Here are some things to keep in mind to better understand what the Emissions Inventory Reports represent.

1. The District is responsible for preparing inventory reports for facilities subject to the requirements. Emissions included in an inventory are from stationary sources (emitting devices) that are typically required to have District permits. However, stationary sources that are permit exempt may also be included in the inventory. Stationary sources do not include mobile or biogenic sources, or accidental releases.

2. Not all facilities are required to report annually. An inventory may be prepared annually, biennially, or once every four years depending on the applicable requirements specified by Rule 19.3, CARB’s Criteria and Emissions Inventory Guideline Regulations and District policies. Some of the inventories presented in the annual reports may be drafts inventories at the time of publication.

3. The District implements two Emissions Inventory programs: the Criteria Pollutant Emissions Inventory and the Toxic Emissions Inventory (Air Toxics “Hot Spots” Program). Inventories with the header “Emissions Inventory Report” fulfill both the Criteria Pollutant and Toxic Emissions Inventory requirements. Inventories with the header “Criteria Emissions Inventory Report” fulfill only the Criteria Pollutant Emissions Inventory requirements. Though toxic emissions are presented in the Criteria Pollutant Emissions Inventories, it should be understood the toxic emissions presented may be incomplete and are not considered for the Toxic Emissions Inventory.

4. To coincide with the implementation of CARB's Air Toxic Control Measure for Stationary Compression Ignition Engines, the District began including diesel particulate matter emissions in the inventories starting in 2005. Diesel particulate matter emissions are quantified for diesel engines only; and are not quantified for boilers, turbines or any other diesel combustion equipment. Prior to 2005, the emissions from diesel engines were reported as individual toxic pollutants that compose diesel exhaust. After 2005, individual toxic pollutants that compose diesel exhaust and diesel particulate matter emissions are both included in the facility emissions.

5. If the facility's report has an asterisk on the header (for example, "2016 Emissions Inventory Report*"), the facility emissions are based on an average material usage reported by other facilities.

6. The inventory and prioritization scores presented are current at the time of publication. Both the inventory and/or prioritization scores may be in draft, or under revision, and therefore do not always reflect the approved inventory or scores. The reports are subject to change at any time and may not reflect the most recent updates. The District will make best efforts to update the reports periodically in order to present updated information.

Under the “Hot Spots” Program, once the air toxic emissions are quantified, the District is required to prioritize and categorize the air toxic emissions from the facilities subject to the Program. The District utilizes a prioritization procedure which takes into consideration potency, toxicity, quantity of emissions, proximity of the facility to potential receptors, and any other factor that the District finds may indicate that a facility poses a potential risk to surrounding receptors. The prioritization procedure categorizes the facilities as a high (A), intermediate (B) or low (C) priority. Facilities categorized as “high” are required to conduct a Health Risk Assessment to quantify the potential health risk form their emissions. Facilities categorized as “intermediate” may be subject to HRA requirements. Facilities categorized as “low” are not subject to HRA requirements.

The following report provide current prioritization scores for larger stationary sources and it does not include smaller industrial and commercial businesses (e.g. most gas stations, emergency engines, autobody shops, perc dry cleaners).