in, not after. Testing an empty home is simpler than testing one full of furniture and belongings that may need cleaning too.
• Retest over time if someone is sensitive. A dust test months after the work shows whether the home is staying clean.

When testing can wait, or isn’t needed

• A small patch of visible mold on a bathroom ceiling or window frame. The cause is usually plain, and the fix is cleaning plus ventilation. More in do I need a mold test if I can see mold?
• An active leak that hasn’t been repaired. Testing now measures a moving target.
• A house that was just deep-cleaned, painted or recarpeted, if the plan is a dust test. The dust history that ERMI and HERTSMI-2 rely on has been wiped away.
• No odor, no water history, no symptoms and no staining. Testing a dry, healthy house mostly confirms what you already know.

Signs that mean it’s time

The most common reasons people call us are a smell that won’t go away, a stain that keeps coming back after painting, humidity that stays above 60 percent in a basement, or a history of water in a part of the house nobody looks at. Any one of these is worth a look. Two together are a good reason to book. If you’re weighing whether hidden growth is possible at all, read can you have mold without seeing it?

How to prepare so the test is worth it

Keep windows and exterior doors closed and run heating or cooling normally for the day before an air test. Skip vacuuming and dusting before a dust test. Write down what you know about leaks, repairs and when any symptoms started, because that history tells an inspector where to look first.

We test and remediate buildings. We don’t diagnose or treat medical conditions, and a home test result isn’t a medical diagnosis. If you have symptoms, please work with a doctor. With your permission, we’re glad to share test results with them.