Decades of well-established research have linked nitrogen dioxide, or NO2, to respiratory conditions such as asthma and chronic obstructive pulmonary disease, which especially affect children and older adults. This harmful link is so well established that some states have begun banning gas appliances in new construction. And now a new study has shown in stark detail just how long and far this gas spreads and lingers in a home.

By sampling homes across the U.S., the researchers found that in many, levels of exposure to NO2 can soar above the World Health Organization’s one-hour exposure limit for multiple hours—even in the bedroom that is farthest from the kitchen.

"The concentrations of NO2 we measured from stoves led to dangerous levels down the hall in bedrooms … and they stayed elevated for hours at a time.