How Does the Small Engine Rule Work?

The regulation (commonly called Phase 1) sets allow- able exhaust levels for hydrocarbons, carbon monoxide, and NOx from small engines of 25 HP or less. The rule applies to all small engines produced after September 1, 1997—with some earlier and a few later. Allowable emission levels vary depending on engine size and use.

EPA works directly with the engine manufacturers to assure they comply with the regulations. Before an engine manufacturer can sell a regulated engine model in the U.S., it must obtain a certificate of conformity from EPA. To obtain a certificate of conformity, the engine manufac- turer must provide test data along with other information demonstrating that the engine model meets the applicable emission standards.

The Agency requires that the engine manufacturer label each certified engine to indicate compliance with the small spark-ignition engine rule. The language may read “this engine conforms to Phase 1 U.S. EPA regulations for small nonroad engines.” Some engine labels, however, will feature language indicating compliance with both EPA and California regulations. Emission labels will be found on the engine, or if the engine label is obscured, on the piece of equipment itself.