Metropolitan Washington Airports Authority (MWAA) Monitoring
From The RadioReference Wiki
Some notes about the MWAA Fire Rescue talkgroups
The stations and units and radio "channels" are all of the "300 series". Station 301 and its units (E301, Medic 301 etc) are at Reagan, Stations 302 and 303 and their units (E303, Truck 302, M302 etc) are at Dulles. At Dulles, Station 302 is the main Crash station and is located at south end of runway 1R/19L. Station 303 is located at the airport entry on the NE corner of Rudder Road and Autopilot Drive.
Talkgroup 3A (1648) dispatches incidents for both Reagan and Dulles airports
3B (1632) is Response channel for both airports for routine things like medical emergencies, automatic building alarms
3C (1600) is Incident channel for both airports for major incidents like building fires, large traffic crashes
3L (2640) is Tactical channel used at Reagan for Aircraft emergencies
3M (2656) is Tactical channel used at Dulles for Aircraft emergencies (including "Alerts"). Units responding to Alerts seem to pop up on this channel first, far in advance of a dispatch on 3A. Presumably there is a shout down net from the Tower.
Aircraft Rescue and Fire Fighting units use the call signs "Foam-xxx". ARFF assignments I have confirmed:
Foam 302, 326, 328, 336, 352 & 358 have been heard on Dulles incidents
Foam 331, 337, 345 have been heard on Reagan incidents
It is not unusual to hear a Foam truck from Reagan going in service "to 1600 Pennsylvania Avenue for Standby". This is the White House, so this is apparently when Marine One is arriving or departing.