Fire on the Web - Fire Safety on the Holidays
Please click on this link to view a video of what happens to a room when a Christmas tree catches on fire: http://www.fire.nist.gov/tree_fire.htm
According to the National Fire Protection Association statistics, between the years 1999 to 2002, there were on average 310 residential house fires per year caused by Christmas trees igniting. These fires resulted in14 deaths, 40 injuries, and 16 million dollars in damages per year.
The primary cause for the majority of these fires was a combination of dry trees and electrical arcing from lights, cords, and plugs. This article will explain some basic fire investigation terminology and demonstrate why Christmas trees can be so dangerous if not watered.
How can a Christmas tree cause so much destruction? One of the major reasons is that people routinely do not adequately water their trees on a regular basis. It has been proven that when a tree is watered on a regular basis, it is more difficult to ignite.
An average person does not understand the tremendous heat release rate of a dry Christmas tree. Heat release rate is defined in the 2004 edition of NFPA 921, Guide for Fire and Explosion Investigations as "the rate at which heat energy is generated by burning."
What this means to the layperson is that certain fuels, such as a dry Christmas tree, can burn very rapidly under certain conditions. Due to the tremendous heat release rate and the large amount of fuel from the tree and home furnishings, this can cause rapid-fire conditions, tremendous amounts of smoke, and the transfer of these byproducts to the other areas in a house.
Another thing that can happen due to the rapid heat release rate is what many in the fire investigation field call "flashover." Flashover is defined in the 2004 edition of NFPA 921 Guide for Fire and Explosion Investigations as "a transition phase in the in the development of a compartment fire in which surfaces exposed to thermal radiation reach ignition temperature more or less simultaneously and fire spreads rapidly throughout the space, resulting in full room involvement or total involvement of the compartment or enclosed space."
What this means to the layperson is that a fire in a room or compartment has basic stages where it grows from a small fire to a very large fire. It is later in the development of these stages that the fire reaches flashover or full room involvement. When this begins to occur, the temperatures at the ceiling level begin to reach 1100 degrees Fahrenheit. This heat begins to radiate throughout the room, which causes all the combustible materials in the room to ignite at one time. When this event occurs, temperatures in the room can rise to 1800 degrees Fahrenheit. The amazing thing is that this flashover event can occur in a matter of seconds.
The reason that flashover is so dangerous is that once flashover occurs in a room there is almost no chance of survivability either by a person inside the room or by a firefighter wearing protective clothing coming to rescue that person. This event can also cause the fire investigator trouble because once a room reaches flashover, it can cause major destruction to the room making the investigator's job in determining the origin and cause of a fire even more difficult.
At the top of this article is a link to a video that was part of a study conducted by the Building and Fire Research Laboratory Division of the National Institute Of Standards and Technology. In the video, it shows how a dry Scotch Christmas tree exposed to a small flame can rapidly burn. Towards the ending of the video, one can see the beginning stages of flashover.
http://www.fire.nist.gov/videotest/tree3202402web.avi
Hopefully this article helps the layperson understand the dangers of fire heat release rate and flashover. Furthermore, this article should act as a reminder for those who buy Christmas trees over the holidays to water your tree regularly and make sure your Christmas tree lights, cords, and plugs are operating in a safe manner.
Following is a link to the United States Fire Administration on holiday fire safety tips. http://www.usfa.fema.gov/safety/tips/holiday.shtm