89.106 Prohibited controls.§ 89.106 Prohibited controls.
(a) An engine may not be equipped with an emission control system for the purpose of complying with emission standards if such system will cause or contribute to an unreasonable risk to public health, welfare, or safety in its operation or function.
(b) You may not design your engines with emission-control devices, systems, or elements of design that cause or contribute to an unreasonable risk to public health, welfare, or safety while operating. For example, this would apply if the engine emits a noxious or toxic substance it would otherwise not emit that contributes to such an unreasonable risk.[59 FR 31335, June 17, 1994. Redesignated at 63 FR 56995, Oct. 23, 1998; 67 FR 68339, Nov. 8, 2002]