industry. Manufacturers and fire safety officials have raised safety concerns about widespread use of heat-generating catalysts on lawn and garden equipment. Safety studies beyond normal EPA and CARB practices are ongoing; the committee did not have enough information to assess safety concerns fully.
As a result of a 2003 law passed by Congress, small SI engines form a new regulatory category different from other mobile sources. California may set a second standard for those sources; however, the California standard for small SI engines is the only California standard that other states may not adopt under CAA section 177.
Some states have devised nonregulatory, incentive-based emissions-control programs for mobile sources. These programs to date have provided emissions control from mobile sources that would not otherwise have been provided by regulation.