It seems the number of watches with GTLS (Tritium) tubes appears to be on the rise, so I just wanted to provide a few points of clarification on some misconceptions. Those of us who are Ball watch fans have become well versed on some of the fine points around these tubes. I just want to pass along a few things that I have seen frequently misstated about the tubes and provide clarification. At first these were licenses to come into the US under a NRC license designation T-25. This is not a type of tube or size it is a licenses that allows for up to 25 mci of Tritium in total content in a watch . The actual watch may have any number between 0-25mci and it will still be license under T-25. A few years ago Ball Watch was the first to find a section in the regulations that allowed them to obtain a license for total Tritium content above 25 mci up to 100 mci. This was designated T. Apparently others (most likely mb Microtec the tube manufacturer) now have a similar license that is designated T-100. This is not a tube size it is a license for the total Tritium contents as stated above. As with the T-25 watches with a T or T-100 on the dial generally have varying total content. A watch with 25.1 mci of Tritium would still be a T or T-100 watch.

Statements that a watch has T-25, T or T-100 tubes are not correct. All three of these could have the same tubes, just the T or T-100 would have more of them. Lets's take the basic dive watch. It generally has 16 points that are luminous:

The pip (1)+ The dial markers (12)+ the 3 hands

In the interest of simplification let's say the markers are all the same size and we are at 100mci of total Tritium content. So if there are 16 equal sized tubes in this watch they would be 6.25mci each. If we change this to a T-25 watch with the full 25mci of Tritium then the tubes would be 1.56 mci of Tritium. In the real world the watches have varying tube sizes and do not go all the way to these limits. While it may be possible to make a 100mci tube, if a watch truly had a T-100 tube it would only have one and would be at the limit. That would not communicate much information in the dark. Manufactures do not state what these totals are for each watch so we can only go by which license they fall under. Ball did state at the launch of the EHC Spacemaster X-Lume (glow) that this watch comes as close as possible to the 100mci limit. This watch does this with 80 tubes. Watches that are using larger tubes generally are farther from the cut off since each tube uses a bigger chunk of the limit. In practice even the newer larger tubes are probably not larger than 3-5 mci each.

Green tubes are the brightest and red are generally the dimmest. The others fall somewhere in the middle.

Next let's talk about the half life fear. First thing is to understand that unlike the old Tritium paint the Tritium gas is just an exciter in this process. In the newer tubes the gas can be saturated to a point if specified by the company ordering the tubes. I do know this is the case for Ball, but others I do not have similar access to information. While there is a half life decay (Apx. 12.5 years) of the gas the visually perceived intensity is not reduced to half, but a value somewhere in the middle between full and half due to the saturation. The watch will still be very bright in the dark, and far more visible than conventional lume after an hour. Then at the second half life period the intensity will be just above 1/4 of new, but still highly visible. Thus the reason for Ball's and a few other greater than 25 year claim. Some manufactures may be using lesser tubes so they may not do as well. This life is comparable to conventional lume where the binder is the weak link and actually the manufacturer claims a bit less life than the tubes.

Ball watch is the only GTLS watch company that has said anything about replacement. Probably since every watch they make uses this technology. Ball's estimate for tube replacement falls in line with the cost to have a decent pro relume a similar conventional lume watch. Remember that the disassembly of the watch to get to the dial and hands has to be factored into the cost. I know of people who have had tubes replace both in and out of warranty by Ball. The cost varied based on the watch, but it appeared to be $10-20 per tube depending on size. Do not hold that as a hard figure, and like everything else cost go up over time.

Last to address safety or the actual chemical and electrical interaction that makes these work. Ball has an excellent technical explanation in the technology section of their web site. It is actually better than what is on the tube manufacturer MB Microtechs site. As far as the safety if you have ever walked by a microwave oven when it's running you have been exposed to more radiation than wearing a GTLS watch will have in a month. Your body will dissipate the radiation in less than 24 hours with no effects if you choose the break open and sniff a tubes gas. So relax.