A good customer (all our customers are good, of course) recently asked us to figure out exactly how many bump tests they would get from a 58L of NIST Traceable Gas for their new Gas Clip Technologies Multi Gas Clip (MGC) Monitors (with 2 month battery charge life). The quick answer - a little over 300, and maybe as many as 600. But there's a catch.
Calibration gas has a shelf like. It's longer than a gallon of milk, but still shorter than you might expect. The 4-gas mixture for the MGC has a six month shelf life. After that time the gas will begin to degrade and the specific percentages will no longer be so specific. If you haven't used it by the date on the cylinder, you'll need to discard it and replace it.
We came by our 300 bump test number by taking the flow rate of a regulator at 0.5 LPM. Worst case scenario it will take you take 20 seconds per monitor (really the time will be closer to 10 seconds - thus our possible 600 number). Using the 20 second estimate that equals 0.1666 liters (1/3 of 0.5 liters) of cal gas per bump test. 58 liter cylinder divided by 0.1666 equals a little over 300 tests.
Storing the cylinder properly is also important. Like a pantry for confined space safety, your gas should be kept in a cool dry place. Not always possible, but please avoid extreme high (100 degree F +) temperatures. The 4-gas (quad) mix has a relatively short shelf life to begin with. The trunk of a car would not be considered a good place to keep cal gas. In particular the H2S will deteriorate faster.
When transporting the cylinder, it should be protected from dropping or hard impacts. The aluminum cylinder is tough, but any compressed gas should be treated with respect. You are not able to take this on an airplane. When shipping, we use a heavier thancali normal box, and it is considered haz mat by UPS, etc., with special labeling and training for the shipper.
Calibration interval recommended by the manufacturer for the Gas Clip MGC is once every 6 months (180 days) minimum. For bump tests, best practice is before each use. This is particularly true for confined space entry. The gas detector is then verified to be working, with alarms functioning, before entering a potentially deadly environment. We have customers all over the block on this, mostly related to what their application is. But confined space entry is not something to skimp on.