Calibration gas is an important component in ensuring the proper performance of your gas monitors. Regular calibrations promote the accurate measurement of gas concentration values. During calibration, a unit’s installed sensors are to be exposed to their set concentrations of calibration gases. Based on the sensors’ responses, the unit will self-adjust to compensate for declining sensor sensitivity, which naturally occurs as the installed sensors are used or “consumed.” Using incorrect or expired calibration gas can cause an improper calibration, resulting in unsafe operation and an improper diagnosis of instrument malfunction.

Calibration gas expiration dates are listed on every Industrial Scientific calibration gas bottle. The expiration date is based on the calibration gas shelf life of each bottle. The concentration of gases in a cylinder may decrease or eventually disappear over time due to the gas reacting to moisture, oxygen, or other chemicals. Once a cylinder is expired, it should no longer be used.

This statement commonly raises several questions, mainly “How does calibration gas expire?” or “Why can’t I calibrate with expired gas?” The answer is quite simple.

Let’s say you are about to perform your monthly calibration on one of your instruments. You gather your instrument, regulator, tubing, calibration cup, and your gas bottle. While connecting the regulator to the gas, you take a moment to read the gas bottle’s label and notice that the cylinder expired last month. Are you still going to calibrate the instrument with that bottle? It’s only a month past expiration, how bad could it possibly be?

Now let’s say you’re cleaning out your kitchen. You find an unopened carton of milk that’s been sitting in the back corner of your refrigerator. You check the label on the carton and see that it expired last month. Are you still going to drink it? It’s only a month past expiration, how bad could it possibly be?

While this is probably common sense, it is a simple truth that milk can decrease in quality over time, even while stored in a sealed container in a controlled environment. A cylinder of calibration gas is no different. As stated earlier, reactive gases can degrade over time, and some do so faster than others. Over a period of time, chemical reactions take place inside the cylinder (much like the carton of milk) and can alter the contents of the bottle. There is nothing a manufacturer or user can do to extend calibration gas shelf life, as we simply cannot control the nature of these reactive gases.

For these reasons, it is best to always use a gas cylinder that has not reached its expiration date. For safety purposes, never calibrate a gas detector with an expired gas cylinder. If you wouldn’t drink expired milk, why would you calibrate a life-saving instrument with expired gas?

The following chart shows the expected calibration gas shelf life of Industrial Scientific cal gas:

Calibration Gas Shelf Life

Note: Group I as well as H2S, NO2, and SO2 from Group II can be used in a combination cylinder. If using a combination cylinder, the expiration date defaults to the gas that will expire first.













For more information on the importance of calibrating your instruments, click here.


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This article was composed by Michelle Hammons, Product Manager, and Bryan Szczur, Marketing Project Coordinator.