What might a low neutral plane indicate?

A low neutral plane can indicate that the fire is likely reaching flashover conditions or is located on a floor below. The neutral plane is the level within a structure where the pressure is equal, and it serves as the transition point between hot smoke and gases rising above and cooler air below. When the neutral plane is low, it often signifies that there is a significant amount of heat and smoke being generated above that point, indicating that the fire may be close to flashover, where the temperature becomes high enough to ignite all combustible materials in the vicinity simultaneously.

Understanding this concept is critical for fire service professionals. A low neutral plane is a dangerous condition that suggests the fire could be more advanced than initially assessed, possibly indicating it is either on the floor above or directly below, where conditions can deteriorate quickly for firefighters and victims. Therefore, recognizing this indication helps in assessing the fire dynamics and taking appropriate action for safety and tactical response.