Fire extinguishers – Processes – Of extinguishing fire
Reexamination Certificate
2000-11-21
2002-06-11
Douglas, Lisa A. (Department: 3752)
Fire extinguishers
Processes
Of extinguishing fire
C169S047000
Reexamination Certificate
active
06401830
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of extinguishing fires. Particularly, the present invention relates to a method of extinguishing fires. More particularly, the present invention relates to a method of extinguishing fires using a clean fire extinguishing agent. More particularly, the present invention relates to a method of extinguishing fires that has no adverse effects on the environment and does not risk the health and safety of humans.
2. Description of the Prior Art
In order for a fire to occur there are four requirements that must be met. These requirements are (1) suitable fuel, which is any material that can be easily oxidized, (2) a suitable oxidizing agent, (3) a source of heat, and (4) a chemical chain reaction path. Considering these four requirements for a fire there are basically four ways to extinguish a fire. These four methods of extinguishing a fire are (1) to remove heat, (2) to separate the fuel from the oxidizer, (3) to dilute the fuel/oxidizer concentration, and (4) terminate the chemical chain reaction. There are different compounds that are used for each of these extinguishing methods. Water is used for heat removal. High expansion foam may be used for separating the fuel from the oxidizer. Halon can be used to terminate the chemical chain reaction. Finally, gaseous carbon dioxide (CO
2
) or gaseous nitrogen (N
2
) can be used to dilute the fuel/oxidizer concentration.
Fires and combustion occur not only in buildings and residences but also in the wild. Forest fires occur at a large rate in the United States. Recently, there have been over 300 forest fires recorded in the United States and the fires have spanned over 55,000 acres of land. Forest fires are extremely costly to extinguish using the present fire fighting methods. For instance, one fire that occurred in the Valley Complex of Montana required 4.9 million dollars to extinguish. The main concern of fire engineers has been to create a clean fire extinguishing agent that has sufficient fire suppression properties but does not have harmful effects to human health or the environment.
Several methods of extinguishing fires have been developed using various fire extinguishing agents. Halon 1301 has been relied on in recent years as a clean agent fire suppression medium that has no significant threat to life. The problem with Halon 1301 is that it is a chlorfluorocarbon and it is associated with the destruction of the ozone layer. There has been a recent urge to discover materials that have similar fire suppression properties to Halon just without the harmful environmental effects.
Several traditional agents are being used to replace the use of Halon 1301. Gaseous CO
2
is an example of such an agent because CO
2
has cooling and oxygen depleting properties. In enclosed areas, CO
2
safety features must be added to the system to prevent CO
2
discharge while an area is still occupied by people.
Another traditional method is to use wet systems like sprinklers. These wet systems are not very suitable for areas that contain electrical equipment. Another problem with wet systems is that long before there is enough heat to activate the wet system there will be a large amount of smoke accumulation and smoke will damage equipment in the area. There are two wet systems in particular that are being used in replace of Halon 1301.
The first of these two wet systems is a fine water spray system. There are various systems that are available and these systems vary in several aspects including water pressure and whether or not the water is pure or mixed with other elements. The water in these systems can also be de-ionized which will reduce the risk of electric shock and it can be used around electrical equipment. Unlike traditional wet systems, only a small amount of water is needed to put out a fire and because the water system is activated by smoke detectors. This minimizes the amount of damage caused by combustion emissions.
The second of the two wet systems is high expansion foam. The foam consists of masses of bubbles which cover a fire and prevent any air from fueling the fire. The heat from the fire causes the foam to vaporize the water content into steam. This process has the effect of absorbing heat. The steam and air that are now surrounding the fire has an oxygen content of only 7.5% which is not enough oxygen for combustion to occur. Finally, the bursting of the bubbles results in the contents of the bubbles being deposited on hot surfaces and in turn the bubbles cool down these hot surfaces.
Another alternative agent is HCFC Blend “A”, or more commonly NAF S-III. This agent is a blend of HCFCs 22,123 and 124 and has a detoxifying agent added to it to minimize the amount of post combustion products. NAF S-III qualifies as a clean agent because it does not conduct electricity and it does not leave residue after evaporation. The problem with this material is that the production of HCFCs is scheduled to cease in 2030. Also, use controls are being installed to ensure that HCFCs are not used in place of environmentally sound alternatives.
Heptafluoropropane, or FM-200, is currently the only halocarbon with an ozone depleting potential of zero which can be used as a fire extinguishing agent. This agent does not conduct electricity and does not leave a residue after evaporation, so it is also a clean agent. FM-200 has been approved by the EPA for use in normally occupied spaces. One problem with this agent is that it can produce post combustion products in greater amounts than Halon when it comes into contact with flames or heat.
There are also several inert gas blends that are being used to extinguish fires. Two of these nitrogen based fire extinguishing agents are called INERGEN and Argonite. Both of these materials have fire extinguishing capabilities but do not harm the ozone layer at all. Inert gas blends are designed to reduce the level of oxygen in an environment from 21% to 14%. At 14% there is no longer enough oxygen to sustain combustion. Also, inert gas blends do not break down to produce harmful decomposition products while they are extinguishing a fire.
INERGEN contains 52% nitrogen, 40% argon and 8% CO
2
. INERGEN can be used in normally occupied spaces and has completed fire extinguishing tests. When INERGEN is discharged it creates an oxygen deficient environment. INERGEN contains CO
2
to promote breathing characteristics. There is also no fear of toxicity from INERGEN.
Argonite does not contain any CO
2
, just 50% nitrogen and 50% argon. There are indications that healthy people may be exposed to oxygen levels of 12 to 14% for short periods of time without having any effect on mental capacity. Therefore, the supporters of Argonite do not see any need for adding CO
2
to the mixture. Argonite is a colorless, odorless gas so an odorizer is sometimes added to alert personnel of a leakage or discharge.
When selecting a fire extinguishing system there are several factors to consider. One of these factors relates to the environment. There are many environmental aspects to consider and the agent that is chosen should minimize the amount of harm done to the environment.
Therefore, what is needed is a fire extinguishing agent that has the capabilities to suppress combustion. What is further needed is a fire extinguishing agent that does not conduct electricity and does not leave a residue after evaporation so it will be categorized as a clean agent. What is still further needed is a fire extinguishing agent that has minimal adverse effects on the environment and does not destroy the ozone layer. What is still further needed is a fire extinguishing agent that has no hazardous decomposition products and poses no threat to the safety and health of humans. Finally, what is still further needed is a fire extinguishing system that is both cost effective to initiate and to maintain.
SUMMARY OF THE INVENTION
It is an object of this present invention to provide a fire extinguishing agent that has sufficient fire suppression capabilities. It is a f
Deleault, Esq. Robert R.
Douglas Lisa A.
Mesmer & Deleault, PLLC
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