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Source: Emissions and Dispersion Modeling System (EDMS) User’s Manual , FAA-AEE-07-01 (Rev. 10 – 06/07/13), June 2013, 

http://www.faa.gov/about/office_org/headquarters_offices/apl/research/models/edms_model/media/EDMS_5.1.4_User_Manual .pdf, and Chapter 7, Organic Liquid Storage Tanks, of EPA's AP-42, http://www.epa.gov/ttnchie1/ap42/ch07/. 

## A5.3.2 Cooling Towers 

Some airports are likely to have a power generating facility associated with its activities, which in turn might also have cooling towers. Cooling towers are heat exchangers that are used dissipate large heat loads to the atmosphere. Although cooling towers can be classified several ways, the primary classification is dry or wet tow ers, and some hybrid wet -dry combinations exist. Dry-cooling towers use air instead of water to cool the steam exiting a turbine . Wet, or evaporative, cooling towers rely on the latent heat of water evaporation to exchange between the process and the air passing through the cooling tower. In hybrid wet -dry systems, both wet and dry components are included in the system, and they can be used separately simultaneously for either water conservation or plume abatement purposes. 

Cooling towers may range in size from ones used for small air conditioning to large power plant cooling towers. Air pollution control equipment such as drift eliminators are typically used cooling towers. These capture water droplets entrapped in the air stream that otherwise would be lost to the atmosphere. Because the drift droplets generally contain the same chemical impurities as the water circulating through the tower, these impurities can be converted to emissions. Drift droplets may evaporate before being deposited in the area surrounding tower, and they can produce PM 10 emissions. PM 10 emissions are generated when the drift 

