A Corsi-Rosenthal air purifier built by Liz Hradil is seen at her home in Syracuse, N.Y., after wildfire smoke covered much of New York Wednesday, June 7, 2023. The method involves taping four air filters together with a box fan. Experts say the DIY method is highly effective against filtering air indoors against wildfire smoke. (Liz Hradil, Associated Press/The Minnesota Star Tribune)

On really hazy days, Felicia Neves doesn't leave her house.

This summer has been particularly tough for the 36-year-old Shieldsville, Minn., woman, who was diagnosed with asthma as a child. So far, the Minnesota Pollution Control Agency has issued warnings about poor air quality from smoke or ozone on 26 days.

Air quality isn't just a concern for those with asthma. People statewide and nationwide are rushing to buy air conditioners, air filters and masks. But there's also a DIY way to get cleaner air in your home. It's called the "Corsi-Rosenthal box," named after its inventor. All you need are pleated air filters, a box fan and some duct tape.

In some cases, the homemade hack is more effective than standard air purifiers, said Kathleen Norlien, an environmental research scientist at the Minnesota Department of Health.

"It's very effective because it provides even more surface area on how to collect the particulate," she said. "You've got a greater surface area and it's low-cost."

The hack works by duct taping one MERV 13 furnace filter onto each of the four sides of a window fan, then positioning the fan so it sucks air through the filters and blows it into the room. (The open side of the fan cube is placed on the floor.) Be sure to fill all the gaps with duct tape. That's it.

The DIY filter has been so successful that it's been used in classrooms on the West Coast as fires rage, according to Norlien.

With climate change and Minnesota's continuing drought conditions, it's likely that we'll experience more wildfire smoke in the skies this summer, Norlien said.

Here are several resources to help:

The Minnesota Department of Pollution Control Agency puts out a map of air quality and alerts in the state with the help of meteorologists. Air quality forecasts have become more accurate over the years, said Amy Barrett, communications officer at the Minnesota Department of Health.

Additionally, the city of Minneapolis offers free asthma inspections for families with people under the age of 21 to identify triggers in the home. The program also delivers free HEPA air cleaners, vacuums, allergen pillows and mattress covers.