Every so often, I see someone ask the question. Sometimes it can't be answered because a gun has been either sold/traded/stolen during the time frame it would have taken to determine just "how long" they do last? In other cases, it may be because the sights haven't been owned long enough to have reached their operational life span. In my case, I have three examples that are now (1)11 and (2)12 years old. For those that don't know what they are, they're a glass vial filled with Tritium gas (an isotope of Cesium, IIRC?) that glows 24/7 without exposure to light sources. In advertising and warranty info manufacturers typically warranty them for between 10 and 13 years. The 4 sets I have (3 old, 1 new) are now able to be compared for brightness. Life span being expressed is called "half life". It's the amount of time the isotope takes to decay to 50% of it's original value. The 3 old sets are all Meprolite S&W revolver adjustable sight sets. The "new" is a set of newly purchased Novak's with Trijicon vials on an M&P9c.
Exactly as listed at the end of 10-13 years in warranty info, the old sight set vials are one half the brightness of the new unit. This was checked in a totally dark room, after 15 minutes of vision acclimation with all 4 weapons lined up beside one another. They're still usable, just not as bright as one may like.
So now, I'm off to order new Meprolite sets for the S&W revolvers wearing them around here.

I don't know how long they last but I do know I can barely see my Trijicon sights during the day. Is this normal?

Approximately a decade some times less and some times more. Normal daylight indoors don’t see them outdoors see the little white circles. That’s my experience thus far with Warren Tactical sights. XS sights seem to be brighter.

Meprolight says 'up to 15 years'.

Meprolight, Military Tritium Self Illuminated Sights by Meprolight, Tritium

I read somewhere that tritium sights are half as bright as new after twelve years.

P.S.
Here it where I saw it:
http://en.wikipedia.org/wiki/Tritium
Half the remaining tritium in the sight will decay every twelve years.

The rep at an ACOG booth explained to me, regarding the different "lives" of the vials in their sights, that a technical process involved in the installation of the Tritium also had an affect. I was still drooling over the 4x model with the Docter red dot piggy backed. However, I think that it had to do with the pressure at which the Tritium was placed in its container or some such. Shrug.

Some places make fiber optic light gathering tube/tritium vial combo units for better day/night use.

You mean yours did not come with the optional plug in charger??

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Still Running Against the Wind

Yes Barb.
They appear as a standard set of "3 dot" sights till lowering lighting levels allow them to be seen over ambient light. Fortunately, the point of ambient lighting where we lose our regular sights, is where the Tritium becomes visible.
My understanding is that selection of colors other than the standard green, shortens life span of the gas in the vials. Till relatively recently, they were only available in green. They're now available in yellow, orange, blue, red but with the penalty of shorter life and lower brightness. My guess is, that some type of phosphor must be installed in the vial to change it's color and that addition or the shorting of the Tritium affects the life span?
And Gator has hit my hot button soap box subject! PLEASE Tru-Glo! Start making the combination fiber optic/Tritium sights for S&W products, not just Glocks! They're the best of both worlds!

The brand may play a part. The Meprolights on my Glock 17 are still glowing brightly after 8 years. The PT/Innovative Weaponry ones on my P220 stopped glowing after 3 years; they were replaced under warranty and the new ones lasted 5.

Just one side note...

DO NOT EAT THE TRITIUM!!!

Just ask Sip...

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Lost it all in a boat accident

If the sights stopped glowing after 3 or 5 years, its not them going out/the tritium decaying. It breaks down at a very predictable rate, 12 or 13 years you have half as much, so in theory, it will be half as bright as it was 12 or 13 years ago. That doesn't mean you can't see or use them. My experience was they were really bright when new (Trijicon). Even at half the brightness, they'd still probably light the room. And its a gradual decline, not all at once.

I don't like guns pointed at me. Its a quirk I have. But when you put a gun with them on the night stand, pointed away from you, its pretty darn bright. Point it away, and in a dark room the wall lights up. About the only way I'm happy is with something cloth tossed over the gun. If its thin, you can still see where the gun is, but it isn't lighting up the room.

So I guess the answer is how bright do you need them to be? Some people seem to want them replaced at 5 years, and it seems just the decay of the Tritum isn't the cause of them not being bright.

Oh, the Trituim is a hydrogen isotope, is it not?

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Dick Burg

Dick, I understand the halflife of tritium. I think the "useful life" may have just as much to do with the quality of the tubes containing the tritium. I chalked the first early failure of the PTs up to the possibility that the gunsmith who installed them used too much force and cracked the vials. The second set of vials were installed by the factory, so I think the materials themselves were at fault.

Your probably right Mr. B?
I don't have the periodic chart up on the wall in this room anymore. My Wife preferred another wall covering, alas? I can't recall whether Cesium is a byproduct of Hydrogen? I likely was thrown out of physics class that week!

