Grading the Fireground On a "Curve"

Mark Emery discusses the dangers on the fireground and the need to observe fire growth accurately.


A Benign-Looking Fireground Can Be a Deadly Fireground Two National Institute for Occupational Safety and Health (NIOSH) fatality investigation reports, 98-FO7 and F2004-14, involve firefighters advancing into obscured-visibility, low-heat conditions. In both cases, as they began their advance...


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While reading the following hypothetical scenario, refer back to the series of test photos of the warehouse fire (or better yet, sit at your computer and view the NIST video while reading this section), factor the test data and imagine that a team of firefighters has forced entry through the front door of the warehouse at the precise moment that the eight-minute photo was taken.

Imagine that a team of firefighters with a charged hoseline has just entered through the front door. Based on the test data and accompanying video, entry conditions would have been zero visibility and tolerable heat (approximately 230F three feet above the floor). No smoke is venting out of the door; although dense, the smoke is calm (there is not enough heat to generate positive pressure inside the 4,500-square-foot warehouse). There is no evidence of hostile fire conditions. These observations are confirmed with a thermal imaging camera. The team advances 15 feet from the front door and the team leader re-evaluates conditions: visibility is still zero, he doesn't sense uncomfortable heat and the thermal camera shows that the temperature has actually dropped a few degrees. The team leader can hear a chain saw operating above -- vertical ventilation is in progress, but not complete.

After advancing nearly 45 feet, the team leader reports to the incident commander that the team cannot locate the fire. (Because we have the test data and the test video, we know fire cannot be located because there is no fire to locate; the flames are gone because of lack of oxygen.) A second team with a hoseline appears and, shoulder to shoulder, the two teams advance, searching for the fire. (The first team leader thinks to himself: Zero visibility, low heat confirmed by the thermal imaging camera -- this is basic firefighter stuff, just like during recruit school. What could possibly go wrong?)

Based on conditions and the drop in temperature, both team leaders believe that they entered the warehouse early on the fire-growth curve. They believe that somewhere something has been smoldering for some time, perhaps hours, filling the warehouse with smoke. (Of course, we know that they are correct -- something is smoldering, not for hours, but for just a few minutes.) Three minutes after entering, their thermal imaging camera shows that the temperature has continued to drop. Both team leaders are confident that conditions are improving, even though visibility is still zero.

It has been three minutes since the team forced entry and began to advance into the warehouse. Now 75 feet from the front door, the team leader is suddenly aware of heat. They still have not located the fire. The teams advance for another minute until both team leaders sense that the temperature is uncomfortable; this is confirmed by the thermal imaging camera. Team members are also aware that the heat is uncomfortable. The team leaders direct the teams to withdraw. As each team follows its hoseline toward the door, the incident commander orders all interior teams to withdraw. (The incident commander has noticed smoke where there hadn't been smoke when he arrived. Smoke could be seen coming from roof, along the top of the walls -- and from the front door.)

On their way down the ladder after completing vertical ventilation, the truck company reports that roof conditions are deteriorating. Inside the warehouse, firefighters scramble to withdraw, but are hampered by zero visibility, rapidly increasing heat, and chunks of ceiling and other debris falling around of them. No need to check the thermal imaging camera, each team member is acutely aware that it is uncomfortably hot. Inside the warehouse, confidence is being eroded by panic. Although the teams never do locate fire, the fire locates them.

Call to Action

Perhaps your most important consideration during the size-up of a fire within a building is determining on which side of the fire-growth curve you have arrived. Entering and advancing on the no-value side of the curve can place your firefighters at great risk. It is imperative that the significance of the fire-growth curve be embedded into your long-term memory so that it can be conjured at three in the morning during size-up. Don't rely on what you see through the windshield; don't rely on your thermal imaging camera.