Both the increasing demands on the fire service – such as the growing number of Emergency Medical Services (EMS) responses, challenges from natural disasters, hazardous materials incidents, and acts of terrorism—and previous research point to the need for scientifically based studies of the effect of different crew sizes and firefighter arrival times on the effectiveness of the fire service to protect lives and property.
To meet this need, a research partnership of the Commission on Fire Accreditation International (CFAI), International Association of Fire Chiefs (IAFC), International Association of Firefighters (IAFF), National Institute of Standards and Technology (NIST), and Worcester Polytechnic Institute (WPI) was formed to conduct a multiphase study of the deployment of resources as it affects firefighter and occupant safety. Starting in FY 2005, funding was provided through the Department of Homeland Security (DHS) / Federal Emergency Management Agency (FEMA) Grant Program Directorate for Assistance to Firefighters Grant Program—Fire Prevention and Safety Grants. In addition to the low-hazard residential fireground experiments described in this report, the multiple phases of the overall research effort include development of a conceptual model for community risk assessment and deployment of resources, implementation of a general sizable department incident survey, and delivery of a software tool to quantify the effects of deployment decisions on resultant firefighter and civilian injuries and on property losses.
The first phase of the project was an extensive survey of more than 400 career and combination (both career and volunteer) fire departments in the United States with the objective of optimizing a fire service leader’s capability to deploy resources to prevent or mitigate adverse events that occur in risk- and hazard-filled environments. The results of this survey are not documented in this report, which is limited to the experimental phase of the project. The survey results will constitute significant input into the development of a future software tool to quantify the effects of community risks and associated deployment decisions on resultant firefighter and civilian injuries and property losses.
The following research questions guided the experimental design of the low-hazard residential fireground experiments documented in this report:
- How do crew size and stagger affect overall start-to-completion response timing?
- How do crew size and stagger affect the timings of task initiation, task duration, and task completion for each of the 22 critical fireground tasks?
- How does crew size affect elapsed times to achieve three critical events that are known to change fire behavior or tenability within the structure:
- Entry into structure?
- Water on fire?
- Ventilation through windows (three upstairs and one back downstairs window and the burn room window),
- How does the elapsed time to achieve the national standard of assembling 15 firefighters at the scene vary between crew sizes of four and five? In order to address the primary research questions, the research was divided into four distinct, yet interconnected parts:
- Part 1—Laboratory experiments to design appropriate fuel load
- Part 2—Experiments to measure the time for various crew sizes and apparatus stagger (interval between arrival of various apparatus) to accomplish key tasks in rescuing occupants, extinguishing a fire, and protecting property
- Part 3—Additional experiments with enhanced fuel load that prohibited firefighter entry into the burn prop – a building constructed for the fire experiments
- Part 4—Fire modeling to correlate time-to-task completion by crew size and stagger to the increase in toxicity of the atmosphere in the burn prop for a range of fire growth rates. The experiments were conducted in a burn prop designed to simulate a low-hazard1 fire in a residential structure described as typical in NFPA 1710® Organization and Deployment of Fire
Suppression Operations, Emergency Medical Operations, and Special Operations to the Public by Career Fire Departments. NFPA 1710 is the consensus standard for career firefighter deployment, including requirements for fire department arrival time, staffing levels, and fireground responsibilities. Limitations of the study include firefighters’ advance knowledge of the burn prop, invariable number of apparatus, and lack of experiments in elevated outdoor temperatures or at night. Further, the applicability of the conclusions from this report to commercial structure fires, high rise fires, outside fires, terrorism/natural disaster response, HAZMAT or other technical responses has not been assessed and should not be extrapolated from this report.
- Of the 22 fireground tasks measured during the experiments, results indicated that the following factors had the most significant impact on the success of fire fighting operations.
- All differential outcomes described below are statistically significant at the 95 % confidence level or better.
Overall Scene Time:
- The four-person crews operating on a low-hazard structure fire completed all the tasks on the fireground (on average) seven minutes faster—nearly 30 %—than the two-person crews.
- The four-person crews completed the same number of fireground tasks (on average) 5.1 minutes faster—nearly 25 %—than the three-person crews.
- On the low-hazard residential structure fire, adding a fifth person to the crews did not decrease overall fireground task times.
- However, it should be noted that the benefit of five-person crews has been documented in other evaluations to be significant for medium- and high-hazard structures, particularly in urban settings, and is recognized in industry standards.
Time to Water on Fire:
- There was a 10% difference in the “water on fire” time between the two- and three-person crews.
