All exhaust systems must be securely fastened to the vehicle and cannot be placed where likely to burn or damage electrical wiring, fuel supply, and any combustible part of the vehicle. Exhaust systems may not be temporarily repaired with patch or wrap material. Location requirements for exhaust systems vary for trucks and truck tractors, buses powered by gasoline, and buses powered by diesel or other fuel.
See 49 CFR 393.83 for full requirements on exhaust system performance and location.