The COVID-19 pandemic has proven that poor air quality—especially in enclosed indoor spaces—can spread disease. While many of us would never eat at a restaurant with visibly poor sanitation practices or unclean water, hardly anyone considers how well-ventilated a place is. Indoor air quality can play a role in disease transmission for any virus spread through the air.

Indoor air quality isn’t only about disease–it can also change health outcomes by how it impacts pollution levels. Living in a home with questionable indoor air quality can lead to poorer respiratory health outcomes over time, and spending lots of time in polluted indoor air is linked with lung cancer. Here’s our guide to knowing if a building you’re in is well-ventilated, and how you can make your home safer:

Check for windows

Being inside a room with very few windows or windows that don’t open means the air has probably not had a chance to clear out. If weather permits, it’s almost always safer to have multiple windows open and a cross-breeze. Using a fan to blow outdoor air around also increases ventilation.

In some places, leaving windows open is impractical during extreme or inclement weather, such as storms or very hot or cold temperatures. . However, it only takes a few minutes a day of open windows to make a huge difference in ventilation. Even on days the weather is bad, the presence of windows in a building is a good sign. If the air smells fresh and clean and the windows are able to be opened, there is a higher chance the room is ventilated.
If you live in a very cold climate where you can’t leave your windows open, consider opening some for just ten or fifteen minutes a day to swap out the air in your house. This daily practice can help clear out viral particles and carbon dioxide, which can build up in poorly-ventilated spaces.

Trust your nose

If you can’t tell how well-ventilated a space is, you can usually trust your nose. If it smells musty, stuffy or just bad, that’s a red flag. Musty or stuffy air can mean the air contains particles that haven’t been able to disperse. If the air isn’t fresh, this often means carbon dioxide levels have also gone up, which can lead to general feelings of discomfort, tiredness and even dizziness if it’s bad enough. The issue isn’t just the lack of fresh oxygen, however—it’s also the fact that in an enclosed space without fresh air, you end up breathing air that has been in someone else’s lungs. This puts you at risk for any disease spread through the air.

Trusting your nose is also a great way to keep you safe from certain types of pollutants, including some gas leaks from old stoves and heaters. If something smells off, chances are there is something off. However, certain dangerous gases like carbon monoxide have no odor.  If you’re concerned about the ventilation in a building for any reason, having the air tested and a carbon monoxide alarm is the safest option.

Air filtration

Air cleaners and HVAC filters actually do play a role in reducing the spread of the virus that causes COVID-19. Air filtration catches particles in a machine before they reach the inside of a building, but they also remove some of the particles from the air in a building as part of a ventilation system. 

According to the EPA, to be effective at reducing coronavirus transmission, an air filter must clear particles 0.1-1 um. Certain air filters are most efficient at removing specific sizes of particles, but this doesn’t mean they can’t remove smaller ones too. For example, a filter that says “removes 99.9% of particles as small as 0.3 um” can be a good option. It likely can remove 01 um too, but not with 99.9% accuracy. Air filters for very small particles can be bought as a portable air filter, which can help keep your home safe.

Air filtration on its own is not enough to protect against COVID-19 or other viruses. For unvaccinated people, masks and social distancing along with good ventilation and a good air filter can all-together reduce the risk. In general, a strong air filtration system and an HVAC system that supports fresh, unpolluted air is the best way to maintain indoor air quality to keep you safe from viruses, carbon dioxide buildup and pollutants.