Section 27154 Of Article 2. Exhaust Systems From California Vehicle Code >> Division 12. >> Chapter 5. >> Article 2.

. The cab of any motor vehicle shall be reasonably tight against the penetration of gases and fumes from the engine or exhaust system. The exhaust system, including the manifold, muffler, and exhaust pipes shall be so constructed as to be capable of being maintained and shall be maintained in a reasonably gastight condition.