You can test for formaldehyde at home with a handheld formaldehyde detector: switch it on in the room you want to check, let the reading settle, write down the number in mg/m³, and repeat in every room. Compare your readings with the World Health Organization’s indoor guideline of 0.1 mg/m³ over 30 minutes. If a room reads high, ventilate it and test again. If you need a certified result, hire a professional or use a laboratory test.
That’s the short version. The rest of this guide covers which rooms to test first, how to get a steady reading, and what to do with the numbers.
Why formaldehyde is worth checking
Formaldehyde is a colorless gas with a sharp smell at higher levels. You can’t rely on that smell, though. Reported odor thresholds range widely, from about 0.05 to 0.5 mg/m³, and two controlled studies cited by WHO put it between 0.2 and 0.4 mg/m³, above WHO’s 0.1 mg/m³ guideline. Some people notice it at lower levels than others, and noses get used to a smell quickly. Either way, a smell can’t give you a number.
EPA says the most significant sources in most homes are probably pressed-wood products made with urea-formaldehyde glue: particleboard in shelving, cabinets and furniture, hardwood plywood paneling, and medium-density fiberboard (MDF) in drawer fronts and tabletops. EPA calls MDF the highest-emitting of these. Other sources include permanent-press fabrics, some paints and coatings, cigarette smoke, and unvented gas stoves or kerosene heaters.
The numbers can differ a lot between homes. WHO reports that average levels in homes are under 0.05 mg/m³, but that concentrations above 0.2 mg/m³ show up in new or renovated buildings, around new furnishings, and during hot, humid weather. EPA reports that older homes without urea-formaldehyde foam insulation are generally well below 0.1 ppm, while homes with a lot of new pressed-wood products can go above 0.3 ppm. WHO also notes that emissions from new materials can last several months, longer when it’s warm and humid.
Your options for testing
There are two ways most people do this.
A digital formaldehyde detector gives you a reading on the spot. You can carry it from room to room, test again after you air a room out, and keep using it for months. The trade-off is that a consumer monitor gives indicative readings, not certified ones.
A laboratory test uses a sampling badge or pump that you send to a lab, or a professional who samples your air. You wait for results, and each test covers one moment in one place, but the result is validated. This is the right choice if you need documentation, for example in a dispute with a builder or landlord.
Plenty of people use both: a monitor to find the rooms that need attention, and a lab test to confirm a reading that stays high.
Step-by-step: testing with a formaldehyde detector
- Charge the monitor fully before you start, so the battery doesn’t die halfway through a room.
- Close the room’s windows and doors for a while before testing if you want to see the level under everyday conditions. Testing right after airing the room out will read low.
- Place the monitor in the middle of the room at roughly breathing height, on a table or shelf. Keep it away from open windows, fans, heating vents and direct sunlight, and don’t block the airflow around it.
- Switch it on and give the sensor time to settle, following the instructions that came with your device. Readings often move for the first few minutes.
- Write down the formaldehyde (HCHO) reading and the time. If your monitor also shows TVOC, PM2.5, temperature and humidity, note those too.
- Move to the next room and repeat.
- Test the same rooms again on a different day, and at a different time of day. One reading is a snapshot.
Temperature and humidity are worth recording because EPA’s advice for lowering formaldehyde includes keeping temperature moderate and humidity down. If a room reads higher on a hot, humid afternoon, that’s useful to know.
Which rooms to test first
Start where something is new or where people sleep.
- A nursery or child’s bedroom with a new crib, dresser or fresh paint
- Any bedroom with a new mattress or bed frame
- A home office with pressed-wood desks and shelving in a small, closed room
- The kitchen, especially if you cook on an unvented gas stove
- Rooms with new cabinets, laminate flooring or wall paneling
- Every room during your first weeks in a newly built or renovated home
What to do if a reading is high
Start with ventilation. EPA recommends increasing ventilation, particularly after bringing new sources of formaldehyde into the home. Open windows and run exhaust fans, then test again.
EPA also suggests using air conditioning and dehumidifiers to keep temperature moderate and humidity low, and choosing lower-emitting products. When you shop for new furniture or cabinets, check whether the composite wood is labeled as compliant with EPA’s TSCA Title VI formaldehyde emission standards.
If a new piece of furniture seems to be the source, let it air out in a garage or a well-ventilated room before you move it into a bedroom. Then retest and compare.
If readings stay above the guideline after ventilating, or anyone in the home has symptoms, talk to a professional. A home monitor can tell you where to look. It can’t diagnose anything.
Testing with FORMISENSE™
The FORMISENSE™ formaldehyde detector reads formaldehyde from 0.000 to 1.99 mg/m³, along with TVOC, PM1.0, PM2.5, PM10, temperature and humidity, all on one LCD screen. It’s handheld, so you can run through every room in one evening and compare the numbers. Shipping is free in the U.S.
For what the numbers mean, read our guide to safe formaldehyde levels indoors.