FIRE DEPARTMENT RESPONSE TIMES VS. FLASHOVER
BY JOHN R. WATERS
Editor`s note: This article is based on a research paper the author submitted in September 1998 as part of the “Strategic Management of Change” course in the National Fire Academy`s Executive Fire Officer Program.
We see it on the news every day–fire blowing out of a structure`s windows, family members weeping over their losses, the news media asking how this could be prevented in the future. Over the past 20 years, more than 115,400 people have died from the effects of fire and more than 580,000 have been injured.1 In 1987, the United States Fire Administration stated: “The United States has one of the highest fire death rates per capita in the industrialized world.”2 The fire service needs to address this problem. We have talked about it for many years and have made some progress, but the problem remains.
For the most part, the local governmental entity provides fire suppression services for a community. In some communities, a for-profit corporation provides such services, with the government attempting to set performance standards. Yet, there appears to be no national consensus regarding fire suppression forces and their response times.
HOME FIRES
According to National Fire Protection Association (NFPA) statistics, 81 percent of civilians who die in fires are victims of residential occupancy fires. It then becomes obvious that if we are to attempt to mitigate the fire problem in the United States, we must address fires in the home.
For the moment, let us step back from structural firefighting and read a performance requirement contained in NFPA Standard 403, Standard for Aircraft Rescue and Firefighting Services at Airports, 1993. Section 1-2.2, “Purpose,” states the following:
The principal objective of a rescue and firefighting service is to save lives. For this reason, the provision of means of dealing with aircraft accident or incident occurring at, or in the vicinity of, an airport assumes primary importance because it is within this area that there are the greatest opportunities of saving lives. This must assume at all times the possibility of, and need for, extinguishing a fire that may occur either immediately following an aircraft accident or incident, or at any time during rescue operations.
To accomplish its stated purpose, Standard 403, section 7-1.3, sets the following performance requirement: “The demonstrated response time of the first-responding vehicle to reach any point on the operational runway should be 2 minutes or less ….”
Now, we return to our element, that of structural firefighting. We could rephrase the purpose section of Standard 403 to address the local fire department, at the same time recognizing where our fire problems lie. We also can state that the principal objective of the fire department is to save lives. For this reason the provision of a means of dealing with a house fire in the community assumes primary importance because the greatest opportunities for saving lives exist within residential occupancies. This must assume at all times the need for extinguishing a fire immediately following ignition.
Would it not, then, be to our advantage to set some type of standard in terms of time for fire department response? The objective would be to intervene in the progress of a fire before it reaches its critical point, the point at which it becomes deadly.
I set out to answer two questions:
1. At which point does a structure fire becomes deadly?
2. What would it take for the fire department to respond in a manner that would make it possible to apply extinguishing agent on the burning material before the fire becomes deadly?
FLASHOVER
My research to find answers to the first question led me to the information that establishes flashover as the point at which fire becomes deadly.
“The onset of flashover is of interest to all individuals concerned with building fire safety,” explains James Milke.3 “This interest is motivated by the fact that, typically, flashover is considered as the point of transition from a `small fire` involving a small number of objects in the room to a `large fire` involving all objects in the room. Once a fully developed room fire exists, life safety for occupants within that room is no longer of concern because the room is obviously untenable after flashover.”
Bukowski and Peacock, who conducted research in 1995 for the Building and Fire Research Laboratory of the National Institute of Standards [now the National Institute of Standards and Technology (NIST)], stated: “The occurrence of flashover within a room is of considerable interest to the fire protection specialist since it is perhaps the ultimate signal of untenable conditions within the room of origin as well as a sign of greatly increased risk to other rooms within the building.4
At the point where they speak of “increased risk to other rooms within the building,” it certainly can be inferred that occupants of those rooms also face this increased risk. As such, flashover is the point at which a fire in a structure becomes deadly.
