How Hoods Can Help Detect Flashover
Structural hoods not only protect face from radiant heat and combustion products but can serve as an early warning device for firefighters
By Mike McKenna
The firefighting hood has finally become an accepted piece of the structural ensemble — or has it? Recently I was confronted again with the argument that the firefighter of today is overprotected and that the hood is at least partly to blame because firefighters can no longer feel the heat using their ears. But think back to when you were a child and suffered sunburned ears and did not know they were even hot to begin with.
Given the evolution of the fire environment, firefighters are not overprotected. The structural firefighting environment is arguably more dangerous than it has ever been. I also argue that the hood can actually be an early warning indicator to thermal saturation of the protective ensemble and a trigger to situational dangers, one that is much better than exposing the uncovered ears to the fire environment. With this recognition, firefighters must use their experience and knowledge to identify worsening conditions.
Let us remove the fact that due to a variety of reasons firefighters fight fewer structural fires than in years past. The ones we are fighting today can be considered more challenging. In 1996, Randal J. Lawson, of the National Institute of Standards and Technology (NISTR 5804), examined the fire environment and found that the United States has experienced "significant changes in fuel growth characteristics" because of increased fuel loads from synthetic building materials.
According to the NIST research, bedroom fire loads alone have increased from 13.2 lb/ft2 to 25.7 lb/ft2. That is nearly a doubling of the fire load. This new and increased fire load burns much hotter than in the decades before. While we have fewer fires, they are hotter than before and produce significantly higher heat release rates.
Interior furnishings burn faster and hotter than in the past. In addition, modern construction techniques shorten the time when it is safe for firefighters to be in the interior. The new fire environment has more contents and these contents burn hotter and faster, and the buildings are less resistant to fire.
The structural hood
The hood protects our face from radiant heat, keeps combustion products off of them and can be used as an early warning device. After conversations and interviews with several firefighters who have been in flashover conditions, I have noted one consistent theme. In each instance, firefighters who had been in flashover, near flashover, or unusually high radiant heat situations, stated that they felt as if their hood had become dislodged or had not been put on properly.
I began to conduct this research after a friend of mine survived a flashover in an automotive upholstery shop. He stated that when he was stuck on the floor, he felt as if his hood was not on correctly. He attempted to adjust it with his gloves on, and ended up dislodging it from its original and correct position, which led to facial burns.
After that incident, I continued to study and to question. The research revealed that the average firefighter dons their turnouts in roughly the following order. The hood is donned first, or early in the donning process, and then the facepiece. The hood is then pulled up and secured around the facepiece with the bare hands. The helmet is next. The gloves are put on last. It all seems to indicate that because the hood is put on with bare hands, it is put on correctly.
The hood is a protective interface device and because of that it has a thermal protective level less than the rest of the structural garment. The traditional hood is made of knit material allowing for more comfort and breathability. Nevertheless, like all textiles used in the fire service, it does become saturated with heat over time.
The saturation rate of the hood is faster than the rest of the structural garment. If the hood fits reasonably snug against the face, ears and neck, the heat will diffuse throughout the hood material and find its way to your face – not just your ears. When the hood becomes saturated with heat, it will feel as if it is not even there and the face will become hot all over. That is the clue that the heat has saturated your garments and it is time to look around.
Heat saturation and situational awareness
The thermal saturation of the hood, although the rest of the ensemble has not reached that point, indicates that the firefighter has been exposed to significant radiant heat. It may not initially feel like it, and it may not look like it; however, this is a critical time to stop and to evaluate the current situation.
If you find yourself in this scenario, don't take it lightly. The firefighter must ensure that they are where they should be and that the fire environment is not sliding into a potentially dangerous situation.
It is important to remember that the saturated garment is not going to release heat as long as it is still in the heated environment. If your hood is saturated with heat and is hot, it is important that you confirm that the situation is a safe one and the immediate goal is achievable.
When your face feels like you are not wearing that hood you just donned, take it as a warning. Look around and make sure that the situation is a safe one. The saturated hood can be a key to situational awareness.