# 449.2 General definitions.
The following definitions apply to this part:
*Aircraft deicing fluid (ADF)* means a fluid (other than hot water) applied to aircraft to remove or prevent any accumulation of snow or ice on the aircraft. This includes deicing and anti-icing fluids.
*Airfield pavement* means all paved surfaces on the airside of an airport.
*Airside* means the part of an airport directly involved in the arrival and departure of aircraft, including runways, taxiways, aprons, and ramps.
*Annual non-propeller aircraft departures* means the average number of commercial turbine-engine aircraft that are propelled by jet, *i.e.,* turbojet or turbofan, that take off from an airport on an annual basis, as tabulated by the Federal Aviation Administration (FAA).
*Available ADF* means 75 percent of the normalized Type I aircraft deicing fluid and 10 percent of the normalized Type IV aircraft deicing fluid, excluding aircraft deicing fluids used for defrosting or deicing for safe taxiing.
*Centralized deicing pad* means a facility on an airfield designed for aircraft deicing operations, typically constructed with a drainage system separate from the airport main storm drain system.
*COD* means Chemical Oxygen Demand.
*Collection requirement* means the requirement in § 449.11 for the permittee to collect available ADF.
*Defrosting* means the removal of frost contamination from an aircraft when there has been no active precipitation.
*Deicing* mean procedures and practices to remove or prevent any accumulation of snow or ice on:
(1) An aircraft; or
(2) Airfield pavement.
*Deicing for safe taxiing* means the application of ADF necessary to remove snow or ice to prevent damage to a taxiing aircraft.
*FAA Advisory Circular* means a guidance document issued by the FAA on methods, procedures, or facility design.
*Heating degree day* means the number of degrees per day the daily average temperature is below 65 degrees Fahrenheit. The daily average temperature is the mean of the maximum and minimum temperature for a 24-hour period. The annual heating degree day value is derived by summing the daily heating degree days over a calendar year period.
*Normalized Type I or Type IV aircraft deicing fluid* means ADF less any water added by the manufacturer or customer before ADF application.
*Primary Airport* means an airport defined at 49 U.S.C. 47102 (15).