The particulate matter emitted from our buses’ exhaust must meet very rigorous standards per the California Air Resource Board. Part of this includes subjecting particulate matter to extreme heat to reduce the amount emitted from the tailpipe. This process can sometimes lead to an increased smell of “fumes”. Most times we try and do this burn off when no passengers are aboard but there are cases where the bus’s computer will deem it necessary while in service. The smell, although unpleasant, is not harmful to passengers.