City of Morgan Hill Public Safety Master Plan

SECTION 5. RESPONSE TIME ANALYSIS

Response times are typically the primary measurement for evaluating fire and EMS services. Most deployment models have been built around a four-minute initial travel time for EMS and an eight-minute full-force travel time for fires. Though these times have validity, the actual impact of a speedy response time is limited to very few incidents. For example, in a full cardiac arrest, analysis shows that successful outcomes are rarely achieved if basic life support (CPR) is not initiated within four minutes of the onset. However, cardiac arrests occur very infrequently; on average they are 1 percent to 1.5 percent of all EMS incidents. 14 There are also other EMS incidents that are truly life-threatening and the speed of response can clearly impact the outcome. These involve full drownings, allergic reactions, electrocutions, and severe trauma (often caused by gunshot wounds, stabbings, and severe motor vehicle accidents, etc.). Again, the frequencies of these types of calls are limited. Regarding response times for fire incidents, the criterion is based on the concept of “flashover.” This is the state at which super-heated gasses from a fire are released rapidly, causing the fire to burn freely and become so volatile that the fire reaches an explosive state. In this situation, usually after an extended period of time (often eight to twelve minutes after ignition but times as quickly as five to seven minutes), and a combination of the right conditions (fuel and oxygen), the fire expands rapidly and is much more difficult to contain. When the fire does reach this extremely hazardous state, initial firefighting forces are often overwhelmed, larger and more destructive fire occurs, and significantly more resources are required to affect fire control and extinguishment. Flashover has been observed to occur more frequently today due to greater quantities of plastic- and foam-based products in homes and businesses. These materials ignite and burn quickly and produce extreme heat and toxic smoke. Figure 5-1 illustrates the flashover phenomenon and its potential impact on firefighters and fire extinguishment as the fire propagation curve.

14 Myers, Slovis, Eckstein, Goodloe et al. (2007). ”Evidence-based Performance Measures for Emergency Medical Services System: A Model for Expanded EMS Benchmarking.” Pre-hospital Emergency Care.

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