CO2 is a must for all homebrewers looking to keg. Of course, you can always bottle or use a gas mix (CO2 & N) but for most of us, that keg we use is just CO2. Recently, I picked up a cylinder of so-called “beer CO2”. I am here to tell you that CO2 - unless mixed with another gas such as nitrogen - is CO2. Most of the time, industrial-grade CO2 comes from the same production plant as food or beverage-grade CO2.

The slight difference between industrial-grade CO2 and food-grade CO2 is the type of tests that are done to qualify CO2 as beverage or beer gas-grade compared to industrial-grade. Currently, the FDA’s requirement for food-grade CO2 a 99.90% purity rating. The other .09% is made up of impurities such as hydrocarbons or nitrogen. Industrial grade CO2 is 99% pure CO2, also containing impurities such as hydrocarbons or nitrogen.

When talking impurities, we generally don’t talk in percents, so don't be mislead from the above paragraph. Went you look at impurities, they are referred to as PPM (parts per million) or PPB (parts per billion), so let’s look at hydrocarbons. Hydrocarbons might have 20 ppm in the CO2 that you are buying, which means that out of one cylinder, if you have industrial-grade CO2, it is 99% CO2. The remaining 1% has 20 ppm hydrocarbon. If you add up the remaining impurities it would equal 1%.

One impurity that all homebrewers should be aware of is benzene. Benzene is a no-no for homebrewers. If the CO2 that you are purchasing has high benzene levels, it will leave you and fellow drinkers with terrible headaches. When I say high levels, we are not talking about much. Benzene is usually an impurity that is referred to in PPB. The benzene level should be around 20 PPB.

Now, to the bad news - you as a homebrewer more than likely cannot test CO2 purity levels (unless you happen to have a gas chromatograph lying around). However, the supplier of your CO2 should have a report of what is contained in their CO2. Keep in mind, sometimes companies will tell you it is beer-worthy CO2. Ask what the difference is between their beer-grade and industrial-grade C02. Can they show you a report to compare the two? And if you are looking at purchasing a CO2/N mix or N for a stout, kindly disregard everything you just read.