An experienced crane operator was running an electrically powered gantry crane in a process building which was in the final stages of construction. Other than the occasional use of a propane-powered forklift, there were no fossil fuel burning pieces of equipment in the building. It was in the late fall of the year and at the afternoon coffee break, the crane operator climbed down from his overhead cab and reported to the first aid attendant that for the past week he was feeling very drowsy and nauseous by late afternoon, but by late evening the feeling of illness would go away. […]