BY SCOTT T. BURNETTE
Flashover poses a great risk to the fire service. It is imperative that fire service administrators recognize this and take steps to manage the inherent risk of flashover to their firefighters. In Risk Management in the Fire Service (Fire Engineering , 1997, 35-42) Steven Wilder outlines four methods for managing risk: exposure avoidance, loss control, separation of exposures, and contractual transfers. Separation of exposures and contractual transfers are not practical solutions for managing the flashover risk. However, fire service leaders have considered the first two methods, exposure avoidance and loss control.
Exposure avoidance is a risk management tool designed to eliminate firefighters’ exposure to the risk. This method has largely been reactive: When a line-of-duty death or serious injury from flashover occurs, the department then issues an exposure avoidance directive. It usually prohibits firefighters from entering a structure with active fire. Such directives usually make allowances for structures that have known victims inside but strictly limit operations at any other structure fires to defensive exterior attacks only. It’s an extremely effective tool for preventing the loss of or injury to firefighters from flashover. If firefighters are prohibited from entering areas with a high flashover risk, then the department would have a zero risk of flashover losses.
This thinking is commonplace in the fire service, especially after a line-of-duty death in a fire. Comments such as “They should have never been in there in the first place” and “They died saving what? A building that can be rebuilt!” from within the department or from the media sometimes compel administrators to issue exposure avoidance measures.
The major problem with exposure avoidance is that it greatly defeats our purpose as firefighters. Theoretically, it sounds prudent to have a policy that only permits defensive exterior attacks on structure fires. Especially in the wake of a line-of-duty death, it seems to make little sense to risk firefighters’ lives to save property. What is often overlooked when a department uses exposure avoidance to eliminate the flashover risk is the duty that we have as firefighters to our communities.
When a community pays a fire department to provide fire protection, it is entrusting that responsibility to the firefighters of that department. A portion of each taxpayer’s hard-earned income is earmarked every year to pay for fire protection, and we are responsible to provide that service for that taxpayer.
So the question becomes, Can we provide fire protection if we do not enter structure fires? No! Limiting fire protection to exterior attacks because of exposure avoidance accomplishes only one goal—preventing the spread of fire to adjacent structures. Although the department does serve the community by preventing a conflagration, it provides no service at all to the individual taxpayer who has a fire in his residence or business. Exposure avoidance is definitely an effective method of risk management when it comes to flashovers, but it is far from practical.
Firefighting is an inherently dangerous occupation, and the firefighters who go into this line of work accept that risk. Flashovers will happen to firefighters as long as we continue to aggressively fight structure fires on the interior. Since interior attack and search are the only definitive ways to ensure that no one is occupying the structure, we as firefighters must continue to go inside. Life safety is the most important function entrusted to us, so we must accept some risk if we are to accomplish our main purpose.
If exposure avoidance is not practical for preventing firefighter loss from flashover, then we must consider loss control, the last tool in the risk management toolbox. Loss control accepts some risk in the task that must be performed. The goal is to minimize this risk as much as possible and reduce the severity of the loss if it does occur. Loss control in regard to flashover is the subject of much heated debate in the fire service.
There are two opposing theories on controlling loss from flashover. Both focus on preventing the flashover from occurring and minimizing the loss from it if it does occur and agree that proper ventilation goes a long way to prevent flashover. But the two opinions differ on the appropriate methods of water application used to prevent flashover.
Wide Fog Stream vs. Straight Stream
The most common method used by U.S. firefighters is to direct a wide fog stream into the upper atmosphere of the fire compartment. The second method directs a straight or solid stream in the fire compartment’s atmosphere. The difference in these methods may seem trivial, but they have extremely different effects on the fire environment; the firefighters; and, most importantly, the fire victims.
Most of the fire service was taught that the positions on the combination nozzle were “Right for reach, Left for life.” This resulted in firefighters’ believing that if a flashover is imminent, the fog nozzle bumper should be rotated all the way to the left for the crew to get the maximum amount of protection from the fire stream. However, a new approach would replace this statement with “Right is the right position of the stream.” According to this method, a fire stream should be straight or solid if it is going to be used to prevent a flashover.
Wide Fog Pattern
With the wide fog pattern approach to flashover risk loss control, the idea is to apply the fire stream in the area of the fire room that has the highest level of heat. The fire stream is distributed in a wide fog pattern in the upper atmosphere in the fire compartment to maximize steam conversion, breaking up the water droplets to enhance the law of latent heat of vaporization.
