Many of the incidents that DFD responds to are calls for emergency medical services. Emergency medical services is a system of care for victims of sudden and serious illness or injury. This system depends on the availability and coordination of many different elements, ranging from an informed public capable of recognizing medical emergencies, to a network of trauma centers capable of providing highly specialized care to the most seriously ill or injured. The 9-1-1 emergency number, search and rescue teams, and prehospital and emergency department personnel are some of the critical elements necessary for the EMS system to work. Because medical emergencies are often time-critical, it is important that EMS arrive as quickly as possible. Failure to do so can make the difference between life and death or permanent disability.

In recent years, fire departments nationwide have evolved into multi-functional organizations; no longer providing fire protection only, but a wide variety of services. EMS has been a major part of this evolution. The many benefits of having the fire department involved in EMS, including cost benefits and reductions in death and disability, makes it logical for DFD to provide such service to the community.

All career firefighters in the department are trained at the minimum level of Emergency Medical Technician (EMT); with many certified as Paramedics. EMTs and paramedics work together to provide an outstanding level of patient care in the field. All Denison Emergency Services are Advanced Life Support (ALS) units. What this means to the citizen, is that superior ALS is available with a significantly reduced response time.

During 2003, the Denison Fire Department responded to 5,469 alarms, which includes medical responses, fires and other requests for service.

The Denison Fire Department has the Enhanced 911 Emergency Dispatch System . An emergency caller's address now appears automatically on the 911 dispatcher's computer screen and, once that address is verified, dispatchers can quickly pass the information to firefighters or police. This system allows faster response times for emergency services. It can also help police and fire personnel respond when a caller cannot give their address correctly.

The Denison Fire Department also tests and operates the Emergency Early Warning System, which consists of 6 emergency sirens strategically located throughout the city. Testing occurs on the 1st Wednesday of each month (weather permitting) at 9:00 a.m. Testing includes siren test and Cable One television over-rides. Testing is done in conjunction with Sherman , Bonham and Grayson County .