What Is the Shelf Life of Calibration Gases?

If you work closely with gases, you need to know that your gas monitoring systems are reliable. Otherwise, there’s no way to know if the area — and you — are safe. While calibration gases help by compensating for the inevitable decline in sensitivity that they all experience, these gases do eventually expire. An expiration date is typically listed on the gas cylinder and its Certificate of Analysis (CoA). The actual shelf life may differ slightly from this expiration date, but abiding by the earliest date listed must always take priority to maintain a safer environment.

Learn more about the shelf life of calibration gases and how to handle them when they expire.

Do Calibration Gases Expire?

Yes, and quickly. You can find the specific expiration date on the gas container and by calculating the gas’s shelf life, which refers to a given gas’s chemical stability. Over time, the gas is exposed to moisture, contaminants and other chemicals, which alter the concentration of gas in the cylinder. Eventually, the concentration degrades to the point where the gas can no longer calibrate sensors accurately. 

The expiration date is meant to prevent the mixture from reaching that point. If it does, your facility may be in violation of Occupational Safety and Health Administration (OSHA) standards or those set by the Environmental Protection Agency (EPA). It also puts employees at risk.

Gas cylinder shelf life varies based on the stability of the gas in question and storage conditions. Nonreactive mixtures can generally last up to 36 months, while reactive gases usually have a shelf life between 8 to 12 months. That said, always defer to the expiration date printed on the canister and contact your supplier if you’re not sure.

What Determines Gas Shelf Life?

Shelf life can vary for reasons that aren’t always easy to identify. Fortunately, there are a number of factors that we do know impact longevity. They include:

• Gas type: The gas’s reactivity has a profound impact on its shelf life. Inert gases typically last far longer than reactive ones. This is partially because reactive molecules are more likely to stick to the cylinder’s interior, diluting the concentration. That said, there is a wide range of shelf lives within each category.
• Cylinder design: The materials and technology used in the cylinder can also impact shelf life. Aluminum cylinders aren’t vulnerable to the same corrosion as steel cylinders. Many even have their internal surfaces treated to minimize the possibility of absorbing gas molecules. Well-designed valves and seals can also prevent leaks and issues with external moisture, extending shelf life further.
• Moisture and contaminants: If water vapor gets into the cylinder, it can react with calibration gases and dilute the concentration or even form corrosive acids. Impurities can have the same effect. This is why many calibration gas suppliers heat and purge the cylinder with inert gas before refilling it. The process removes atmospheric contaminants and moisture to make sure the gas lasts as long as it should.
• Storage practices: Cylinders need to be stored upright and kept 20 feet or more away from combustible materials. They should also be kept out of direct sunlight, as the heat can accelerate chemical reactions and shorten the shelf life of calibration gases. Climate-controlled calibration gas storage areas are almost always the best place for them. Consider organizing storage areas by expiration date to keep the oldest product easiest to access when it’s time to swap tanks.

With so many variables affecting shelf life, getting it right can be challenging. Meritus Gas Partners is here to help. Our network of distributors has the expertise to help you choose the right calibration gases for your specific storage needs — find a partner near you to get started.

How to Manage Calibration Gas Expiration

The first step of safe calibration gas handling is to find the expiration date printed on the cylinder itself. The process is pretty simple. Just locate the label on the shoulder of the calibration gas cylinder and look for the expiration date listed there. Some cylinders may say “Use By” or similar language. You will also find other helpful information on the label, such as the certified concentration and a lot number for traceability.

The cylinder should also come with a CoA, which provides you with more detailed information about the calibration gas. For example, it will list the certified analytical uncertainty for the gas. This number, typically written as a percentage, gives you a margin of error for the gas’s concentration. Any cylinder that does not have a legible, unaltered label or CoA should not be used. Doing so can easily compromise gas sensors and put people at risk.

Once you’ve identified the expiration date, you can add the cylinder to your inventory rotation. This rotation should follow a First-In, First-Out (FIFO) methodology. Track each cylinder via colored tags or a digital spreadsheet, and swap them out when their time comes. No cylinder should be used past its expiration date, so the tags or spreadsheet should be as detailed and user-friendly as possible. Make sure all staff are trained on locating and abiding by expiration dates.

End-of-Life, Safety, and Disposal

Once the cylinder has reached the end of its life, it’s time to safely dispose of it and install a new one. You may also need to install a new cylinder if the existing one gets damaged, is exposed to extreme temperatures or fails a routine calibration check.

Unfortunately, the old cylinder can’t simply be thrown in the trash. Any residual gas represents a potential hazard. Instead, contact your gas supplier and ask about safe disposal methods. Many suppliers have a return or recycling program that can take care of cylinders you no longer need. These programs and the supplier’s disposal procedures must comply with standards set by the EPA, Compressed Gas Association and other agencies.

Find the Gases You Need With Our Partners

The shelf life of calibration gas is a complicated business. That’s where we come in. Meritus Gas Partners unites a range of independent gas suppliers to meet the needs of professionals across industries. From calibration gases for sensors to shielding gases for welding, our partners are equipped to supply the gases you need and dispose of them, too. Each distributor offers the personal touch you deserve and the high-powered corporate infrastructure you need to get the job done well and on time.

Get started today by filling out our contact form or finding a partner near you.