- There was an additional 6% difference in the “water on fire” time between the three- and four-person crews. (i.e., four-person crews put water on the fire 16% faster than two person crews). There was an additional 6% difference in the “water on fire” time between the four- and five-person crews (i.e. five-person crews put water on the fire 22% faster than two-person crews).
Ground Ladders and Ventilation:
- The four-person crews operating on a low-hazard structure fire completed laddering and ventilation (for life safety and rescue) 30 % faster than the two-person crews and 25 % faster than the three-person crews.
- The three-person crews started and completed a primary search and rescue 25 % faster than the two-person crews.
- The four- and five-person crews started and completed a primary search 6 % faster than the three-person crews and 30 % faster than the two-person crew.
- A 10 % difference was equivalent to just over one minute.
Hose Stretch Time:
- In comparing four-and five-person crews to two-and three-person crews collectively, the time difference to stretch a line was 76 seconds.
- In conducting more specific analysis comparing all crew sizes to the two-person crews the differences are more distinct.
- Two-person crews took 57 seconds longer than three-person crews to stretch a line.
- Two-person crews took 87 seconds longer than four-person crews to complete the same tasks.
- Finally, the most notable comparison was between two-person crews and five-person crews—more than 2 minutes (122 seconds) difference in task completion time.
Industry Standard Achieved:
- As defined by NFPA 1710, the “industry standard achieved” time started from the first engine arrival at the hydrant and ended when 15 firefighters were assembled on scene.
- An effective response force was assembled by the five-person crews three minutes faster than the four-person crews.
- Based on the study protocols, modeled after a typical fire department apparatus deployment strategy, the total number of firefighters on scene in the two- and three-person crew scenarios never equaled 15 and therefore the two- and three-person crews were unable to assemble enough personnel to meet this standard.
- Three different “standard” fires were simulated using the Fire Dynamics Simulator (FDS) model. Characterized in the Handbook of the Society of Fire Protection Engineers as slow-,medium-, and fast-growth rate4, the fires grew exponentially with time.
- The rescue scenario was based on a non-ambulatory occupant in an upstairs bedroom with the bedroom door open. Independent of fire size, there was a significant difference between the toxicity, expressed as fractional effective dose (FED), for occupants at the time of rescue depending on arrival times for all crew sizes. Occupants rescued by early-arriving crews had less exposure to combustion products than occupants rescued by late-arriving crews.
- The fire modeling showed clearly that two-person crews cannot complete essential fireground tasks in time to rescue occupants without subjecting them to an increasingly toxic atmosphere. For a slow-growth rate fire with two-person crews, the FED was approaching the level at which sensitive populations, such as children and the elderly are threatened.
- For a medium-growth rate fire with two-person crews, the FED was far above that threshold and approached the level affecting the general population.
- For a fast-growth rate fire with two-person crews, the FED was well above the median level at which 50%of the general population would be incapacitated. Larger crews responding to slow-growth rate fires can rescue most occupants prior to incapacitation along with early-arriving larger crews responding to medium-growth rate fires.
- The result for late-arriving (two minutes later than early-arriving) larger crews may result in a threat to sensitive populations for medium-growth rate fires.
- Statistical averages should not, however, mask the fact that there is no FED level so low that every occupant in every situation is safe.
More than 60 full-scale fire experiments were conducted to determine the impact of crew size, first-due engine arrival time, and subsequent apparatus arrival times on firefighter safety and effectiveness at a low-hazard residential structure fire.
- This report quantifies the effects of changes to staffing and arrival times for residential firefighting operations. While resource deployment is addressed in the context of a single structure type and risk level, it is recognized that public policy decisions regarding the cost-benefit of specific deployment decisions are a function of many other factors including geography, local risks and hazards, available resources, as well as community expectations.
- This report does not specifically address these other factors. The results of these field experiments contribute significant knowledge to the fire service industry.
- First, the results provide a quantitative basis for the effectiveness of four-person crews for low-hazard response in NFPA 1710.
- The results also provide valid measures of total effective response force assembly on scene for fireground operations, as well as the expected performance time-to-critical-task measures for low-hazard structure fires.
Additionally, the results provide tenability measures associated with a range of modeled fires.Future research should extend the findings of this report in order to quantify the effects of crew size and apparatus arrival times for moderate- and high-hazard events, such as fires in high-rise buildings, commercial properties, certain factories, or warehouse facilities, responses to large-scale non-fire incidents, or technical rescue operations.