>I have a tritium based keyring at home!  You can buy these freely from e.g.
> http://www.theglowcompany.co.uk/acatalog/GLOW_RINGS.html

OK.

>The guy I work next to is keen on diving, and bought a couple of
>these keyrings to fit the small glass vials they contain into his
>wrist mounted dive computer display.
>
>Would be interesting to know how much radiation these things
>give off, but it must be pretty low.  I hope.

I figured so too at the time, but this was around 1980, and I guess the fear
then was of useful items falling into enemy hands ... I can't specifically
remember what the radioactive source was, but seem to recall it was tritium.
I know we had to shut ourselves in the safe that was used as an anechoic
chamber and allow our eyes to accustom to the darkness for quite some time
before you could see the pale glow these gave.

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