A study conducted by UC Berkeley environmental scientists found that certain behaviors can significantly reduce the amount of wildfire smoke inside people’s houses.

The study found practices such as closing windows and doors and installing filtration systems can reduce wildfire smoke infiltration. Additionally, the study found infiltration was lower in newer buildings and those with air conditioning units as opposed to older buildings.

“The implications of the study is that people really can protect themselves in indoor spaces from wildfire smoke and with data on indoor concentrations and outdoor concentrations you can actually see how effective your efforts to reduce the infiltration of smoke into your home are,” said campus environmental studies and policy management, or ESPM, professor Allen Goldstein, a supervisor of the research.

According to Yutong Liang, a graduate student in the ESPM department and project lead, the researchers used PurpleAir sensors to measure the PM2.5 inside and outside houses to create indoor/outdoor PM2.5 ratios.

PM2.5 is a class of air pollutants including inhalable particles that are usually 2.5 micrometers in diameter, according to the Environmental Protection Agency. PM2.5 can be emitted from fires, making it a concern for communities near active wildfires.

Researchers then associated the ratios they found and discovered that newer buildings protect residents better.

These findings suggest that older buildings in regions such as the Berkeley Hills are more vulnerable to smoke infiltration, according to Deep Sengupta, a postdoctoral researcher in the ESPM department and study co-author.

“Berkeley has a lot of older buildings, especially in the Berkeley Hills area, where you have very beautiful weather,” Sengupta said. “You don’t use AC a lot and these buildings are not well-protected. When a smoke bloom comes in and it infiltrates your house, you are in trouble. Our study was able to identify some places where the buildings are not well protected in the San Francisco, Albany, El Cerrito and Berkeley area where people don’t have AC inside their houses.”

For houses close to wildfires, smoke levels can become hazardous if people leave their houses open, Liang said in an email. According to Goldstein, exposure to smoke and particulate matter could lead to cardiovascular and pulmonary health impacts.

Liang noted that there are some limitations to this study. For example, houses with PurpleAir sensors may not be representative for the entire distribution of buildings.

PurpleAir owners live on properties that have an average value that is 21% greater than median property values for their respective cities, Liang added.

“Given anticipated increases in wildfire smoke in the coming decades, it is critical to evaluate these findings in other settings, including in lower-income communities and in other climate regions affected by wildfires,” Liang said in an email.

According to Liang and Goldstein, such filtration systems could be bought for less than $100.