(Portland, OR) -- TriMet, Sound Transit and the University of Washington are conducting a study on second-hand fentanyl smoke in buses or trains. TriMet is seeing an increase in fentanyl smoking by passengers. There hasn't been much research on the effects of second-hand fentanyl smoke. Last April, TriMet began stopping trains and buses when there were reports of smoke fumes on board. The doors are opened to air out the vehicle before it returns to service. TriMet rules allow people who smoke to be cited or excluded from transit.