You Are What You Breathe. How to Test Your Home’s Air and Make It Safer

Air pollution can be easy to ignore from day to day, but over the past decades, researchers have accumulated a compelling list of evidence that it can pose a major threat to human health—from mental health and childhood development to heart disease. Recent events like the East Palestine, Ohio, train disaster that spilled toxic chemicals into the air in early February, have put such risks under the spotlight, causing many across America to reconsider the safety of the air they breathe.

While home is the place where many people feel safest, that may not be entirely true when it comes to air pollution. The walls that keep out the wider world can also contain a stew of dangerous toxins. There are some things you can do as an individual to protect your family from the effects of air pollution at home.

When should I consider air quality tests in my home?

In most cases, some experts recommend testing air quality if you’re concerned about specific pollutants, not to assess general air quality. In the opinion of Jeffrey Siegel, a professor of civil engineering at the University of Toronto who studies indoor air, more general home tests don’t usually justify the cost, as air shifts all the time and tests can easily be tainted. “The reason we do indoor air measurement is often to confirm a problem that we know exists, rather than to find some new problem,” he says.

If you know there’s a chance your home was exposed to a likely source of pollution—such as in the case of the East Palestine train disaster—that’s an obvious, if fairly rare, situation where broader testing of air quality makes a lot of sense. More typically, you’d want to test after you’ve found a source of contamination—for instance, if you’ve had asbestos remediation in your home, you may want to test to make sure it’s been eliminated, says Stuart Batterman, a professor of environmental health sciences at the University of Michigan. In those cases, Batterman recommends testing for specific toxins. If your home feels “stuffy or damp,” Batterman also suggests testing for CO2 levels and humidity to ensure your home is being properly ventilated.

Another toxin to be aware of is radon. The odorless gas is the leading environmental cause of any cancer according to the U.S. Centers for Disease Control and Prevention, and is responsible for some 21,000 lung cancer deaths annually in the U.S., per the Environmental Protection Agency. Radon naturally occurs in rocks and soil, and can leak into a house through any place it has contact with the ground, especially through cracks in the foundation, french drains, or sump pumps. The EPA recommends testing for radon if someone is going to spend a significant amount of time on a lower level of a home (such as if a basement is going to be used as a bedroom)—or if you are buying a new home. As the radon levels vary geographically, Siegel also recommends checking a map provided by your state or local health department to see if you live in a high radon area.

Another concern is carbon monoxide, an odorless, flammable, and poisonous gas that can leak from various places in your home, including gas stoves, space heaters, and vehicles (if they’re in an attached garage, say.) The CDC recommends having your heating systems and gas appliances serviced annually, and installing battery operated carbon monoxide detectors.

How much do air quality tests cost?

The cost of air quality tests can vary based on many factors, including the number of toxins you’re testing for, how common a test is, and the sensitivity of the test. Some tests, such as a home test for radon, can cost $10 to $30, according to HomeAdvisor. Depending on where you live, state and local health departments may even provide radon tests for free. A professional radon inspection, however, can cost as much as $800, says Home Advisor. Asbestos air quality testing, meanwhile, can cost about $287 to $585, while professional testing for volatile organic compounds like formaldehyde can cost $200 to $300 per sample.

The public may also receive free air quality testing after a disaster. Since the East Palestine disaster, the EPA told TIME it has assisted in air quality screening at 600 homes, which was paid for by Norfolk Southern, the railway company that operated the train.

Why is air quality testing so expensive?

Testing the air, especially for less common chemicals, requires three expensive things: specialized equipment, expertise, and time.

Advanced air quality testing requires hiring a specialist, and collecting samples, testing them, and analyzing the data requires a lot of labor, says John Durant, a professor of civil and environmental engineering at Tufts University. Plus, after an incident like the East Palestine disaster, the tests should be conducted multiple times for the same group of chemicals. Ideally, says Durant, samples should be collected in different parts of a home, in different weather conditions, and different seasons. In the spring, for instance, chemicals may be released as the ground becomes softer.

What do I do if I find air toxins in my home?

Once you do identify an air toxin in your home, the next step will likely depend on whether that pollutant is coming from outside or emanating from some indoor source. In the case of a disaster where there are likely pollutants in the air outside, Siegel advises sealing your home using plastic sheeting and tape, especially on lower floors and in the winter. At the very least, keep your doors and windows closed as much as you can. In the case of radon pollution, the EPA recommends sealing cracks in the foundation and installing vents and fans.

For a more high-tech solution, Siegel suggests using heating and air conditioning systems to create “positive pressure:” that means putting such systems on a setting that filters the air as it’s coming in and creates greater pressure indoors than outdoors. If such a system isn’t already installed, adding this option may be easier in more modern homes, which tend to be more air-tight, says Siegel; the first step is to ask a contractor if it’s possible.

A portable, plug-in air filtration system can also help pull particulate matter (dust or soot that comes from sources like wildfires, motor vehicles, and construction tools) out of your air “continuously and quietly,” says Durant. Some systems can be purchased or modified with filters that can absorb more contaminants for the air. For instance, activated carbon can absorb gasses.

As for indoor sources of pollution: cooking on a gas stove, spraying beauty products, or buying a new couch may seem harmless, but can add toxins to the air in your home. If you’re worried about air quality inside your home, Batterman recommends three steps: “identify the source; eliminate or control it, and use ventilation and filters as needed.”

One major polluter is combustion—the process of burning something. Cooking on a gas stove, for instance, can leak various toxins—including nitric oxide, methane, and carbon dioxide—so Durant recommends using a vent during and after cooking. Otherwise, avoid burning things inside your home, especially if someone has a breathing problem like asthma or COPD. That includes burning candles or incense. Just because something smells good doesn’t mean it’s safe—and stinky smells aren’t necessarily dangerous, says Siegel. “Odor is not a good indicator of anything,” he says. (Notably, however, gas companies add the pungent gas mercaptan to natural gas so you can smell it. If you smell gas, you should leave your home and call your gas company or 911).

Everyone should consider putting portable air filtration systems around their home, and replacing the filters regularly, says Siegel. They can be especially useful for removing particulate matter, he says, which aren’t safe at any level. “The lower we make the concentration, the safer we are,” says Siegel.

The CDC offers a wide range of resources on how to protect your family, including about lead, asbestos and other toxins. And if you’re concerned that you or a loved one is in immediate danger, the national poison hotline (1-800-222-1222) can be a helpful resource in the United States.