This method is by far the least effective for protecting lives. It has been well documented that if this method is used, the victims cannot occupy the structure because of the disastrous consequences they will suffer without personal protective equipment. When this method is employed, performing a thorough search to ensure that there is no possibility of victims is essential. A fire victim will usually occupy a space near the floor, an area that is very tenable even in severe fire conditions because the temperature at that level usually does not exceed 150ºF of dry heat. This layer of tenability remains only as long as the thermal balance in the room stays intact. It is well known that using a wide fog stream inside a structure violently disrupts the thermal balance, sending 200ºF to 300ºF temperatures to the floor instantly, even in areas remote from the fire. This eliminates any chance of rescuing the fire victim who has no respiratory protection. It also makes conditions for firefighters very uncomfortable, even through our protective gear. It can be argued that if flashover is not prevented, then the victims and firefighters would die anyway. But, there is a way to prevent flashover and keep the thermal balance in check.
Although it is widely known that water expands to steam at a rate of 1,700 times its original volume, it is not as well known that this expansion rate is only accurate at 212ºF. Structure fire ceiling temperatures commonly approach or exceed 1,000ºF; at this temperature, the water-to-steam expansion rate increases to 4,000 times the original water volume. Although the human body can withstand more than 200ºF of dry heat for a short time, it cannot survive much more than 150ºF of moist heat for any length of time. When a wide fog stream is directed into the 1,000ºF ceiling temperature, enormous quantities of steam envelop the entire structure, and this steam also travels to far remote locations from the fire room, again eliminating any chance of rescuing a live victim from the structure. Water can only be as hot as 212ºF, but steam reaches thousands of degrees in temperature, which is not only fatal to the victim but also very uncomfortable and often injurious for firefighters.
The other method of flashover risk loss control is preventing flashover by using a straight or solid stream. This method of attack is similar to the one mentioned above, except that only a tight straight stream from a fog nozzle or a solid stream from a smoothbore nozzle is used at the ceiling instead of a wide fog. The theory behind this method is to distribute the water into the upper atmosphere of the fire compartment while it is still in the liquid form, maximizing the law of latent heat of vaporization where it is most efficient: at the upper strata of the fire gases.
This method maximizes life safety. Because the water is not turned to steam prematurely at the lower gas layers, the thermal balance is maintained, as is the precious tenable layer in which victims are lying. This allows us to prevent flashover as soon as it is detected and makes operations safer for firefighters because they no longer have to search the entire structure for victims as the flashover remains unchecked, intensifying and increasing the risks to the search crew and the victims yet to be found.
Without producing massive quantities of steam, this method maintains the tenability of the structure areas remote from the fire and makes conditions much more comfortable for the attack and search crews. The most important reason this method maximizes life safety is firefighter protection. In preflashover conditions we are trained “Left for life.” This is dangerous to the firefighter. When we crank a fog nozzle all the way to the left in the few seconds we have to prevent a flashover, several things happen:
- Time is wasted adjusting the nozzle pattern all the way to the left.
- A wide fog pattern dramatically reduces the stream’s effective reach, requiring the attack crew to be intimately close with the preflashover conditions. It is much safer for the crew to cool the flashover from the distance afforded by the reach of the straight or solid stream.
- A flashover must be prevented by placing the most gallons per minute (gpm) at the ceiling as possible. A wide angle fog stream by its nature places as much as half of its precious gpm on the floor and lower half of the room.
- Water drops broken up into a fog pattern are quickly evaporated by the intense preflashover heat that is banking down and never have a chance to reach the ceiling where they are needed.
Flashover burns and kills firefighters every year. A major contributing factor to these casualties is the lack of a good risk management program for flashover. The most effective flashover risk management tool is loss control. Although exposure avoidance is effective, it is impossible to do our job properly without entering the structure. Hence, loss control is our only flashover risk management tool. The fire service leader must determine the best way to minimize the effects and occurrences of flashover.
The best, safest, and most efficient way to minimize flashover is to use a straight or solid stream. This method must be taught along with flashover recognition training. Firefighters need to be well trained in recognizing flashover conditions and have the tools to prevent a flashover quickly without disrupting the thermal balance and injuring or killing others in the fire structure.
This information and training must be accompanied by practical experience in live-burn evolutions. Flashover simulators are becoming more popular, and using this important teaching tool can make firefighters better equipped to manage the risk of flashover.
The fire service has been taught to use wide fog streams for so many years that the most difficult challenge the fire service leader has in managing flashover risk is changing the thinking of firefighters. This can only be done by excellent training, practical experience, and making the firefighters a part of the new risk management program to control the loss from flashover.
SCOTT T. BURNETTE is a lieutenant with the Asheville (NC) Fire Rescue Department, where he has worked for nine years, and chief of the Mills River Volunteer Fire Department, where he has volunteered for 16 years. He has an associate’s degree in fire protection technology from Gaston College and a bachelor’s degree in fire safety engineering technology from the University of North Carolina-Charlotte.