Air Quality Modeling

Air Quality Modeling encompasses the analytical methodologies used to simulate the distribution, concentration, and impact of pollutants in the ambient air. Through computational models, our professionals assess emissions from various sources, such as stacks, fugitive indoor sources, and outdoor storage piles, considering meteorological conditions, terrain, and receptor locations to estimate pollutant dispersion patterns, concentrations, and their potential impacts on ambient air quality and public health.

National Ambient Air Quality Standards (NAAQS)

The National Ambient Air Quality Standards (NAAQS) represent pollutant concentration thresholds established by the U.S. Environmental Protection Agency (EPA) under the Clean Air Act to protect public health and the environment. These standards apply to six criteria pollutants—ozone, particulate matter, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. Compliance with NAAQS is assessed using ambient air quality data and modeling techniques to determine whether existing and projected pollutant levels meet these standards.

Significant Impact Level Modeling

The Significant Impact Level (SIL) is a threshold concentration defimed by the EPA that represents a level of air quality impact that is minimal compared to the NAAQS and is used for evaluating the significance of new or modified emissions sources on NAAQS attainment. When modeled impacts of a new or modified emissions source exceed SILs for specific pollutants, further detailed analysis is required to ensure compliance with ambient air quality standards and Prevention of Significant Deterioration (PSD) increments. SILs serve as a regulatory tool to prevent unacceptable impacts on cumulative pollutant levels in attainment and non-attainment areas.

Hazardous Air Pollutants (HAP) Modeling

The Clean Air Act designated a list of 188 Hazardous Air Pollutants (HAP) that are known to cause cancer and other serious health issues upon high levels of exposure. While no federal ambient air quality standards exist for these pollutants, various states maintain their own ambient standards and may require modeling of HAP emissions as part of the air permitting process to demonstrate compliance.

Our team of experts can assess you facility's unique risks, and offer a comprehensive plan to complete a thorough air model.

Our Expertise

Using AERMOD and other software, we can model for a wide variety of pollutants at various types of facilities and sources. National Ambient Air Quality Standards (NAAQS) modeling typically involves a two-phase approach:

Phase 1

A Significant Impact Level (SIL) analysis is conducted by modeling only the proposed or modified emissions.

Phase 2

If SIL concentrations exceed thresholds, a comprehensive analysis is performed, incorporating all emission sources at the facility—existing and proposed—alongside measured background concentrations, and the results are compared to the NAAQS.

The EPA may also provide a list of nearby offsite emission sources to supplement or replace background data if unavailable. In cases of NAAQS exceedances, contributions from the facility and offsite sources must be evaluated. Additional pollutants are assessed against applicable standards, incorporating background data when available. Oftentimes total facility emissions are not a likely cause of violation of air quality standards when assessed with other outside impacts. An assessment of your facility(s) may be required to determine the scope of work and process for data collection.

We Model for these Pollutants

NAAQS:

PM10

PM2.5

Carbon monoxide

Lead

Ozone

Sulfur dioxide

Nitrogen

Volatile Organic Matter (VOM)

Hazardous Air Pollutants (HAP)

Greenhouse gases:

Carbon monoxide

Nitrous oxide

Heavy metals:

Arsenic

Cadmium

Chromium

Mercury

Total suspended particulates

Ultrafine particulate matter

Odorous and nuisance compounds:

Hydrogen Sulfide

Mercaptans

Amines

Sulfur compounds

Methane

Ammonia

Industry-specific emissions (acid gases):

Hydrochloric Acid

Hydrofluoric Acid

Dioxins

Furans

Silica Dust

PAH

Deposition products:

Acid Deposition

Particulate Deposition

NHx

NOx

Combustion byproducts:

CO

Carbon Black

Bioaerosol

We Model for these Facilities

Urban facilities

Rural facilities

Manufacturing:

Food

Flavors

Metals

Electrical Particals

Paint

Facilities with Combustion Emissions Sources:

Natural Gas

Oil Generators

Metals

Electrical Particals

Boilers

Universities

Hospitals

Generating stations

Laboratories

Tank farms

We Model for these Sources

Point sources

Volume sources

Area sources

Line sources

Long buildings with continuous vents

Buyant line sources

Flares:

Oil and gas facilities

Wastewater treatment plants

Open Pit:

Quarries

Mines

Get in Touch with Our Experts

Contact us to request more information.

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