An Air Carrier First Officer reported that because the DAY Airport Rescue and Fire Fighting equipment left for an off airport fire they could not depart for their destination until the equipment returned.

Narrative

Ground Control instructed us to taxi to Runway 24L; cross Runway 18; and included a wheels up time for our destination in approximately 10 minutes. We taxied as instructed and switched to Tower frequency approaching the end of 24L. Tower then informed us that the airport's CFR (crash fire rescue) was not available and that he would be releasing us in 1 minute and 4 seconds to our destination. The Captain and I briefly discussed if takeoff without CFR at the airport was legal. We concluded that a call to Dispatch was necessary. While the Captain called Dispatch; I informed the Tower that we needed time to make a call; and that we were concerned about the legality of a 121 operation at an airport without CFR. The Tower informed us that the airport fire department had responded to a fire call outside of the airport perimeter; possibly at a local hotel; and was not sure how long they would be off the airport property. While we waited for a response from our Company; one other air carrier aircraft taxied out; but did not depart. Also; another air carrier aircraft landed. Approximately 15 to 20 minutes after we were informed of 'CFR not available'; the Tower stated that the fire department had returned to the airport property. We departed. During deplaning; a pilot passenger passed a note regarding FAR 139.319; which he had available and consulted during the flight. Based on the information provided; it appears that the DAY fire department should not be leaving the airport to respond to calls outside the airport.