WA Rev Code § 46.37.390 (2021)
2021 Revised Code of Washington|Title 46 - Motor Vehicles|Chapter 46.37 - Vehicle Lighting and Other Equipment.|46.37.390 - Mufflers required—Smoke and air contaminant standards—Definitions—Penalty, exception.

RCW 46.37.390 Mufflers required—Smoke and air contaminant standards—Definitions—Penalty, exception.(1) Every motor vehicle shall at all times be equipped with a muffler in good working order and in constant operation to prevent excessive or unusual noise, and no person shall use a muffler cut-out, bypass, or similar device upon a motor vehicle on a highway.(2)(a) No motor vehicle first sold and registered as a new motor vehicle on or after January 1, 1971, shall discharge into the atmosphere at elevations of less than three thousand feet any air contaminant for a period of more than ten seconds which is:(i) As dark as or darker than the shade designated as No. 1 on the Ringelmann chart, as published by the United States bureau of mines; or(ii) Of such opacity as to obscure an observer's view to a degree equal to or greater than does smoke described in subsection (a)(i) above.(b) No motor vehicle first sold and registered prior to January 1, 1971, shall discharge into the atmosphere at elevations of less than three thousand feet any air contaminant for a period of more than ten seconds which is:(i) As dark as or darker than the shade designated as No. 2 on the Ringelmann chart, as published by the United States bureau of mines; or(ii) Of such opacity as to obscure an observer's view to a degree equal to or greater than does smoke described in subsection (b)(i) above.(c) For the purposes of this subsection the following definitions shall apply:(i) "Opacity" means the degree to which an emission reduces the transmission of light and obscures the view of an object in the background;(ii) "Ringelmann chart" means the Ringelmann smoke chart with instructions for use as published by the United States bureau of mines in May 1967 and as thereafter amended, information circular 7718.(3) No person shall modify the exhaust system of a motor vehicle in a manner which will amplify or increase the noise emitted by the engine of such vehicle above that emitted by the muffler originally installed on the vehicle, and it shall be unlawful for any person to operate a motor vehicle not equipped as required by this subsection, or which has been amplified as prohibited by this subsection. A court may dismiss an infraction notice for a violation of this subsection if there is reasonable grounds to believe that the vehicle was not operated in violation of this subsection.This subsection (3) does not apply to vehicles twenty-five or more years old or to passenger vehicles being operated off the highways in an organized racing or competitive event conducted by a recognized sanctioning body.[ 2006 c 306 § 4; 2001 c 293 § 1; 1977 ex.s. c 355 § 33; 1972 ex.s. c 135 § 1; 1967 c 232 § 3; 1961 c 12 § 46.37.390. Prior: 1955 c 269 § 39; prior: 1937 c 189 § 36; RRS § 6360-36; RCW 46.36.050; 1927 c 309 § 17; 1921 c 96 § 21; 1915 c 142 § 20; RRS § 6362-17.]NOTES:Rules of court: Monetary penalty schedule—IRLJ 6.2.Severability—1977 ex.s. c 355: See note following RCW 46.37.010.Motorcycles and motor-driven cycles—Additional requirements and limitations: RCW 46.37.539.