Let Air Hub Help you Get Exhausted!

P.O. Box 2535

Mount Pleasant, SC 29465



Air Hub, LLC assists air quality consultants predict the impact on air quality from facilities’ emissions. With the continuously changing ambient air quality regulations, modeling guidelines, and increasingly complex computer algorithms; air dispersion modeling is becoming more demanding. Air quality consultants can feel confident with the knowledge that Air Hub, LLC has an extensive knowledge of modeling requirements. Because air dispersion modeling is our specialty, we are able to accomplish complex modeling scenarios and to stay up-to-date on available modeling programs. Enlist Air Hub, LLC to your team and save your company the cost of labor, training, and software; Enlist Air Hub, LLC to your client’s team and save them the costs of time and unnecessary equipment.

Air Dispersion Modeling

Air dispersion modeling is a set of mathematical equations calculated by EPA approved software. A modeling analysis incorporates site specific information to estimate the concentration of pollutants in the ambient air that would result from an emission source. The resulting pollutant concentrations are then compared with applicable regulations to indicate if a project would result in air quality impacts at the facilities property line, areas beyond the faculties’ property line, or areas open to the public. Air dispersion modeling may be triggered by the planned construction of a new facility, modification to an existing facility, air permit renewal, or by permitting activities at a collocated facility. Any increase in emissions from a new or modified emission source may require a demonstration of compliance with applicable regulations. Often, air dispersion modeling is the most cost-efficient method for demonstrating compliance. Site-specific data including meteorology, topography, property boundaries, buildings, and stack parameters are all included in the air dispersion analysis. Stack parameters include stack height, diameter, exit velocity, emission rates, and temperature. Sources can be modeled as point, area, or volume sources. Depending on the site configuration, unexpected results may occur due to the formation of air cavities. These cavities may be due to the aerodynamic effect of a building that is downwind from a stack.

Ambient Air Quality Standards

National Ambient Air Quality Standards (NAAQS) establish limits of the six principal pollutants considered harmful to public health and the environment. The six pollutants are referred to as the “Criteria Pollutants.” They include: Carbon Monoxide, Lead, Nitrogen Dioxide, Ozone, Particulates, and Sulfur Dioxide. Each pollutant is analyzed for federally established averaging periods. These averaging periods are based on “dosage vs. effect” data. The EPA’s intention is to protect the public health and welfare from both short and long-term effects. The analysis utilizes background concentrations for comparing the predicted ambient air concentration to the regulatory level.

Prevention of Significant Deterioration

The Prevention of Significant Deterioration Standards (PSD) utilize predicted pollutant concentrations from the air dispersion modeling analysis to determine whether concentrations of pollutants will exceed the maximum amount allowed per project. This amount is called the PSD Increment. This “ceiling” is established in an effort to “prevent significant deterioration” of local air quality. The ceiling is lower for areas of special value, such as a national park. It should be noted that a project’s emissions could result in pollutant concentrations less than the PSD Increment and still exceed the Ambient Air Quality Standards (AAQS).

Toxic Air Pollutants

Toxic Air Pollutants are compounds that are identified and regulated on a state by state basis. If a facility emits a toxic air pollutant greater than the threshold determined for that compound. Then the compound must be modeled. The facility may be located in a state that has established multiple averaging periods for a single pollutant.

Noncompliant Results

In the past, facilities could demonstrate compliance with conservative assumptions input in the air dispersion modeling analysis. Increasingly, facilities are finding that the conservative engineering calculations are not predicting pollutant concentrations within the regulatory limits. When this happens, Air Hub, LLC can use advanced modeling techniques such as a particle distribution analysis or the ozone limiting method. Each facility with non-compliant results will be provided a contribution analysis at no extra charge in order to assist the engineer in developing a plan. Let Air Hub, LLC help you Get Exhausted!

Contact Air Hub, LLC at (843) 284-8699 or info@airhubllc.com.