Note: Descriptions are shown in the official language in which they were submitted.
20~7~
BACKG~OUND OF T~E INVENTION
Field of the Invention. This invention relates to fire
extirlguishing methods utiliziny l-Chloro-1,1,2,2-
tetrafluoroethane, HCF2CF2Cl.
Descri~tion of the Prio{ Art. The use of certain
bromine, chlorine and iodine-containing halogenated
chemical agents for the extinguishment of fires is common.
These agents are in general thought to be effective due
to their interference with the normal chain reactions
responsible for flame propagation. It is taught in the
art that the effectiveness of the halogens is in the order
I > Br > Cl > F, for example, C.L. Ford, in Halo~enated Fire
u~ressants, R.G. Gann, ed., ~CS Symposium Series 16.
The use of iodine-containing compounds as fire
extinguishing agents has been avoided primarily due to the
expense of their manufacture or due to toxicity
considerations. The three fire extinguishing agents
presently in common use are all bromine-containing compounds,
bromotrifluoromethane (CF3Br), bromochlorodifluoromethane
(CF2~rCl), and dibromotetrafluoroethane (BrCF2CF2~r). It has
generally been taught that to be effective as a fire
extinguishing agent, a molecule would have to contain
bromine, although certain chlorine-containing compounds have
been proposed as extinguishing agents, for example
chloropentafluoroethane (CF:3CF2Cl) as described in US Patent
3,~44,354 to Larsen.
~ lthough the above name~ bromine or chlorine-containing
agents are effective in extinc~uishing fires, totally
halogenated agents such as CF3Br, CF2BrCl and CF3CF2Cl
,
..
- ` ~
.
2 Q ~'7 ~
containing bromine or chlorine are asserted by some to be
capable of the destruction of the earth's protective ozone
layer.
It is therefore an object of this invention to provide a
5 method for extinguishing fires that e~tinguishes fires as
rapidly and effectively as the present employed agents, and
is environmentally safe with respect to ozone depletion.
2Q~78~0
SUMMARY OF THE INVENTION
The foregoing and other objects, advantages and features
of the present invention may be achieved by employing
l-chloro-1,1,2,2-tetrafluoroethane (HCF2CF2Cl) and blends
thereof with other compounds as fire extinguishants for use
in fire extinguishing methods and apparatus. More
particularly, the method of this invention involves
introducing to a fire l-chloro-1,1,2,2-tetrafluoroethane in a
fire extinguishing concentration and maintaining such
concentration until the fire is extinguished.
l-Chloro-1,1,2,2-tetxafluoroethane may be used alone or in
admixture with other compounds, optionally in the presence of
a propellant. Generally l-chloro-1,1,2,2-tetra-fluoroethane
or its mixtures with other compounds are employed in the
range of about 2 to 15%, preferably 4 to 10%, on a v/v basis.
.
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20478~
~4--
~ESCRIPTION OF T~E PREFERRED EMBODIMENTS
In acc~rdance with the present invention,l-chloro-1,1,2,2-tetrafluoroethane has been found to be an
effective fire extinguishing agent at concentrations safe for
use. However, because l-chloro-1,1,2,2-tetrafluoroethane
contains a hydrogen atom, it has a very low ozone depletion
potential due to its removal in the troposphere via reaction
with hydro~yl radicals. For example, employing the method of
Ba~son for the estimation of ozone depletion (ODP) values,
1-chloro-1,1,2,2-tetrafluoroethane has an ODP of 0.03,
compared to ODP values of 19.26 and 2.65 for the presently
employed agents CF3Br and CF2BrCl, respectively, a reduction
in ODP of greater than 99% in each case.
l-Chloro-1,1,2,2-tetrafluoroethane has an LC50 value (con-
centration necessary to cause death in half of test subjects)of 21~ v/v as reported in Simons, ~_uorine Chemist~y, volume
3, and is hence effective at concentrations well below levels
harmful to living things.
