How to improve indoor air quality at home

Español – Spanish

With mask mandates lifted, you might have recently seen more emphasis on proper ventilation inside businesses to help prevent the spread of coronavirus.

However, it's not just businesses that need to worry about ventilation. Did you know that the average person spends 90% of their time indoors? That makes us vulnerable to indoor air contaminants — including, but not limited to, COVID-19.

Whether it's to protect you from spring allergies, wildfire smoke season or illnesses like COVID, it's good to know what to do to improve your indoor air quality. Here are some easy tips to follow.

Download and share these slides with your community.

Slides are available in the following languages: አማርኛ (Amharic), العربية (Arabic), 简体字 (Chinese – Simplified), 繁體字 (Chinese – Traditional), دری (Dari), English, 日本語 (Japanese), 한국어 (Korean), Kajin M̧ajeļ (Marshallese), ਪੰਜਾਬੀ (Punjabi), Русский (Russian), Af Soomaali (Somali), Español (Spanish), Wikang Tagalog/Filipino (Tagalog/Filipino), ትግርኛ (Tigrinya), Українська (Ukrainian), Tiếng Việt (Vietnamese)

You’ve probably heard that outdoor air can become polluted and unhealthy due to things like vehicle emissions from traffic, exhaust from factories and wildfire smoke. However, indoor air can sometimes be even more polluted than outside air.

This can be due to the materials we use to build homes – like paint, sealants, flooring, and insulation – as well as the items we keep inside, like electronics, appliances, toys, furniture, carpets, and air fresheners. Indoor air can also become polluted from common indoor activities, like cooking that gives off fumes and cleaning with chemicals. Dust is also a big contributor to poor indoor air quality. Chemicals can stick to small dust particles that we then breathe in, making them more dangerous to our health.

Poor indoor air quality has both short- and long-term outcomes. In the short term, it can cause irritation of your eyes, nose and throat, headaches, dizziness and fatigue. In the long term, it has been linked to asthma and other respiratory diseases, worse student performance, decreased cognitive function and increased risk for chronic diseases.

People most sensitive to poor indoor air are young children, pregnant women, and older adults age 65 and up. People with certain conditions like respiratory illness, heart disease, kidney disease or other chronic diseases, as well as people who have or have had COVID-19, may also be more vulnerable. If you have any of these folks in your household, it's extra important to see what you can do to improve air quality for them.

Steps you can take fall into three categories:

Prevention: Preventing particles from being in the air in the first place.

Ventilation: Increasing air flow to dilute the number of harmful particles in the air.

Filtration: Filtering the air to remove particles.

If you are sick, gather with visitors outdoors when possible or consider wearing a mask indoors if you must be around others to help prevent spreading illness. Masks can block up to 70% of droplets coming from mouths and noses. The best thing you can do, however, is not invite other people into your home who are outside of your household when you are sick, and not have people over who are sick or experiencing symptoms.

Other steps to take to avoid introducing pollutants into your home:

Ventilation is bringing in fresh air from outside to improve air circulation and dilute the number of harmful particles in your home. Opening windows is great idea if the weather allows. You can also place fans in a window to blow potentially contaminated air out and pull new air in. Unfortunately, this is not a good option for communities living next to major roads or industrial activities, because the outside air may already be polluted. You should also avoid opening windows during wildfire smoke events.

Use whatever mechanical ventilation you have available in your home: run an exhaust fan over the stovetop when you’re cooking, and make sure the exhaust fan is on in the bathroom when taking a shower. Check if your vent actually vents to the outside: many unfortunately just vent indoors, recirculating the bad air inside. If this is the case, opening a window can help.

Consider buying a portable air cleaner with a HEPA filter, which captures and removes tiny particles from air such as pollen, smoke, germs, mold and dust. Air cleaners vary widely in price, but some units costing around $100 can effectively clean a room.

For a more affordable DIY option, you can easily make a box fan filter at home for around $35 that can reduce certain types of air pollution by 90%. Learn more about how to make a DIY filter fan in this blog post or by watching the video below:

You can also build an even more effective filter – known as a Corsi-Rosenthal Box – at home with a box fan and four 20″ by 20″ filters, as seen in the video below:

Use a portable air cleaner or box fan filter during wildfire smoke days, when the air outside is poor, and during or after indoor activities that might impact your air quality. It's a good idea to place the filter where people spend the most time, or in areas where you can't open windows and doors or can't turn on an exhaust fan.

Note that both portable HEPA air cleaners, box fans and furnace filters often sell out in stores when fire season comes around, so it's a good idea to stock up beforehand.

Remember, we share the air – let's keep it fresh and clean!

For more information, visit:

Originally published June 3, 2022