Respiratory infections among junior high school students in upper northern Thailand: The role of building dampness and mould, biomass burning and outdoor relative air humidity (RH)

•Childhood respiratory infections can be associated with dampness and indoor mould.•Dry season and outdoor air humidity (RH) can increase respiratory infections.•Smoke from indoor and outdoor biomass burning can increase respiratory infections.•Living in a wooden house can decrease childhood respiratory infections.•Season can modify the effects of household exposure on respiratory infections.