Ask A Trooper

Sgt. Jesse Grabow

Question: I work for a street department and we had a question come up on the safety committee about how far away an exhaust pipe has to be from a window.   We have some trucks that have a hot box on the back that we use in the winter to keep the asphalt warm and we are trying to clarify how far away the exhaust port needs to be from the window or from the entrance to the driver’s window.  If you have any resources or ask explanations we’d appreciate it.

Answer: Here is information from the Code of Federal Regulations (CFR.) 

• Every motor vehicle having a device (other than as part of its cargo) capable of expelling harmful combustion fumes shall have a system to direct the discharge of such fumes. No part shall be located where its location would likely result in burning, charring, or damaging the electrical wiring, the fuel supply, or any combustible part of the motor vehicle. 

• No exhaust system shall discharge to the atmosphere at a location immediately below the fuel tank or the fuel tank filler pipe. 

• The exhaust system of a bus powered by a gasoline engine shall discharge to the atmosphere at or within 6 inches forward of the rearmost part of the bus. 

• The exhaust system of a bus using fuels other than gasoline shall discharge to the atmosphere either: 

• At or within 15 inches forward of the rearmost part of the vehicle; or 

• To the rear of all doors or windows designed to be open, except windows designed to be opened solely as emergency exits. 

• The exhaust system of every truck and truck tractor shall discharge to the atmosphere at a location to the rear of the cab or, if the exhaust projects above the cab, at a location near the rear of the cab. 

• No part of the exhaust system shall be temporarily repaired with wrap or patches. 

• No part of the exhaust system shall leak or discharge at a point forward of or directly below the driver/sleeper compartment. The exhaust outlet may discharge above the cab/sleeper roofline. 

• The exhaust system must be securely fastened to the vehicle. 

• Exhaust systems may use hangers which permit required movement due to expansion and contraction caused by heat of the exhaust and relative motion between engine and chassis of a vehicle.

A portion of state statutes were used with permission from the Office of the Revisor of Statutes. If you have any questions concerning traffic related laws or issues in Minnesota, send your questions to Trp. Jesse Grabow – Minnesota State Patrol at 1000 Highway 10 West, Detroit Lakes, MN 56501-2205.  (You can follow him on Twitter @MSPPIO_NW or reach him at,