11.3.3. At what temperature does a typical fire burn?
The duration and the maximum temperature of a fire in a building compartment depends on several factors including the amount and configuration of available combustibles, ventilation conditions, properties of the compartment enclosure, weather conditions, etc. In common circumstances, the maximum temperature of a fully developed building fire will rarely exceed 1800°F (982°C). The average gas temperature in a fully developed fire is not likely to reach 1500°F (816°C). Temperatures of fires that have not developed to post- flashover stage will not exceed 1000°F (538°C). aisc.org
Wood and gasoline burn at essentially the same flame temperature. The flame temperatures achieved by all hydrocarbon fuels (plastics and ignitable liquids) and cellulosic fuels are approximately the same, although the fuels release heat at different rates ( NFPA 921 , 4-8.1). atslab.com
There is no indication that any of the fires in the World Trade Center buildings were hot enough to melt the steel framework. Jonathan Barnett, professor of fire protection engineering, has repeatedly reminded the public that steel - which has a melting point of 2,800 degrees Fahrenheit - may weaken and bend, but does not melt during an ordinary office fire. wpi.edu
From the FEMA Report:
A.3.1.3 Response of High-rise, Steel-frame Buildings in Previous Fire Incidents:
In recent years, three notable fires have occurred in steel frame buildings, though none involved the total floor area as in WTC 1 and WTC 2. However, prior to September 11, 2001, no protected steel frame buildings had been known to collapse due to fire. These previous three fire incidents include the following:
- [1st Interstate Bank Building, Los Angeles 1st Interstate Bank Building, Los Angeles, May 4-5, 1988]
- [Broadgate Phase 8, UK Broadgate Phase 8, UK, 1990]
- [One Meridian Plaza, Philadelphia One Meridian Plaza, Philadelphia, February 23-24, 1991]
In the case of the fire at One Meridian Plaza, the fire burned uncontrolled for the first 11 hours and lasted 19 hours. Contents from nine floors were completely consumed in the fire. In addition to these experiences in fire incidents, as a result of the Broadgate fire, British Steel and the Building Research Establishment performed a series of six experiments at Cardington in the mid-1990s to investigate the behavior of steel frame buildings. These experiments were conducted in a simulated, eight-story building. Secondary steel beams were not protected. Despite the temperature of the steel beam reaching 800-900 degrees Centigrade (1,500-1,700 degrees Fahrenheit) in three tests (well above the traditionally assumed critical temperature of 600 degrees Centigrade [1,100 degrees Fahrenheit]), no collapse was observed in any of the six experiments.
One important aspect of these previous incidents is that the columns remained intact and sustained their load carrying ability throughout the fire incidents (though there was no structural damage caused by impacts). Throughout the fire in One Meridian Plaza, horizontal forces were exerted on the columns by the girders and despite the 24 to 36-inch deflections of the girders, floor beams, and concrete and steel deck floor slabs, the columns continued to stabilize the building throughout the fire and for several years after the fire.
[Parque Central Caracas, Venezuela Oct 17, 2004 Parque Central Caracas, Venezuela]
[1st Interstate Bank Building, Los Angeles May 4-5, 1988 1st Interstate Bank Building, Los Angeles]
[One Meridian Plaza, Philadelphia Feb 23, 1991 One Meridian Plaza, Philadelphia]
[World Financial Center, Shanghai Aug 14, 2007 World Financial Center, Shanghai]
[Deutsche Bank Fire 8-18-07 August 18, 2007 Deutsche Bank Fire]
[Brazillian Skyscraper Fire February 15, 1981 Brazillian Skyscraper Fire]
Churchill Plaza, Basingstoke following the fire.
"The presence of melted metals at floor level is particularly meaningless in the context of a black hole fire. A study of the 1991 Oakland fire that burned 3,000 homes revealed the presence of melted copper ( [Melting and Boiling points 1083C] ) in over 80% of the burned structures, and what appeared to be melted steel in over 90% of the burned structures. With respect to steel, looks can be deceiving. What appears to be melted may be merely oxidized. Interpret melted metals, particularly steel, with caution, and interpret the temperatures you infer from these melted metals with extreme caution. High temperatures are more likely a result of increased ventilation than of the presence of ignitable liquid residues." atslab.com
"Most of us expect to find melted aluminum ( [Melting and Boiling points 660C] ) at just about any fire scene, and the finding of melted copper ( [Melting and Boiling points 1083C] ) is also reasonably common." atslab.com
"Normal unaccelerated house fires can and do achieve temperatures sufficiently high to melt copper ( [Melting and Boiling points 1083C] )." atslab.com
"The theoritical flame temperature which can be achieved by hydrocarbon liquids is listed in the Fire Protection Handbook at between 3500F and 4200F. Thus, flammable and combustible liquids are cited in an "athorative" source as having enough energy melt steel. The temperatures in the handbook, however, are for ideal flames , which are never achieved in a real fire. We have a shortage of oxygen, rather than an abundance of it, and the likely flame temperatures are below 2000F." atslab.com
"When exposed to a fire, steel bedsprings will undergo four distinct changes, as the temperature increases. Unfortunately, only the first two changes are likely to be detectable by visual observation. Figure 2 shows the micro structure of a bedspring before it has been heated. The radically elongated grains are typical of spring steel. Upon exposure to elevated temperatures (up to 1300F), the spring will anneal and loose most of it's residual tension, as a result of stress relief, as shown in Figure 3. After exposure to temperatures over about 1300F, the grains of steel actually recrystallize, and the micro structure shown in Figure 4 is typical. A heavy oxidation scale will usually be present on steel which has been exposed to temperatures sufficiently high to cause recrystallization. At even higher temperatures, decarbonization (loss of carbon) of the steel occurs, and the micro structure shown in Figure 5 may be expected. This micro structure was obtained after heating at 1800F for two and one half hours. Finally when the melting point of steel is reached (somewhere between 2200F and 2400F depending on the alloy), incipient melting begins in the grain boundaries. The resolidified melted material, such as that shown in Figure 1, can be identified. Oxidation will frequently result in the formation of a stable oxide coating." atslab.com
On Stop Shop in Structural Fire Engineering on the Madrid Spain Windsor Tower fire. http://www.mace.manchester.ac.uk/project/research/structures/strucfire/CaseStudy/HistoricFires/BuildingFires/default.htm