Re: H-3 in "EXIT" Signs

[Schoenhofer <schoenho@via.at>]

At 11:46 10.02.1997 -0600, you wrote:
>Can anyone tell me the form of H-3 used in these self-luminescent EXIT
>signs.  I seem to remember someone saying (a long time ago) that the H-3
>was in a "solid, non-dispersable form" so that it would pose no
>contamination hazard if one of the signs were ever broken up.  But,
>recently I thought someone on RADSAFE mentioned H-3 gas in connection
>with the EXIT signs.  If it is H-3 gas, what reasoning is used to
>justify general licensing for these devices (assuming that the signs
>could be ruptured and the gas released).
>
>Thanks,
>Chris Hogan
>chogan@colan.uams.edu
>or 
>cchogan@life.uams.edu
> ----------------------------------------------------------

Chris,

Yes, you remember correctly. According to my information the ones used in
airplanes should contain tritiated plastic as is normally used in luminous
dials of watches. I distributed this on radsafe and got an answer that the
exit signs actually contain tritium in sealed glass tubes - the way it is
used in another type of luminous dials. 

I cannot confirm either version, but the glass tube version seems to me to
be more likely. By now I have good reason to believe that the exit-signs in
the Austrian Airlines airplanes contain tritium in glass tubes. This is
because they have difficulties to dispose of them. 

Personally I think that sealed glass tubes make more sense. From tritiated
polystyrene, which is used in luminous dials, about 5 % of the content will
be liberated each year, which would mean that there will be a more or less
constant contamination. Glass tubes or capillaries are not considered to be
broken at random, but only in the case of an accident, which is much less
likely to occur. In my opinion the potential exposure from breaking a
capillary is in relation to the benifit of safe guidance to an emergency
exit in case of an accidence negligible. 

Franz 
Schoenhofer
Habichergasse 31/7
A-1160 WIEN
AUSTRIA/EUROPE
Tel./Fax:	+43-1-4955308
Tel.:		+43-664-3380333
e-mail:		schoenho@via.at