All gas cylinders under pressure must undergo mandatory DOT testing every five years.
Carbon dioxide (CO2) tanks are used for various reasons, the most frequent being for CO2 fire extinguishers and home beer kegs. All gas cylinders and tanks are required by law to be professionally tested every five years according to Department of Transportation regulations. You should also perform maintenance checks more frequently to ensure safety between these mandatory tests.
1. Inspect the tank for rust and dents. Look for any swelling at the seams or surface cracks. Perform a visual inspection of the regulator, and ensure all connections are tight. If a crack is at the cylinder head, or crosses more than one thread, then the tank is unsatisfactory. Use a dentist’s angled mirror to inspect hard-to-see areas under the regulator.
2. Prepare a dilute solution of liquid soap in water. Add 2 drops of liquid soap to 50 milliliters of water. Fill a small dropper bottle or spray bottle if available. If not, use a cotton swab to apply the solution. Wet all joint surfaces of the regulator, neck and visible screw threads with the solution and check for bubbles. If you see bubbling, you have a leak at that joint. Tighten the joint and re-test until no bubbles appear.
3. Take the tank to a testing facility. If you are unsure of the tank’s condition, or if it does not pass visual inspection or the bubble test, have a professional check it.