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DISCUSSION
Generally, the precise limits of effectiveness of avalanche
balloons have not yet been determined. To mention some
factors:terraincharacteristics(terraintraps),largeava-
lanches, wet snow conditions, risk of injuries have not yet
been considered.
*The balloon only appears to be effective as long as the
unit consisting of the victimand the balloon can flow
along with the avalanchesnow. When the unit and its
surrounding snow come to rest,in particularin a ter-
rain trap, the victim and the balloon still may get com-
pletely buried by further avalanche snow.
*Inmanycasesvictimswithinflatedballoonswillbe
carried further by the avalanche than victims without
avalanche balloon.Theconsequences depend onthe
terrain.
*During avalancheaction and after standstill of the ava-
lanche the balloon is frequently located well above the
victim. It is likely that the victim will be buriedin prone
position.
*Some of the results may be product specific.
*Itisnotfullyclearhowand/orunderwhich circum-
stances the proposed theoretical mechanisms contrib-
ute to the observed effect of the avalancheballoon.
These questions will be subjects foran extended study in
1996-99 at SFISAR.
However,ineverysingle case ofwhich we know,the
balloon was not completely buried and hencerepresented
a good marker for the immediate rescue by other members
of the party.
Finally,while the avalanche balloon has to be consid-
ered as a technical device that can reduce the risk of ava-
lanche burial, it is at least as important to take precautions
to reduce the risk of being caughtin an avalanche.
REFERENCES
deQuervain,M.1975.Basicquestions regardingthedetec-
tion of victims covered by an avalanche. In: Avalanches - pro-
tection,location,rescue.ProceedingsoftheSymposiumof
theFondationInternationaleVanniEigenmanninSulden
(Italy),April26-30,1975.FondationInternationaleVanni
Eigenmann, Milano, Italy, 41-50.
Savage, S.B. 1993. Mechanics of granular flow. In: Hutter (Ed.),
Continuummechanics in
env ironmental sciences and geophysics. CISM Int. Centre for
Mechanical Sciences Ser.No. 337, 467-522.
Tschirky,F.,R.Meister,W. Ammann,O.Buser,W. Caviezel
and M. Hiller. 1995. Experimental investigations of the effec-
tivenessofavalancheballoons.In:Sivardiere,F.(Ed.),The
contribution of scientific research to safety with snow, ice and
avalanche,Proceedings,30March - 3June 1995,Chamonix,
France. ANENA Grenoble, France, 299-307.
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