CO2 Stamps: what they are and what they mean!


CO2 Stamp Explanation

CO2 cylinders are necessary for drafting beer (or whatever beverage you’re running through your kegerator/keezer) because they provide that wonderful beer gas to push the lovely beverages into our glass. Maintaining them isn’t difficult yet understanding them can seem overwhelming – at first. We’re here to help you navigate and understand what all those weird looking signs, symbols, and characters that are stamped onto your cylinder actually mean. So, whether you end up buying a brand new CO2 cylinder or maybe you find a great deal at a garage sale, you can be sure that you know whether or not your cylinder can be serviced or filled without having to spend additional money getting it up to date.


  1. DOT-3AL1800: “DOT-3AL” is the US Department of Transportation’s specification for seamless aluminum cylinders with a minimum service pressure greater of 150 psi. “1800” is the service pressure rating of the cylinder in psi.
  2. CC357769: This is the serial number for the cylinder
  3. M5659: This is the “M number” or manufacturer’s number issued to Metal Impact South by the US DOT.
  4. 11A16: The “11” represents the month of manufacture, November, and the “16” represents the year of manufacture, 2016. The “A” in the middle is the mark of the independent inspector. The manufacturing and testing of DOT-3AL cylinders must be witnessed by an approved independent inspector. The “A” is actually an arrowhead symbol identifying Arrowhead Industrial Services as the independent inspector.
    All CO2 cylinders have a manufacture date. Re-certified CO2 cylinders also have a certification date. The most recent date on the cylinder is the currently active date.
    The most important date to know when purchasing a cylinder is when the cylinder was last re-certified. Re-certification includes hydro-testing. The Department of Transportation (DOT) requires that most portable CO2 tanks, both new and used, be re-certified every five years. Nitrogen and other high pressure inert gas cylinders generally have a 10 year re-certification requirement (although there are exceptions). Certification must be performed by a DOT-licensed facility.
  5. M with line coming down through it vertically: This is a symbol for Metal Impact. The vertical line is a capital i.
  6. 5#: This is the maximum mass in pounds of CO2 that can be filled into this cylinder.
  7. T7.40LB: Tare weight of cylinder and valve in pounds.
  8. TC-3ALM124: “TC-3ALM” is Transport Canada’s specification for seamless aluminum alloy cylinders with a minimum service pressure greater of 1.0 Mpa. “124” is the service pressure rating of the cylinder in bar.
  9. T3.36KG: Tare weight of cylinder and valve in kilograms.