California Air Resources Board

Transport Refrigeration Units (TRU) are refrigeration systems powered by diesel internal combustion engines designed to refrigerate or heat perishable products that are transported in various containers, including truck vans, semi-truck trailers, shipping containers, and railcars.  Although TRU engines are relatively small, ranging from 9 to 36 horsepower, significant numbers of these engines congregate at distribution centers, truck stops, and other facilities, resulting in the potential for health risks to those that live and work nearby.  Since diesel particulate matter (PM) pollutant emissions have been identified as a toxic air contaminant, CARB adopted (on February 26, 2004 with amendments in 2010, 2011, and 2022) an Airborne Toxic Control Measure (ATCM) for TRUs, TRU generator sets, and facilities where TRUs and TRU generator sets operate.  Please see more information about this rulemaking at:  2004 TRU ATCM Rulemaking, Rulemaking and Final Regulation Order with 2010 Amendments, TRU ATCM 2011 Regulatory Activity, and Rulemaking and Final Regulation Order with 2022 Amendments.