MSA 10048280 Calibration Gas Cylinder — 34 L

MSA's 34-liter calibration cylinder for its ALTAIR family — the factory-specified gas for the monitors many industrial fleets standardize on.

Read the full MSA 10048280 Calibration Gas Cylinder review →

Cal-gas expires like the sensors it tests: date the cylinder on arrival and track it with the instrument log.

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What calibration gas is for

A gas detector drifts. The sensor output for a known concentration changes with age, temperature, humidity and exposure history, so an instrument that read correctly last quarter may not read correctly today. Calibration gas is the reference: a cylinder holding a certified concentration against which the instrument's response is checked and, where necessary, adjusted.

Two operations use it and they are not the same. A BUMP TEST applies gas briefly to confirm the sensor responds and the alarm sounds - it proves the instrument is alive, not that it is accurate. A CALIBRATION applies gas long enough for a stable reading and adjusts the instrument's span to match. A bump test is a daily-use check; calibration is the periodic correction.

What the guidance actually requires

OSHA does not set a single universal calibration interval for portable gas detectors. The widely followed position, set out in the ISEA statement on instrument verification and echoed by manufacturers, is a bump test before each day's use and a full calibration at the interval the manufacturer specifies - commonly monthly to six-monthly, and immediately after any instrument reads unexpectedly, is dropped, or is exposed to a high concentration.

Where a confined space entry programme applies under 29 CFR 1910.146, the atmospheric testing it requires is only meaningful if the instrument doing the testing is in calibration. The records that prove it - date, gas lot, technician, result - are part of the programme rather than an optional extra.

Cylinder handling and shelf life

Calibration gas has an expiry date and it is not a formality. Reactive gases degrade in the cylinder as they react with the walls and the valve; hydrogen sulphide and chlorine mixtures have notably shorter certified lives than methane or pentane. Calibrating against expired gas produces an instrument that is confidently wrong.

Store cylinders upright, below the temperature the label specifies, away from direct sun, and check the certified concentration on the label against what the instrument expects before starting. A cylinder is spent well before it is empty: once the pressure falls below the regulator's working range the delivered concentration is no longer the certified one.

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Written by Steven Eaton, WC Safety editor. WC Safety is an independent PPE review site, holds no inventory and sells nothing directly; Amazon links are affiliate links that earn a commission at no cost to you and never affect the assessment. This page is not medical, legal or regulatory advice.

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