The size of firefighting crews has a substantial effect on the fire service's ability to protect lives and property in residential fires, this according to a landmark study issued by the National Institute of Standards and Technology. Four-person firefighting crews were able to complete 22 essential firefighting and rescue tasks in a typical residential structure 30% faster than two-person crews and 25% faster than three-person crews, said Jason Averill, who leads NIST's Engineered Fire Safety Group at its Building and Fire Research Laboratory.

Averill said researchers built a 2-story, 2,000-square-foot "low-hazard" residential structure as described in NFPA 1710 at the Montgomery County Public Safety Training Academy in Rockville, Md. There crews of two, three, four and five firefighters were timed as they performed 22 standard firefighting and rescue tasks, including occupant search and rescue, putting water on fire, and laddering and ventilation. NIST researchers and their collaborators conducted more than 60 controlled fire experiments to determine the “relative effects of crew size, the arrival time of the first fire crews, and the stagger, or spacing, between the arrivals of successive waves of firefighting apparatus,” Averill said.

Researchers found that four-person crews were able to deliver water to a similar-sized fire 15% faster than the two-person crews and 6% faster than three-person crews, Averill said. The four-person crews operating on a low-hazard structure fire completed all the tasks on the fireground an average of seven minutes faster — nearly 30% faster — compared to two-person crews. In addition, four-person crews completed the same number of fireground tasks an average of 5.1 minutes faster — nearly 25% faster —than the three-person crews.

The report also found:

Time to water on fire:

• 10% difference in the water-on-fire time betweenthe two- and three-person crews.
• An additional 6% difference in the water on fire time between the three- and four-person crews. (four-person crews put water on the fire 16% faster than two person crews).
• An additional 6% difference in the water on fire time between the four- and five-person crews (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.
• Four-person crews operated 25% faster than three-person crews.

Primary search:

• 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.

• 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.
• Two-person crews and five-person crews had more than 2 minutes (122 seconds) difference in task completion time.