Vehicles that operate entirely in NOx Exempt Areas are exempt from having to meet 2010 engine emission standards are given more time to meet PM BACT.
At its April 25, 2014 board hearing ARB adopted major changes to the NOx Exempt Area provisions.
The NOx exempt areas were the following counties: Alpine, Colusa, Del Norte, Glenn, Humboldt, Lake, Lassen, Mendocino, Modoc, Monterey, Northern Sonoma, Plumas, San Benito, San Luis Obispo, Santa Barbara, Santa Cruz, Shasta, Sierra, Siskiyou, Trinity, Tehama, and Yuba.
The following counties or areas were added: Amador; Butte; Calaveras; Eastern Kern (portion of Kern County within the Eastern Kern Air Pollution Control District); Inyo; Mariposa; Mono; Nevada; Northern Sutter (portion of Sutter County that is north of the line that extends from the south east corner of Colusa County to the southwest corner of Yuba County); portions of El Dorado and Placer that are within the Lake Tahoe Air Basin, Tuolumne.
Text on the NOx exempt provision was, prior to the most recent changes, exceedingly confusing. Fortunately text has been cleaned up. The previous and current requirements are given below:
|Compliance Date||Previous % of all heavier
trucks that must have a
|Revised % of all heavier
trucks that must have a
|Jan 1, 2014||33%|
|Jan 1, 2015||66%||25%|
|Jan 1, 2016||100%||40%|
|Jan 1, 2017||55%|
|Jan 1, 2018||70%|
|Jan 1, 2019||85%|
|Jan 1, 2020||100%|
Note that for larger trucks once a truck has a PM filter it can be taken out of the NOx exempt status until it is subject to replacement (see the larger vehicle BACT by model year replacement schedule). That is, it can be used outside the NOx exempt area from the date it is has PM filter until it have to comply with 2010 engine standards. At that point (when it would be subject to 2010 engine standards) if can classified and labeled again as a NOx exempt area truck.
Also note that any truck retrofit with a DPF before Jan 1, 2014 does not have to meet 2010 engine standards until Jan 1, 2023.
Vehicles designated as NOx area exempt must be labeled when the exemption is used. The labeling requirement is as follows:
The letters NE shall be white block lettering on a black background. Both letters shall be at least three inches high on a five by eight inch background. The label shall be located on the left and right door of the vehicle and in clear view at all times.
ARB has an FAQ on this topic. Click on "NOx Exempt" at:
Truck and Bus Regulation Fact Sheets and Reporting Documents