We don’t eat expired food, so why would we use expired calibration gas?
Calibration gas is a very vital part of making sure that your gas monitor is going to perform as it should. Whenever you perform a bump test or a calibration on your gas monitor, calibration gas is something that you must have on hand. Calibration gases have set amounts of gas in the bottle that is exposed to the sensors of a gas monitor. If you use expired calibration gas there is a very good chance that your calibration is not a proper diagnosis of your monitor.
Every bottle of calibration gas should have an expiration date on it, and that expiration date is based on the shelf life of the gas in the bottle. Over time, the amount of gas in the bottle may diminish or disappear entirely. Time, environment changes, and reactions to other chemicals can all deteriorate the amounts and quality of gas in your cylinder. Gas concentration is also a factor that can change the shelf life of a gas bottle. If there are a higher concentration of reactive gases, in some cases they can be certified for a longer timeframe than a low concentration.
Even with the gas being in a sealed container and in a climate-controlled environment, there is still an expiration date that will be met sooner or later. There are essentially two different types of gas that is used in these calibrations. They can be broken down into reactive gases or non-reactive gases. The most common non-reactive gases in calibration bottles are methane (CH4), pentane (C5H12), propane (C4H10), hexane (C6H14), carbon dioxide (CO2), hydrogen and nitrogen. These non-reactive gases typically have a shelf life of around 36 months. With that being said, the most common reactive calibration gases are hydrogen sulfide (H2S), chlorine (CL2), nitric oxide (NO), nitrogen dioxide (NO2) and ammonia (NH3). Because these gases are more likely to react inside the bottle, the time frame on these are around 6-12 months.
A quality gas bottle manufacturing company will produce a cylinder with the smoothest internal walls possible. Even though it is at a microscopic level, the smoother the inside of the bottle equals a smaller surface area which helps with reactions in the bottle. Another factor in bottles with rough internal walls is the ability for the rough parts to hide contamination that would have been present on a smooth walled bottle. Over the years, bottle manufacturers have been able to produce smoother and smoother bottles which has led to a longer shelf life of the gases.
Below is a table of common gases and their usual shelf life before expiration:
|GROUP||GAS||APPROXIMATE SHELF LIFE|
|Group 1||LEL (Methane, H2, Pentane, etc.)||28 months|
|Group 2||H2S||19 months|
|Group 3||Cl2||7 months|
|Group 4||4-gas bump testing cylinder||9 months|
|CO bump testing cylinder||9 months|
JM Test Systems carries a complete line of calibration gas, regulators, calibration cups, tubing and gas detectors. Please contact us for anything you may need to make sure you and your employees are safe and their gas is always current and within use by date. JM Test also rents gas detectors, bump test stations and we can send gas to you with your order!