T. T. Lie echoes that same thought: “During flashover, however, the temperature rises very sharply to such a level that survival of persons still in the room at that stage becomes unlikely. Thus the time interval between the start of the fire and the occurrence of flashover is a major factor in the time that is available for safe evacuation of the fire area.”5
Concerning the toxic effects of fire at the time of flashover, the NFPA Fire Protection Handbook, 18th edition, contains a number of statements that underline the dangers that occur at flashover:
–Gordon Hartzell writes in “Combustion Products and Their Effect on Life Safety”: “Thus, a rapid increase in carbon monoxide yield occurs almost simultaneously with flashover.” (pp. 4-11)
–In the same volume, Thomas Jaeger documents in “Health Care Occupancies”: “Fires that reach flashover produce acutely lethal atmospheres generating thousands of cubic feet of smoke per minute.” (pp. 9-52)
–Edward Budnick, David Evans, and Harold Nelson in “Simplified Fire Growth Calculations” define flashover as follows: “A critical point in room fire growth is an event often referred to as `flashover.` While a universal definition does not exist, this event is generally associated with a rapid transition in fire behavior from localized burning of fuel to involvement of all the combustibles in the enclosure.” (pp. 11-101)
–Richard Custer in “Dynamics of Compartment Fire Growth,” provides a more scientific definition of the phenomenon of flashover. He lists the following triggering conditions for flashover: (1) the upper gas layer in the compartment or enclosure is approximately 6007C and (2) the radiant flux on unignited materials in the compartment or enclosure is approximately 20kW/meter2. (pp. 1-89)
TIME IT TAKES FOR FLASHOVER
What of the time it takes to produce flashover? According to Francis L. Brannigan, author of Building Construction for the Fire Service: “In 1980, the National Bureau of Standards [now the National Institute of Standards and Technology (NIST)] conducted fire tests of typical residential basement recreation rooms. The word `basement` could easily be dropped from this description as immaterial. The room could be a living room, a motel room, a fire station`s recreation room, a doctor`s office/reception area, or an elevator lobby in a hotel …. In less than four minutes, heavy flame was pouring out the full height of the doorway. Six minutes after ignition, the average gas temperature was reported as 7007C.”6
Custer, who also served as technical director for the movie Fire Power, reports that the fire documented within a living room of a single-family dwelling took only three minutes and 41 seconds from first flame to the time of flashover.7
An article with no byline in the August 1986 edition of Fire Command magazine noted that in the making of the NFPA movie Fire: Countdown to Disaster, flashover occurs within a bedroom in two minutes and 12 seconds from first ignition.
RESOURCES NEEDED
A fire department must focus on time if it is to respond in time to apply extinguishing agent on the burning material before the critical point at which the fire becomes deadly. “From the moment of ignition, to the moment it [the fire] goes out, there is a continuum of time,” observes Rexford Wilson.8 He describes the nine steps from ignition to extinguishment:
free burn,
permitted burn,
notification,
alarm processing,
turn-out,
travel,
setup and agent application,
combat, and
extinguishment.
To calculate our interdiction time, we must calculate the following:
the time it takes for the alarm to arrive at the central station alarm processing, plus
the time it takes for the emergency service`s dispatching center to handle the alarm and dispatch the fire department, plus
the time it takes for the fire department to mobilize and hit the street with a piece of fire apparatus, plus
the time it takes to travel to the scene of the emergency, plus
the time it takes from arrival at the fire scene to set up an attack and apply water to the burning material.
Most of these times are for the most part fixed. With the exception of travel times, these times should not vary considerably. The key to the issue should be travel time, which is a direct function of travel distance.
According to Paige Neiman, director of operations for SpectaGuard,9 an alarm company in Southeastern Pennsylvania, an alarm from a directly connected alarm system will take approximately 15 seconds to arrive at the central station. The central station operator then takes about 30 seconds to contact the local emergency services dispatch agency. This totals 45 seconds for the emergency service`s dispatching center to receive the alarm once it has been tripped.
Dispatching would be the next step in the continuum. The results of a survey of 57 fire agencies that protect a population of 11.4 million people revealed the times given in “Alarms Reviewed” on page 108. A total of 271,402 alarms were reviewed for dispatching and 91,027 runs for turn-out.10
TRAVEL TIMES
Jack Hausner, working for the Rand Institute under contract for the Office of Policy Development and Research, Department of Housing and Urban Development, provides mathematical equations concerning travel times as a function of distance.11 In these equations, travel time is expressed as “T” and distance is expressed as “D.”
T = 1.93D where D < .32 miles
T = .55 + 1.71D where D .32 miles.
