An emergency services key (e.g., ESQK or ESRK) is guaranteed to be available from a limited size ESQK pool. A plurality of ESQKs are grouped into a pool of emergency service keys “ESQK Pool ID”, each including anywhere from 1 to N number of ESQKs. Each ESQK preferably has a “Timestamp”, information relating to the specific emergency E911 call (“Call Data ID”), a guard timer, and an optional hold timer. The ESQK having a Call Data ID=“NULL”, and having the oldest Timestamp, is chosen for selection. If no such ESQK has both Call Data ID=NULL and the oldest Timestamp is found, then the ESQK with merely the oldest Timestamp is selected. The timestamp is reset to a current time plus a guard timer, or hold timer if desired.