TRITIUM SAFETY
Is tritium safe to carry every day? Yes. Here is the physics.
A tritium vial glows for up to 25 years with no battery, no charging and no external radiation. This page explains how it works and why it is safe to hold, wear and keep in your pocket.
How a tritium vial makes light
The technology is called GTLS: gaseous tritium light source. Three things happen inside the tube, in this order, millions of times per second.
Tritium decays
Tritium is a heavy form of hydrogen. Each atom eventually releases one low-energy electron (a beta particle) and becomes ordinary helium. No heat, no chain reaction.
It hits the phosphor
The inside of the glass is coated with phosphor, the same family of materials used in old CRT screens. The electron transfers its energy into the coating and is absorbed there.
The phosphor glows
Excited phosphor releases that energy as visible light. Different phosphors give different colours. The glow is continuous: day or night, on or off your keys, for years.
What kind of radiation is it, and can it get through skin?
Two direct answers first, then the explanation.
What does tritium give off?
Beta radiation only.
A beta particle is simply an electron. Tritium's is the weakest beta in common use. It emits no gamma rays, no X-rays, no alpha particles and no neutrons. There is nothing in a tritium vial that can travel through a wall, a body or a room.
Can it pass through skin?
No.
The electron travels about 0.006 mm in tissue. The outer layer of your skin is dead cells about 0.07 mm thick, more than ten times that distance. Even if you pressed a bare, unglassed vial against your arm, the radiation would stop in dead skin before reaching a living cell.
Drawn to relative scale: the electron's whole journey into skin is less than one tenth of the dead layer. This is why beta from tritium is classed as an internal hazard only, meaning it matters only if the gas is swallowed or inhaled, and a sealed vial gives no external dose at all.
Why nothing escapes the glass
Inside the vial the glass adds a second wall on top of your skin. Here is how far the electron gets against everyday materials.
The numbers behind the claim
Four figures explain almost everything about tritium safety.
Among the lowest of any radioactive isotope. Average energy is only 5.7 keV.
Less than one tenth of the dead skin layer. It cannot reach living cells from outside.
Brightness halves every 12.3 years (the half-life). The vial stays usable in the dark for up to 25 years.
If tritium ever enters the body, half of it is gone in about 10 days through normal water turnover.
Put it next to things you already do
Radiation is measured in millisieverts (mSv). A sealed tritium vial contributes nothing measurable to your yearly total.
The chest CT bar is capped at the chart width. Values are typical public-health estimates and vary by location and equipment.
What if a vial breaks?
The vial sits inside the titanium body and very rarely breaks. If it does, nothing dangerous happens: tritium is a gas, so it spreads out and is gone.
Why the risk is low
A 3 x 22.5 mm vial holds about 0.04 mg of tritium gas. Tritium gas is barely absorbed by the body and is mostly exhaled, so even the extreme case of inhaling that entire amount at once works out to roughly a few days of natural background radiation. In reality the gas spreads through the room in seconds and you breathe in only a tiny fraction of it, well below a single day of background. There is nothing to clean up beyond a bit of glass.
Three things not to do
Do not crush, cut, drill or heat a vial on purpose.
Do not open a vial to reuse the phosphor. The gas is the useful part, and it is gone once the seal breaks.
Do not give loose vials to children. The glass is the hazard, not the tritium.
The same light you already trust
Tritium light sources have been used for decades wherever a glow must work with no power and no maintenance.
Swiss made, sealed for life
The vial is the part that matters. Ours come from Switzerland and are never touched once sealed.
Swiss GTLS vials
Made by the same manufacturer that supplies watch and instrument brands worldwide.
Common questions
The ones we get asked most.
What type of radiation does tritium give off, exactly?
Beta radiation only, and the weakest kind: a low-energy electron with a maximum of 18.6 keV. No gamma, no X-ray, no alpha, no neutrons. It is stopped by a sheet of paper, the vial glass, or the dead outer layer of skin. This is why regulators treat sealed tritium light sources as safe for the public.
Can I take it through airport security?
Yes. Sealed tritium products are permitted in carry-on and checked luggage worldwide. They do not set off metal detectors or radiation portals; the glass blocks the only particle tritium emits. Tritium watches have flown for decades without issue.
Is it safe to sleep with it next to me, or keep it in a pocket all day?
Yes. There is no external dose from a sealed vial. Distance, duration and body contact make no difference because nothing leaves the glass except light.
Will it stop glowing?
Slowly, and never suddenly. Brightness falls to about half after 12 years and a quarter after 24, which is why we rate the glow life at up to 25 years. It fades gradually rather than switching off.
Does it need charging or sunlight?
No. Unlike photoluminescent paint, tritium does not store light. It makes its own, continuously, whether it has been in a drawer for a month or in the sun all day.
Is tritium the same thing used in nuclear weapons?
The isotope is the same, but the quantity is not comparable. A standard 3 x 22.5 mm keychain vial holds about 0.04 mg of tritium gas, roughly one hundred-thousandth of the amount used in a weapon, with no possibility of any chain reaction. It is a light source, nothing more.
Can I get a vial in any colour?
Colour comes from the phosphor coating, not the tritium. Green is the brightest because our eyes are most sensitive to it. Other colours (ice blue, orange, white, red, purple) use different phosphors and are dimmer by design.
Light that never asks for anything
No battery. No charging. No radiation you can measure. Just a glow you can find in the dark.
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