Wood smoke pollution is a common problem across the world, including in the US. This wood smoke comes from people using wood to heat and cook, as well as from wildfires. The purpose of this research study is to screen individuals to see how they respond to wood smoke inhalation by measuring cells in sputum (or phlegm, that you cough up) to see if there is an increase in the number of cells after exposure. The exposure will be to 500ug/m3 of WSP for 2 hours, with intermittent exercise on a bicycle and rest. The wood is burned in a typical wood stove and piped into the chamber. There is a specific gene that we believe impacts the response to wood smoke exposure, we will also look to see if you have this gene or not (about 40% -60% of people do).