4 Minute Engine Coverage

Importance of 4 Minute Engine Response

Fire growth - the rate of spread and the intensity of the fire - is directly linked to the time it takes to initiate fire suppression operations.  As a rule, a fire doubles in size for every minute that passes without the application of aggressive fire suppression measures.  In less than 30 seconds a small flame can rage completely out of control and turn into a major fire.  During fire growth, the temperature of a fire rises to 1,000  to 1,200 degrees Fahrenheit.  Flashover (the very rapid spreading of the fire due to super heating of room contents and other combustibles) at 1,100 to 1,200 degrees Fahrenheit may occur in a burning room in as little as 4 minutes, depending upon its contents.


At flashover, the odds of survival for individuals inside the structure- both victim and rescuer- are virtually non-existent.  The 4-minute goal for arriving fire suppression companies is therefore critical. NFPA 1710 (see excerpt at right) recognizes this fundamental aspect of response and therefore states that a fire department shall establish the response time objective of “4 minutes or less for the arrival of the first arriving Engine Company at a fire suppression incident.”[1] 

[1] NFPA 1710, § (1)

Quick Navigation

GIS Web-Mapping

The following web map shows the results of the 4 minute coverage analysis. The results are summarized in the table below.


Download the map in a printable PDF format.


Interpretting the Results

Currently, engines are capable of responding to 66% of City roads in 4 minutes or less, assuming all units are available to respond immediately upon dispatch.

Table 1: 4 Minute Coverage Results

Fire District

Total Street Length (ft)

Total Streets Covered in 4 Minutes (ft)

% of Streets Covered in 4 Minutes

























The current organization of the Fire Districts fails to meet the NFPA Standard. Only Engine 1 was able to meet the 90% threshold.The remaining Fire Districts fall short of the NFPA standard.

Engine Company 4-Minute Response Capabilities and the Impact of Engine Unavailability

The percentage of roads that do not receive 4-minute coverage, under any circumstances, can be expected to increase as engine companies become unavailable due to emergencies occurring throughout the jurisdiction.  The unavailability of an engine to respond to emergencies within its primary response district creates a gap in services to that area of the community, and a delay in fire department response.  Any delay in response translates directly into a proportional increase in the expected loss of life and property. 


The Importance of 4 Personnel on an Initial Attack

In general, an engine apparatus is the first piece of apparatus deployed when a fire call is received.  The engine company crew is primarily responsible for initial fire attack and victim search and rescue.  Critical tasks include removing the hose line(s) from the engine, stretching the hose to the point of entrance for interior attack, (with a second hose line stretched to protect the exterior), connecting the hose(s) to either the engine pump or water source, and primary search and rescue activities, if enough personnel are available.    In addition, the first arriving company must also assess the situation and determine the extent of the emergency to establish the type and number of any additional resources necessary to mitigate the event. 


The Mansfield Fire Department currently does not deploy 4 personnel on any of the 5 initial attack Engines operating daily. The following table summarizes Engine and Ladder staffing:


Table 2: Staffing of Engine and Ladder Companies







140 E 3rd St

Engine 1


Ladder 1



35 North Brookwood Way

Engine 2



705 Sunset Blvd

Engine 3



1020 South Main St

Engine 4



677 Springmill St

Engine 6



The adoption of the NFPA 1710 Standard minimum staffing requirements was based on scientific evidence and empirical studies conducted throughout the United States and Canada.  Through data collection, analysis of critical tasks, and in-depth training ground simulations, researchers have all found that “inadequate staffing results in the following problems:


    • Delays in the performance of critical tasks;
    • Increased risk to the victims because as the length of the delay is increased, the likelihood of survival decreases;
    • Loss of critical functions;
    • A cumulative effect created by combined delays and lost functions on the part of each crew resulting in an even greater loss of overall effectiveness;
    • Increased physiological stress on firefighters as they try to compensate for the lower staffing level; and
    • Increased risk to the firefighter when aggressive procedures are undertaken without the support necessary to complete them safely.”[1] 


The consensus reached by the professionals, industry trade groups, governments, and individual fire departments that have conducted staffing studies is that many critical tasks are delayed when companies are not staffed with a minimum of four firefighters.[2]  As life safety functions assume first priority, important activities that are often deferred until the arrival of additional personnel include back-up and protection lines, interior suppression, interior rescue, ventilation, use of large hand-held lines, and the establishment of a static water source.  Given that flashover can occur in as between four and ten minutes from the time of ignition, and the response time recommended by NFPA 1710 does not include such variables as discovery, call receipt/processing time, and firefighter turnout time, assembly and complete coordination at the scene must be accomplished in as little time as possible.  Any suppression operations that must be delayed due to insufficient staffing may only exacerbate the situation, forcing procedures to shift from offensive to defensive.


In addition, studies have also found that injury rate and length of disability leave also increase where apparatus are staffed with less than four firefighters.  For instance, an independent consulting actuary hired by Providence, RI found that staffing units with four personnel decreased the risk of injuries, as well as costs associated with these injuries, such as overtime, medical costs, and “injured-on-duty” pay.[3]  The Austin, TX Fire Department staffing study also examined injury reports occurring over a 4-year period and found that firefighters responding on a 3-person crew were 46% more likely to experience injuries than firefighters responding on 4- or 5-person crews.[4]

[1] McManis Associates and John T. O’Hagan & Associates, Dallas Fire Department Staffing Level Study, (June 1984); pp. 1-2.

[2] Most studies also examined the effects of five person crews on tactical operations and found these to be the most effective. It should also be noted that no published study could be found analyzing the effect of a 2 man engine company as this staffing level is considered to be inherently dangerous as no company level task can be carried out without additional personnel.

[3] Swartz, Jonathon, Letter to City of Providence on Cost Savings and Staffing Levels, March 12, 1991.

[4] Austin Fire Department, Austin Fire Department Staffing Study, (March 1993): pp. 4.