EPA is seeking comments on draft guidance released June 7, 2011, on design criteria aimed at preventing new heavy-duty diesel engines from running, if selective catalytic reduction systems, which control nitrogen oxide emissions, are not operating properly. 76 Fed. Reg. 32,886 (6/07/11). The draft guidance is intended for manufacturers and describes compliance with regulations at 40 C.F.R. § 86.094-22. Selective catalytic reduction technology uses a chemical reducing agent—diesel exhaust fluid—to reduce nitrogen oxides emissions. Drivers must refill the fluid on a regular basis.

The draft guidance discusses four design criteria to ensure that engines cannot operate if the selective catalytic reduction system fails: warning systems, inducements for drivers to replenish diesel exhaust fluid, identification and correcting the use of a poor quality reducing agent, and tamper-resistant systems. EPA will accept comments on the draft guidance until July 7, 2011.