California Air Resources Board

CARB Mobile Source and Fuel Regulations

CARB has broad authority over fuel and on- and off-road mobile sources, with some exceptions such as engine standards for aircraft and locomotives.  CARB can also establish in-use requirements and mandate emissions limits for fuels and new mobile source engines.  For many mobile source categories, zero emission technologies are already commercially available or in the demonstration phase.  Deploying these technologies in communities with high cumulative exposure burdens can provide local air quality benefits and contribute to regional efforts to achieve air quality standards. 

Recent CARB plans include a suite of new regulations CARB is developing to reduce emissions from mobile sources and fuels:

State Strategy for the State Implementation Plan

Community Air Protection Blueprint

Short-Lived Climate Pollutants Reduction Strategy

Scoping Plan

Air Toxics Hot Spots Program

The legislature established the Statewide Air Toxics Hot Spots Program[1] (Hot Spots Program) to address the health risk from toxic air contaminants at individual facilities across the State.  The Hot Spots Program includes several components to collect emissions data, identify facilities having localized impacts, ascertain health risks, notify nearby residents of significant risks, and reduce those significant risks to acceptable levels.

Under the Hot Spots Program, air districts are required to set a threshold for facilities that pose a significant health risk and prioritize facilities for health risk assessments.  Those facilities that are found to have a significant health risk must notify all exposed persons.  Air districts also establish a risk value above which facilities must conduct a risk reduction audit and emissions reduction plan.  Facilities must develop these health risk assessments, risk reduction audits, and emission reduction plans.  CARB provides technical guidance to support smaller businesses conducting health risk assessments and developing emissions reduction plans.  Statute prescribes penalties for failure to comply, including civil penalties on facility operators for failure to submit a complete risk reduction audit and emission reduction plan or failure to implement the measures set forth in the plan.

CARB Mobile and Stationary Airborne Toxic Control Measures

CARB has the authority to adopt measures specifically to reduce emissions of toxic air contaminants from non-vehicular and vehicular (mobile) sources, known as Airborne Toxic Control Measures (ATCM).[2]  These regulatory measures can include process requirements, emissions limits, or technology requirements.  The air districts have statutory enforcement requirements once CARB adopts a non-vehicular ATCM. 

CARB's Current ATCMs database contains information on ATCMs.

Air District Rules

Air districts establish rules to reduce emissions from stationary and area-wide sources.  Prohibitory rules set emissions limits, ban certain practices, or require the use of certain technologies.  The air districts also adopt other types of rules including transportation control measures, indirect source rules, and best available retrofit control technology (BARCT) determinations for sources in nonattainment areas.  BARCT determinations are reviewed and strengthened periodically by air districts to reduce emissions from existing sources of a particular source type.  Updated BARCT determinations that require the cleanest technology and practices can provide emissions reductions from existing sources. 

CARB’s District Rules Database contains information on air district rules. 

Enforceable Agreements

There may be opportunities for communities, CARB, the air districts, cities, counties, other public agencies, and/or industry to develop enforceable agreements.  There are several examples of these types of agreements working in practice.  Enforceable agreements between CARB or air districts and industry can result in voluntary adoption of the cleanest technologies or practices and provide assurance that emissions reductions will be realized.  In addition, project developers and local communities may enter into community benefit agreements which can give communities a formal voice in how projects are developed.

Examples of existing enforceable agreements include:

CARB Rail Emission Reduction Agreements

Air district permitting requirements

Air districts issue permits to stationary sources[3] allowing them to operate within emissions limits.  Permit limits are usually updated when a facility installs new equipment or modifies their existing equipment.  Air districts set emissions thresholds above which sources are subject to stringent emissions control requirements.  For sources that exceed these thresholds, air districts determine the best-achievable emissions limit for each equipment type at that time, known as best available control technology (BACT) or best available control technology for toxics (T-BACT).  Air districts must consider other BACT and T-BACT determinations during the permitting of a new or modified source.  Statute requires air districts to use CARB’s Technology Clearinghouse when updating their BACT determinations for stationary sources.[4]

Enforcement of CARB and air district rules and regulations

CARB and the air districts have the authority to enforce air quality rules and regulations and can support additional emissions reductions through enforcement activities that identify sources emitting above allowed levels.  Enforcement efforts also serve to deter non-compliance from other parties.

CARB Enforcement

In-Use Testing

In-use testing is designed to identify cases where technologies are not functioning at their certified emissions levels.  In some cases, this can lead to product recalls, and can be used to identify opportunities to target equipment turnover.

Incentive resources

Information on Air Pollution Incentives, Grants, and Credit Programs

Cool California Funding Wizard