Overview
Manufacture/test date
You can determine the date of manufacture of a compressed gas cylinder by the codes stamped into the cylinder. In the picture provided, the date is given at item 3 and is shown as 4-55. This indicates the manufacture date as April of 1955. In general, cylinders must be hydrostatically (i.e., pressure) tested every 5 years. In the picture this is shown at item 5 as 4L60, 4L65, etc. indicating April 1960 and April 1965. Ten year and other tests are also allowed.
What is important with regard to cylinder dates is that if you find an old cylinder, especially those that have not been tested in ten years, note that in the database and report it to a Specialist. Cylinders that are outside of the hydrostatic test date may still be used but they may not be refilled until tested. No further action is needed by the auditor.