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Current textSource: eCFR

§ 325.91 Exhaust systems.

Current wording, in the annual edition revised as of Oct. 1, 2011.

eCFR (current) ↗
What changedOct. 1, 1996 wording → Oct. 1, 2011 wording (current)+15 added−10 removedHide

A motor vehicle does not conform to the visual exhaust system inspection requirements, 40 CFR 202.22, of the Interstate Motor Carrier Noise Emission Standards, if inspection of the exhaust system of the motor vehicle discloses that the system—
(a) Has a defect which adversely affects sound reduction, such as exhaust gas leaks or alteration or deterioration of muffler elements, (small traces of soot on flexible exhaust pipe sections shall not constitute a violation of this subpart);
(b) Is not equipped with either a muffler or other noise dissipative device, such as a turbocharger (supercharger driven by exhaust gases); or
(c) Is equipped with a cut-out, by-pass, or similar device, unless such device is designed as an exhaust gas driven cargo unloading system.
[40 FR 42437, Sept. 12, 1975, as amended at 75 FR 57193, Sept. 20, 2010]

49 CFR § 325.91 — Exhaust systems.. Text current through October 22, 2026. This wording effective October 1, 2011 to present. Source: eCFR (current), https://www.ecfr.gov/current/title-49/section-325.91. Retrieved from FMCSR.com, https://fmcsr.com/reg/325.91, on October 26, 2026. Unofficial compilation; verify against the official source.

A motor vehicle does not conform to the visual exhaust system inspection requirements, 40 CFR 202.22, of the Interstate Motor Carrier Noise Emission Standards, if inspection of the exhaust system of the motor vehicle discloses that the system—

(a) Has a defect which adversely affects sound reduction, such as exhaust gas leaks or alteration or deterioration of muffler elements, (small traces of soot on flexible exhaust pipe sections shall not constitute a violation of this subpart);

(b) Is not equipped with either a muffler or other noise dissipative device; or

(c) Is equipped with a cut-out, by-pass, or similar device, unless such device is designed as an exhaust gas driven cargo unloading system.

[40 FR 42437, Sept. 12, 1975, as amended at 75 FR 57193, Sept. 20, 2010]

Amendment history

3 distinct wordings on file since Oct. 1, 1996
  1. Oct. 1, 2011 → presentannual editions 2011–2016diff vs. previousviewing
    [40 FR 42437, Sept. 12, 1975, as amended at 75 FR 57193, Sept. 20, 2010]
  2. Oct. 1, 2010 → Oct. 1, 2011annual edition 2010diff vs. previous
  3. Oct. 1, 1996 → Oct. 1, 2010annual editions 1996–2009

A new entry appears whenever the regulatory words change between government snapshots. Day-precise from the eCFR (2017 onward); before that, one snapshot per annual CFR edition (revised as of October 1). Bracketed citations are the Federal Register history printed with the section. Set a case date in the header to read any earlier wording.