Maricopa County Air Quality Department Rule 322 caps heavy-duty diesel vehicle idling at five minutes within any sixty-minute period. The rule applies countywide on private and public property and includes specific exemptions for federal idle reductions, sleeper cabs, and emergency operations.
MCAQD Rule 322, adopted under ARS title 49 chapter 3 and Maricopa County Air Pollution Control Regulations, prohibits any heavy-duty diesel vehicle (gross vehicle weight rating over fourteen thousand pounds) from idling more than five minutes in any sixty-minute period anywhere in Maricopa County. The rule covers public roads, private property, loading docks, parking lots, and idling at residences. Exemptions cover sleeper-berth periods between 5 p.m. and 5 a.m. with bunk heater use, traffic congestion, mechanical service, ambulance and fire vehicles, refrigerated trailers running off auxiliary power, and engines participating in EPA SmartWay verified idle-reduction technology. The rule supports federal PM10 and ozone State Implementation Plan compliance.
Each violation of Rule 322 may bring civil penalties up to ten thousand dollars per day under ARS section 49-510 and Maricopa County administrative fines starting at five hundred dollars per occurrence, with repeat offenders subject to enhanced penalties.
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