In every 24-hour HAZMAT course, we teach, we find that students getting their first official dose of “chemical safety” are shocked to find out that most gases at their facility are NOT white in color. Most have seen dozens of videos over their adult lives showing these large white clouds forming during releases of hazardous materials and just figured that what they were seeing was a chemical cloud. So if ammonia (and propane) is NOT a white gas, then why do we see a white fluffy cloud when ammonia/propane is released to the atmosphere? Chlorine gas is not white; it is yellowish-green in color. Why the difference?