That is correct. Some wristwatches contain several tritium vials on the hands plus numbers. Current watches contain less than 25 microcuries of tritium, and that's the sum of several tritium vials.
http://www.luminox.com/
A single typical-size tritium vial would therefore contain less than 25 microcuries (25 uCi)
Tritium emits only beta radiation which is stopped by your skin or the air itself. E.g, the max range in air is only 0.15 inches.
Tritium is therefore only a danger if inhaled or ingested. So what if you broke a tritium vial?
The maximum occupational human health exposure for inhaled or ingested tritium is 80 MILLIcuries per year, or 3,200 times the tritium in ALL the vials of a watch.
Therefore you'd have to break MANY THOUSAND tritium vials right under your nose while simultaneously inhaling to even approach this limit.
http://bfa.sdsu.edu/ehs/radch10.htm
There is a generally accepted relationship between ingested tritium and absorbed radiation:
Committed Effective Dose Equivalent (CEDE) in soft tissue is 64 mrem per millicurie (mCi) ingested.
So radiation absorbed from breaking and inhaling 100% of the tritium in approx 5 vials (total 25 microcuries, the amt in a watch) is:
64 mrem * 1 millicurie/25 microcuries = 1.6 millirem
http://www.physics.isu.edu/radinf/tritium.htm
There are MUCH greater common radiation risks than tritium vials.
A single cross-country airline flight (depending on solar activity) can potentially expose you to 100 millirems, 62 TIMES the amount from breaking and inhaling 100% of the tritium in 5 vials.
The average radiation exposure from household radon gas is 100-200 mrem/year and in some cases 600 mrem/year. So just living in a house ONE YEAR with a high radon level can expose you to 375 TIMES the radiation of breaking and inhaling 100% of the tritium in 5 vials.
If you're concerned about radiation don't worry about inhaling tritium from broken vials -- get a household radon test. You can get one at Lowe's for $16.00.
