OAR 735-124-0130
Muffler and Exhaust System
(1)
Every vehicle shall be equipped with a muffler in good working order and in constant operation to prevent excessive or unusual noise and annoying smoke.(2)
Vehicles equipped with vertical exhaust pipes located ahead of passenger compartments or open bodies on which workers are transported shall be equipped with deflectors when necessary to prevent fumes from entering passenger-carrying portion of the vehicle. Exhaust pipes directed to rear of vehicles equipped with partially enclosed passenger compartments shall be equipped with deflectors which will direct exhaust fumes to one side to prevent hazardous fumes from being sucked into the passenger compartment.(3)
On buses and all other types of vehicles which have enclosed passenger compartments, the exhaust pipe, muffler, and tail pipe shall be outside the passenger compartment and attached to the chassis and the tail pipe shall extend at least to the rear bumper but not more than three inches beyond.(4)
The size of the tail pipe shall not be reduced after it leaves the muffler on any vehicle.(5)
Exhaust system shall be properly insulated from the gasoline tank and connections thereof by a metal shield at any point where there is 12 inches or less from the fuel tank or tank connections.
Source:
Rule 735-124-0130 — Muffler and Exhaust System, https://secure.sos.state.or.us/oard/view.action?ruleNumber=735-124-0130.