Indoor air quality testing: what to know

What the job involves, what changes the price, and what to ask a pro.

What indoor air quality testing is

Indoor air quality testing samples the air in a home for particles, humidity, mold spores, volatile organic compounds, carbon monoxide or radon, then explains what the measurements suggest. People order it when they notice odors, allergies, condensation, or after a flood, a renovation or a carbon monoxide alarm.

Signs you need it

  • A carbon monoxide alarm has gone off, or someone has headaches, dizziness or nausea that improves when they leave the house.
  • Windows fog up or condensation collects on the inside of exterior walls in winter.
  • There is a persistent musty smell, or dark staining appears on drywall, around window frames or in the basement.
  • Allergy or asthma symptoms are worse indoors than outdoors and do not clear up.
  • The house had a flood, a leak or a water event and was dried out but still smells.
  • You are buying or selling a home and want to know whether the air is tested for specific problems.

What the pro does

  • Walk the house with a moisture meter and inspect likely problem areas such as the basement, bathrooms, the attic and the HVAC equipment.
  • Set up particle counters, humidity sensors and a carbon monoxide monitor in the rooms and the mechanical space.
  • Collect air samples for mold spores or volatile compounds where the test calls for it, and send them to a lab if needed.
  • Test for radon with a dedicated monitor or a sampling device, leaving it in place for the length of the test period.
  • Check the ventilation, the combustion appliances and the exhaust fans to see how they affect the air.
  • Write up the readings, explain what each one means for the home, and list the next steps in plain words.

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Which pollutants are tested, since radon, mold, carbon monoxide and volatile compounds each need different equipment.
  • Whether lab analysis is needed, which adds time and separate fees.
  • The number of rooms and areas sampled, and whether the whole house or a single problem area is tested.
  • Whether the visit includes a visual inspection for moisture sources.
  • How long the monitoring runs, such as a short check or a longer test period.
  • Whether the job includes a follow-up test after a remedy is in place.
  • Access to the attic, crawl space and mechanical areas where samples are taken.

What a written quote should spell out

  • Each pollutant tested, and the method or instrument used for each.
  • The rooms and areas sampled, listed by location.
  • Lab fees and turnaround time, if lab analysis is included.
  • A written report with the readings and what they mean.
  • Any follow-up testing or remedy recommended, listed separately.

Questions to ask before you hire

  • Which pollutants will you test, and which instrument do you use for each one?
  • Will you test for radon, and how long will the monitor stay in place?
  • If you find mold, will you sample it and send it to a lab, or only look at it?
  • Will you check the carbon monoxide levels near the furnace, water heater and any fireplace?
  • Will you tell me the source of the moisture or the odor, or only the readings?
  • Will you give me a written report that I can share with my insurer or a buyer?
  • Do you recommend a remedy, and will you test again after it is done?

Red flags

  • The pro declares the air unhealthy from a visual look without taking any readings.
  • The pro sells a specific air cleaner before testing or naming the problem.
  • The pro cannot say which instrument was used for each pollutant.
  • The report has no readings, only general statements.

What you can do yourself

You can buy a radon test kit and a carbon monoxide alarm and place them as the instructions say, and you can look for visible water staining. If a carbon monoxide alarm sounds, leave the house and call the gas utility or emergency services from outside. Mold sampling, source tracing and any remedy belong to a qualified professional.

Licenses and permits

Indoor air quality testing is often done by independent testers or licensed contractors, and mold or asbestos remediation requires its own license in many areas. Check with your state or local licensing agency for the requirements that apply to the testing and to any remedy.

Indoor air quality testing questions

Is my house's air safe to breathe?

A test answers that for the specific pollutants measured. It cannot test everything, so ask the tester which pollutants were covered and what each reading means.

Should I test for radon?

Radon is a gas that enters homes from the ground and can build up in basements and crawl spaces. A radon test is the only way to know your level, and it is often offered along with an air quality check.

Does a musty smell always mean mold?

Not always, but a musty smell is a common sign of moisture problems. Find and fix the moisture source, then test to confirm the air has cleared.

Will an air purifier fix a bad test result?

It may help with particles, but it does not fix a moisture source, a radon entry point or a carbon monoxide source. Fix the cause first.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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