An important question about formaldehyde is how long it takes for formaldehyde to off-gas in new homes and new furniture–how long will it take for levels to get back to normal? The best data I’ve seen suggests formaldehyde takes about two years to off-gas back to normal levels.

What is Formaldehyde?

Formaldehyde is a colorless and strong-smelling gas. You can often smell it in new furniture and homes. Exposure to formaldehyde can occur through inhalation of the gas or absorption through the skin. It has been classified as a human carcinogen by some health organizations when exposure levels are high.

Why We Need Real-World Tests on Formaldehyde

When researching this question, I wanted to see tests in real-world apartments. I want to understand how formaldehyde acts in real homes, not in a laboratory plexiglass container. That’s critical because sometimes people take results from sealed boxes and incorrectly apply them to our homes.

For example, many articles trumpet how great plants are as purifiers. Plants do work in sealed test containers surrounded by grow lights, but real-world tests show that plants have no detectable effect on particulate pollution (1) indoors (including tests I did in Beijing). So it’s important to have real-world data.

Real-Home Formaldehyde Off-Gassing Tests

Fortunately, scientists in Hong Kong did real-world tests. They tested for formaldehyde and other VOCs in homes and then compared new/remodeled homes with older apartments. The data showed formaldehyde fell 48% one year after remodeling.

After two years, formaldehyde dropped to the same levels as in older homes. 

Off-Gassing Formaldehyde From Homes – Caveats

But it’s worth noting that these are home in Hong Kong. Why’s that important? Because temperature and humidity make formaldehyde off-gas faster. In cooler, drier places like Beijing or New York, this off-gassing will probably take longer.

Read More:

3 Things You Need to Know About Formaldehyde

Part 1: Why formaldehyde testers are fake (and why it’s actually scientific to just use your nose)

Part 2: How long it takes for formaldehyde to off-gas from new and remodeled homes

Part 3: Three data-backed ways to reduce formaldehyde and other VOCs in your home

BONUS: Want Smart Air Professionals to Help You?

Smart Air can help you with formaldehyde removal and air quality testing. Smart Air is a certified B Corp started by University of Chicago Professor Thomas Talhelm to combat the myths big companies use to inflate the price of clean air.