By Vicki Schmidt
Firefighters must understand at all times where they are located relative to alpha, bravo, charlie and delta. Knowing the sides of the box — especially when that box is a residential home — is paramount to situational awareness. But as important as it is for a firefighter to know the sides of the box, fire leadership also must know the value of the other two sides: inside and outside. This combined knowledge sets the stage for reducing firefighter injuries and fatalities.
Firefighters and commanding officers everywhere have experienced what high-level technical research from NIST and UL has proved — the buildings reaction to fire in the modern box is different from that experienced by generations before us. Echo the words of one undeniably passionate instructor, Peter Van Dorpe, chief of training at the Chicago Fire Academy, “everything about the built environment has changed."
Few could have predicted the new wave of fire terminology — flow path, heat release, ventilated limited and “the spike” — brought by changes in building construction. Most of these terms still aren't included in the commercial fire curriculum used at most fire training academies. Modern firefighting demands everyone involved understand the knowledge behind the new terminology, and more importantly that everything that happens on every side of the box has a direct and immediate impact on the flow path and in turn — fire behavior inside the box.
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When you pull onto a reported fire scene and see little or nothing showing, always ask yourself “at what stage of the fire are we arriving?" Know the time it takes from the moment the air brakes are set to the time your crew will have water ready to attack the fire. You might arrive post initial growth and the report of “little smoke showing” is masking a ventilation limited fire. Enter into the box of a residential fire, whether VES without immediate isolation or an aggressive attack through the front door and the result will often spawn an immediate secondary growth of a ventilation limited fire; termed by many as “the spike”. The spike occurs when a secure and ventilation limited “box,” the residential home your crew is about to enter, is violated. The air fed to the fire due to the violation, causes the ventilation limited area to flashover. Temperatures during the ventilation limited flashover caused by this second growth phase will often spike to over 1,000 degrees in less than ninety seconds.
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Modern commanders need to know how their commanding actions outside the box are going to impact the flow path and resulting fire conditions inside the box. Commanders must be prepared for an immediate change in fire behavior and conditions. If your crew reports “its getting extremely hot in here” order an immediate evacuation. Those words are a red flag that your crew has entered a ventilation limited area and the area will spike. Additionally, the high degree of heat release is negatively impacting the structural components of the building and global failure, usually a ceiling or floor collapse, is imminent. Study research noted by Dan Madrzykowski of NIST and Steve Kerber of UL and you’ll understand the impact of our tactics on ventilation limited fires: how to better recognize them and how to prevent firefighter death and injury due to them.
Change happens, whether it's over a decade of research or a few seconds of fire attack and a resulting flashover. Know where you and your crews are at all times, both inside and outside the box. Additionally, know at all times how you and your crews actions, both inside and outside the box, will impact the flow path, heat release rates, ventilation, and the resulting building behavior.
Vicki Schmidt is a State Fire Instructor II with Maine Fire Services, as well as a training officer and firefighter for Buckfield Fire Department. She also serves on the Maine Fire Protection Services Commission, and the advisory council for Maine Fire Training & Education. Schmidt is the training program coordinator for the Frandford Mutual Aid Fire Training Association and specializes in large-animal emergency rescue and Firefighter I programs for rural departments.
