Apartment dwellers who don’t smoke still can’t escape second-hand smoke completely, but in smoke-free buildings exposure to the tiny particles in cigarette smoke may be cut by half or more, according to a new study.

Researchers in Boston monitored indoor air at public housing projects transitioning to a smoke-free policy and tracked tobacco smoke as it traveled to adjacent apartments and down common hallways.

“If people ever make an attempt at smoke-free housing, this is sort of the perfect environment to do so,” Dr. Elizabeth Russo, lead author of the study, told Reuters Health in a phone interview. “There’s just higher asthma rates and (rates of) other health conditions in public housing than non-public housing.

“An argument can be made that smoke-free buildings are protective of these residents, who are even more vulnerable,” said Russo, a medical scientist at the Boston Public Health Commission.

Past research has shown many of the tiny particles in secondhand smoke to be toxic. Levels of those particles also average three times higher in homes with smoking than without. But smoke can also travel to nonsmokers’ homes through vents or cracks in the walls, and down common hallways.