As an example, if we desired our travel time to be 10 minutes, our travel distance would need to be no more than 5.52 miles. If we desired to have our travel time be one minute, our travel distance would need to be no more than .7 miles.
Hausner also provided a method for calculating the number of stations needed in a given area as a function of travel distance. In this calculation, travel distance is expressed as D, the area under consideration expressed as A, and the number of stations expressed as N. The equation: D = A/N.
Using the results of our previous equations and Upper Merion Township`s 16.8 square miles as the area studied, the fire department would need 10 stations if it wanted to have a travel time of no greater than one minute; we have four at present.
TIME/MOTION STUDY
To determine the current and proposed standards, descriptive research methods were used. To ascertain the time it takes for set-up and agent application, a limited time/motion study was conducted. This exercise was meant to determine the time expended from the arrival of the fire apparatus on-scene to agent application.
The study was conducted at the Haverford Township Fire Training grounds on a warm, dry evening during the Fall of 1998. Using a crew of four (driver/operator, officer, and two firefighters) and a 1991 model engine with preconnected 134-inch attack lines, the following scenario was followed:
l. The apparatus was driven up to the training tower, stopped 35 feet from the door. This distance approximated the average front yard setback for a single-family dwelling in Upper Merion Township. The stopwatch was started when the max-brakes were applied.
2. The crew, in full turnout gear but not wearing SCBA masks, disembarked the apparatus and dragged the attack line to the front door of the building.
3. After the entire hoseload of attack line was removed from its bed, the operator charged the line.
4. The attack crew, now standing at the door to the building, donned SCBA masks, bled the air out of the attack line, and advanced into the building and up the interior stairs.
5. When the hose stream was observed from the second-floor window of the building, the exercise was terminated.
This scenario was repeated six times, and the resulting times were recorded. The times for each repetition were within seven seconds of each other and averaged 98 seconds.12
RESULTS
What would it take for the fire department to respond in such a manner as to be able to apply extinguishing agent on the burning material prior to the point at which the fire becomes deadly? I came to the conclusion that it would be nearly impossible for the fire department to achieve a goal of applying an extinguishing agent on a fire before flashover. As Brannigan reported, “… in less than 4 minutes, heavy flame was pouring out the full height of the doorway.”13 This certainly describes a fire that has reached flashover. As Custer reported, the bedroom fire in the movie Fire Power reached flashover in three minutes and 41 seconds. In the movie Fire: Countdown to Disaster, flashover occurred in two minutes 12 seconds. If we averaged these times, we would find that flashover can occur in approximately three minutes and 18 seconds.
Without including travel time, we are already looking at 4.6 minutes for staffed departments and 6.6 minutes for departments without full-time staff. And, this is assuming that the smoke detector activated within 30 seconds of ignition.
FLASHOVER PREVENTION SYSTEM
“Prior to flashover, a fire can be extinguished with relative ease, and damage will be minor, but extinction of a post-flashover fire requires major resources and will be accompanied by major damage, if not the complete destruction of the contents and combustible.”14
Allen Ratzloff observes: “… it is virtually impossible for us to respond fast enough to prevent flashover. Therefore, a change in focus is in order.”15
It appears, therefore, that what is needed is a flashover prevention system. Bill Manning, editor of Fire Engineering, observes that “Flashover is what happens when people build boxes out of wood or brick or whatever and cram them full of furniture and furnishings that burn hot and fast when exposed to the heat of the fire.”16 He then goes on to suggest that the fire service educate the public about fire-retardant and flame-resistant home products.
Has this tactic worked? Look at your own homes. The contents are combustible, as is probably the structure itself. We have made little progress in this regard in the past eight years.
RESIDENTIAL SPRINKLERS: THE ANSWER
A rhetorical question: Has the fire service reached the point where today`s fire losses are deemed acceptable? Yet, when we compare our response times–4.6 minutes in staffed departments and 6.6 minutes in unstaffed departments–not including travel times, with the 3.3 minutes it takes for flashover, it becomes obvious that we need to reassess our approach to fire response. It appears that our traditional approach to fire safety has worked but only on a limited basis. New directions are needed, or are they?
Residential sprinklers can be the flashover prevention system needed to attempt to mitigate our fire problem. But where is the support for such systems?
