Question 1: Is a heat shield mandatory on a vertical exhaust stack?

Guidance: No. However, §393.83 requires the placement of the exhaust system in such a manner as to prevent the burning, charring, or damaging of the electrical wiring, the fuel supply, or any combustible part of the CMV.

Question 2: Does §393.83 specify the type of exhaust system, vertical or horizontal, to be used on trucks or truck tractors?

Guidance: No.