Airing out rooms with fresh air might not reduce exposure to harmful indoor air pollution, a new study finds.

The new study, published in Science Advances, is part of a larger project involving researchers from several universities in the U.S. and Canada, intended to look at how environmental chemicals in the home are affected by everyday activities like cooking. It’s called the House Observations of Microbial and Environmental Chemistry (HOMEChem) study.

The research team wanted to find out what happens to these chemicals after people clean their floors or open a window. To do this, they set up a single-story test home where they could measure in real time the levels of 19 contaminants commonly found in indoor environments. These included isocyanic acid (often produced by cooking or smoking), nitrous acid, and many chemicals sent into the air from building materials and furniture.