Emissions Inventory

Purpose and Method:

Emissions inventories are tools to assess the quantities of pollutants released into the air from various sources.  One set of pollutants that the Environmental Protection Agency (EPA) regulates comprises criteria pollutants and precursors to ozone formation; these pollutants are regulated based on their health and/or environmental effects, and include:

  • Carbon Monoxide (CO)
  • Nitrogen Oxides (NOx)
  • Particulate Matter (PM10 & PM2.5)
  • Sulfur Oxides (SOx)
  • Volatile Organic Compounds (VOC)
  • Lead (Pb)
Inventories summarize emissions from point, area, biogenic, and mobile sources within Clark County.

A second set of pollutants regulated by DAQ are hazardous air pollutants (HAPs).  HAPs are chemicals or chemical classes widely considered to be toxic and to cause adverse health effects. Currently, 187 chemicals are outlined on the HAP list.

Point Sources

Point sources are stationary, commercial, or industrial sources, and are typically included in the State Implementation Plan (SIP). These comprise major sources that emit more than 100 tons per year of any criteria pollutant, 15 tons per year of any HAP, or 25 tons per year of combined HAPs. The inventory information is used to track SIP progress, calculate operating permit program emission fees, fulfill annual reporting requirements to EPA, and supply information to the general public. 

Area Sources

Area sources are stationary sources that are too small or too numerous to be treated as individual point sources. The area source inventory is determined from local demographic information, state energy and agricultural statistical data, and specific information surveys. 

Biogenic Sources

Biogenic sources comprise the natural (non-anthropogenic) component of VOC and NOx emissions, such as forests, vegetation and soils.

Mobile Sources 

The mobile source inventory includes both on-road and nonroad sources. Highway vehicles such as cars, light duty trucks, heavy-duty trucks, and motorcycles using gasoline and diesel fuels are referred to as on-road mobile sources. Nonroad mobile sources include a wide variety of internal combustion engines not associated with highway vehicles, such as locomotives, airplanes, and small residential, recreational, and commercial engines. The emissions are calculated from vehicle miles traveled (VMT), emission factors for highway vehicle classes obtained from EPA's MOVES model, and other EPA-derived factors.

DAQ submits annual emission inventories for Clark County to EPA. In addition, several research projects have been completed to more accurately reflect the emissions in Clark County.  The completed projects are listed below:
Category  Project
Biogenics Emissions Inventory for Clark County, NV (2006) Study to quantify biological emissions from vegetation and land use in Clark County.
Biogenic VOC Emission Inventory Improvement Project (2006) Study to quantify biological emissions from vegetation and land use in Clark County.
Ozone Precursors
Clark County On-Road Vehicle Classification Study (2018) A study that produces new VMT temporal distribution and VMT mix profiles based primarily on two recent data sources: traffic monitor data from the Nevada Department of Transportation (NDOT) and a license plate survey that CE-CERT conducted to capture license plates on high-resolution video. The profiles developed in the study will support DAQ on-road modeling efforts (MOVES) for the next several years.
Analysis From the Clark County Regional Ozone Precursor Studies (2007) Volatile Organic Compounds (VOC) data for Hazardous Air Pollutants
Clark County Consumer and Commercial Products Emissions Inventory (2005) Study to quantify volatile organic compound emissions from consumer products in Clark County and recommend potential control measures.
Clark County Paved-Road Mobile Sampling Technologies (2008) Studies conducted by the DAQ, the Desert Research Institute of Nevada, University of California at Riverside, California and the University of Nevada at Las Vegas on Paved Road Dust Emission Studies in Support of Mobile Monitoring Technologies. Studies compare USEPA AP-42 silt sampling methods with mobile sampling technologies for characterizing entrainable paved-road dust emissions.
Remote Sensing of Gaseous and Particulate Emissions from Onroad Sources (2002) An analysis by the Desert Research Institute of remote sensing technologies for use in evaluating emissions from onroad vehicles.
Carbon_Monoxide_Saturation_Study_2002.pdf (2002)  A detailed assessment of CO concentrations in the Las Vegas Valley.
Computer Modeling:

DAQ performs a wide variety of computer modeling, including demonstration of NAAQS and Increment compliance of stationary sources, air quality management of hydrographic basins, and SIP modeling for attainment and maintenance demonstrations.

For more information on emissions inventories or computer modeling, contact Zheng Li at (702) 455-1621.