Not long enough. 90+% dead on 1994 Glock. 80% dead on 1999 HK USP .45C. 50% dead on 2002 Springfield Champion .45. Not that I can see sights on a gun anymore in any light. Joe

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Wisdom chases me; I'm faster

Google is your friend! Its Hydrogen 3, a radioactive isotope of hydrogen. Used in bombs to increase yield (if you're not chemistry minded, it gets confusing fast.) For most of us, it makes glass tubes glow if they're coated with stuff, kind of like a florscent bulb without electricity. The most effective coating glows the green we're accustomed to seeing. Other things glow different colors, but aren't as good.

The point I was trying to make is that for some users, the 12.33 year half life means nothing. The good ones last beyond that if used in near total darkness. I had trijicon's on my one and only glock (a mistake never to be repeated by me.) The green glow was the best thing about that gun. Well, selling it was probably the best, now that I think about it.

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Dick Burg

I had a set installed on my duty gun in 1988, a 5903 (meprolights). I bought the gun in 2002 when the agency switched to Sig's. The gun is now serving night stand duty, residing in a drawer. The sights are approaching 22 yoa and though they have dimmed, are completely visible in low light. I also had a set on a P7M13 installed in 1984 (trijicon) that I finally replaced this year. I think 20 plus years of service is probably a bit more than one should expect on the average.

Randy

Your probably right Randy! But your noting 2 decades and still marginally visible is reassuring. I've recently started wear a watch (Uzi) with Tritium sapphires @ all face positions except sweep second hand. Nice to know I can count on at least 7-10 years out of a $75.00 watch.

Mr. B,
Yup, knew the primary use of it. The Israeli's were the first to use it for this specific application I believe? No doubt discovered during their non-existent weapons program while working on the thermonuclear device's that they also don't have?

Tritium (3H or hydrogen 3) has a half-life of just over twelve years. The half-life is the amount of time it takes to decay half of a given sample's energy output. It decays into 3He or helium 3 by releasing an electron and an electron antineutrino. The electron and the electron antineutrino release over 18keV of energy, as beta radiation. Beta radiation cannot penetrate human skin and the only way to get it into the body is through ingestion.

Back to our sights...the sight capsules have a phosphor coating on the inside that glows when excited by beta radiation emitted by the tritium. Different color sights have different phosphor mixes.

Premature failure is most likely caused by the failure of the container or the phosphor coating. My guess is with the capsule failure. Hydrogen is a tiny little molecule and will get out of the most minute crack.

Russ, who actually studied physics and chemistry all those years ago.

I have a 640 with a Trijicon front sight dated '99. It is dimmer than a set from '04 but still can be seen.

The good news is that if you send the sight to Trijicon they will place a new vial in the sights for $18.

I had PT put them on my P7 in 2003....this year they were still fairly bright but my front sight loosened and I decided to put on my spare pair, without night sights...I enjoyed seeing them glow on the night stand but now that I don't keep a gun on the nightstand anymore, I didn't really feel the need to replace them...

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Thirty characters. Exactly...

The half-life of tritium is 12.33 years. Yes, I'm a radiation physicist. That being said, the job plus a $1.50 will get you a cup of coffee.
Anyway, that means the amount (intensity) of light that you see will be cut in half every 12.33 years. That also means that after two half-lives (24.66 yrs), the light intensity would be reduced to 1/4 of its intensity "right now."
Now, the practical aspects of all this stuff. I don't like bright sights. If you have "fresh" tritium sights, just think if that perp in the night comes around behind you. Heck, he can see you from 15 feet away; or at least he can see the gun's sights, both front and rear.
I have purposely installed a front sight on some of my guns that other folks "threw away" when they got new ones. Of course, the gunsmith keeps them in his drawer and will give them to you free. The used front sight is plenty bright enough to see in a darkened situation without being any brighter than necessary.
And, you saw that I said front sight only. That's the only sight you need to see, especially at rather close range. At 25 yds, the front sight alone wouldn't be enough, but you can't see the perp that far away anyway.

And to RBurg who doesn't like Glocks...I'm sorry you got a bad one. Never heard of a bad Glock. I have/had eight of them, my son-in-law SWAT cop has several and I've shot them for twenty years without a misfire. I would never be able to say that about some Smith semi's I have known.
Sonny

I had a set installed on a Commander about fifteen years ago. They stayed visible for about three years, then got so dim they weren't noticeable. Too expensive for what I got out of them.

I paint my sights with Radium. It's a really good sourse of illumination in darkness and has a half life of 1602 years.

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Memory of Randy Freas-Rimfired

Yeah Mickey,
Just don't moisten the artists brush by licking it, and you'll be just fine!
(Elgin Watch Co. employee instruction manual)