In 1996, the International Fire Chiefs Foundation sponsored the Wingspread IV conference, at which an attempt was made to wake up the American fire service to provide the leadership needed: “It must be the responsibility of the American Fire Service to embrace the technological advances in fire detection, alarm and built-in suppression systems …. The fire service must support the adoption of codes and standards that mandate the use of detection, alarm, and automatic sprinkler systems, with a special focus on residential properties …. The fire service must reach to others to expand the circle of support to ensure that the goals of fire and accident prevention are reached.”17
RECOMMENDATIONS
At the outset of this project, I was attempting to determine what it would take to have the fire department make a difference in responding to a fire to save most of the 5,000 or so people dying in fires each year in this country. I found that, given the resources at hand, we probably can`t. If we really want to address this fire problem, we must become involved with other organizations. The time has come for us to recognize that we have come as far as we can alone and with our present resources. We must join with groups such as the International City Managers Association, the International Code Council, the American Home Builders Association, the Building Officers and Managers Association, the Insurance Services Office, and the various fire service associations to promote the installation of automatic sprinklers in residential structures, including one- and two-family homes. In fact, the installation of residential sprinklers should be the rule instead of the exception.
Upper Merion Township has been aware of these issues for many years. Since 1987, all nonresidential construction larger than 2,000 square feet must be protected with automatic sprinklers. Beginning in 1988, all new homes have been required to be sprinklered regardless of square footage. n
Endnotes
1. National Fire Protection Association`s Fire Analysis and Research Department, personal communication, Kimberly Rohr, Feb. 2, 1998.
2. America Burning Revisited, U.S. Fire Administration, Washington, D.C., 22.
3. Milke, James. Fire Dynamics. (Lexington, Mass.: Ginn Custom Publishing, 1984), 8-2.
4. Bukowski, Richard and Richard Peacock. 1995. Defining Flashover for Fire Hazard Calculations. National Institute of Standards and Technology, Gaithersburg, Md., 82.
5. Lie, T.T, “Effects of Energy Conservation in Buildings,” In Fire Protection Handbook, A. Cote, ed., National Fire Protection Association, Quincy, Mass., 4-205.
6. Brannigan, Francis L. 1992. Building Construction for the Fire Service, third edition. (Quincy, Mass.: National Fire Protection Association), 404.
7. Custer, Richard, “Fire Power: Making the Movie,” Fire Journal, 1986; 80:6, 23-26.
8. Wilson, Rexford. 1994. Nine Steps from Ignition to Extinguishment. (Putney, Vt.: Firepro), 2-3.
9. Personal communication, Sept. 1998.
10. “IAFC Accreditation Committee surveys fire departments, charts response times,” Charles Rule, IAFC On-Scene. 1998; 6:16, 7-8.
11. Hausner, Jack. Determining the Travel Characteristics of Emergency Service Vehicles. (New York, N.Y.: Rand Institute, 1975), 93.
12. Thanks to Chief Kevin Kramer, Deputy Chief Sam Berry, and the crew of the Bon Air Fire Company, Haverford Township Fire Department, for their assistance.
13. Brannigan, 404.
14. Drysdale, Dougal. “The Flashover Phenomenon. Fire Engineers Journal, 1996; 56:185, 18-23.
15. Ratzloff, Allen. Time to Flashover–Implications for Strategic Planning. National Fire Academy, Emmitsburg, Md., 1992, 4.
16. “The Flashover Phenomenon,” William Manning, Fire Engineering. 1990; 143:11,6.
17. Wingspread IV Statements of Critical Issues to the Fire and Emergency Services in the United States, International Fire Chiefs Foundation, Sterling, Va., 1996, 10-11.
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n JOHN R. WATERS is chief fire marshal and director of safety and codes enforcement for Upper Merion Township, King of Prussia, Pennsylvania. Previously, he was fire protection specialist for the Albert Einstein Medical Center in Philadelphia and a career firefighter for the Lower Merion Fire Department in Ardmore, Pennsylvania, where he served as driver/operator. He is a senior instructor at the Pennsylvania Fire Academy and formerly served as an adjunct instructor at the Delaware County Community College and the Emergency Management Institute. He has a bachelor`s degree in fire science from the University of Maryland, College Park, and is working toward a master`s in public safety at St. Joseph`s University in Philadelphia. He is currently enrolled in the National Fire Academy`s Executive Fire Officer Program.