l-Chloro-1,1,2,2-tetrafluoroethane may be used alone or
in admixture with other compounds, optionally in the presence
of a propellant. Among the compounds with which
l-chloro-1,1,2,2-tetrafluoroethane may be blended are
chlorine and/or bromine containing compounds such as CF3Br,
CF2BrCl, CF3CF2Cl, and BrCF2CF2Ur. Other compounds forming
25 useful blends with 1-chloro-1,1,2,2-tetrafluoroethane include
CFZHBr, CF3CIIFBr, CF3CF2l~, CF3CIIFCF3, CF3C~FCl, CF3CHC12,
CF4, CF3~, and similar fluorocarbons. The materials of this
invention may also be used in the presence of a propellant,
such as N2, C02 or Ar.
Where l-chloro-1,1,2,2-tetrafluoroethane is employed in
blends, it is desirably at a level of at least about 5
percent by weight of the blend. l-Chloro-
1,1,2,2-tetrafluoroethane is preferably employed at high
enough levels in such blends so as to minimize the adverse
20~7~0~
environmental effects of chlorine and bromine containing
compounds.
l-Chloro-1,1,2,2-tetrafluoroethane may be effectively
employed at substantially any minimum concentration at which
the fire may be e~tinguished, the exact minimum level being
dependent on the particular combustible material, and the
combustion conditions. In general, best results are achieved
where l-chloro-1,1,2,2-tetrafluoroethane or mixtures and
blends are employed at a level of about 4% (v/v). Likewise
the maximum amount to be employed will be governed by matters
o~ economics and potential to~icity to living things. About
15~ provides a convenient maximum for use of 1-chloro-1,1,2,2-
tetrafluoroethane and its mixtures thereof in occupied
areas. Concentrations above 15% may be employed in
non-occupied areas, with the e~act level determined by the
particular combustible material and the conditions of
combustion.
l-Chloro-1,1,2,2-tetrafluoroethane may be applied using
conventional application techniques and methods used for
agents such as CF3Br and CF2BrCl. Thus, the agents may be
used in total flooding systems, portable systems or
specialized systems. Thus, as is known to those skilled in
the art, l-chloro-1,1,2,2-tetra~luoroethane may be
pressurized with nitrogell or other inert gas at up to about
600 psig at ambient condition5
Practice of the present invention is illustrated by the
following e~amples, which are presented for purposes of
illustration but not of limitatiorl.
2~7~0
--6--
EXAMPLE 1
Concentrations of agent required to extinguish diffusion
flames of n-heptane were determined using the cup burner
method. Agent vapor was mixed with air and introduced to the
flame, with the agent concentration being slowly increased
until the flow was just sufficient to cause extinction of the
flame. The data are reported in Table 1, which demonstrate
the effectiveness HCF2CF2Cl. Values for CF3Br and CF2BrCl
are included for reference purposes.
Table 1:
Extinguishment of n-heptane Diffusion Flames
_______________________________________________________________
~gent Air flow ~gent Required Extinguishing Conc.
cc/min cc/min % v/v mg/L
_______________________________________________________________
HCF2CF2C1 16,200 1290 7.4 411
CF2BrC1 16,200 546 3.3 222
CF3Br 16,200 510 3.1 189
_______________________________________________________________
~ ,L~E_2
The procedure o~ example 1 was repeated employing
n-~utane as fuel. ~esults are sllown in Table 2, and
20 demonstrate tlle eicacy o IICF2CF2Cl for extinguishment of
fires.
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Table 2
Extinguishment of n-Butane Diffusion Flames
_______________________________________________________________
Agent Air flow Agent required Extinguishing Conc.
cc/min cc/min % v/v mg/L
_______________________________________________________________
HCF2CF2C1 16,200 1158 6.7 372
CF2BrC1 16,200 420 2.5 168
CF3Br 16,200 396 2.4 146
_______________________________________________________________
While the bromine or chlorine containing agents CF3Br and
CF2BrCl are somewhat more effective than HCF2CF2Cl, the use
oE HCF2CF2Cl in accordance with this invention remains highly
effective and its use avoids the significant environmental
handicaps encountered with totally halogenated agents.
