How long does calibration gas last? It depends almost entirely on the reactivity of the gas inside the cylinder. Using expired calibration gas is one of the most common causes of a false bump-test pass — so it pays to know the shelf life of each gas type and plan reorders accordingly.
What affects calibration gas shelf life
Three things drive shelf life: how chemically reactive the target gas is, the cylinder material, and the concentration. Reactive gases slowly interact with the cylinder wall and lose concentration; stable gases last for years.
Shelf life by gas type
| Gas type | Typical shelf life | Examples |
|---|---|---|
| Reactive & high-reactive | 6–12 months | H2S, SO2, Cl2, HCl, NH3, NO2 |
| 4-gas & non-reactive mixes | 12–36 months | CO/H2S/CH4/O2 quad, CO, methane/LEL |
| Pure & UHP gases | Up to 48 months | N2, CO2, zero air, methane CP |
The exact shelf life is printed on every cylinder and Certificate of Analysis. For the full reference, see our shelf life reference page.
Why reactive gases expire faster
Gases like hydrogen sulfide and chlorine are chemically active and gradually adsorb onto the cylinder's interior, dropping below tolerance. That is also why reactive gases are filled in treated aluminum cylinders rather than steel.
Storage best practices
- Store cylinders upright, indoors, between roughly 0–50 °C, out of direct sun.
- Use oldest stock first and check the expiration date before every calibration.
- Don't use gas past its expiration — accuracy is no longer guaranteed.
- Order reactive gases closer to when you need them; buy non-reactive mixes in larger quantities.
Shop fresh-filled calibration gas →
Trigas USA fills on demand and ships in 48 hours — you get maximum usable shelf life, not cylinders that sat in a warehouse. NIST-traceable, 15–30% below OEM.
Frequently asked questions
How long does calibration gas last?
Reactive gases (H2S, Cl2, SO2) typically last 6–12 months; 4-gas and non-reactive mixes 12–36 months; pure and UHP gases up to 48 months.
Can I use calibration gas after its expiration date?
No. Past expiration the concentration may be out of tolerance, which can cause a false bump-test pass.
Why do reactive gases expire faster?
Reactive gases slowly interact with the cylinder interior and lose concentration, so they have shorter certified shelf lives.