Is there such a thing as "food grade CO2"?

According to The Brewing Network, industrial and food grade CO2 generally come from the same plants:

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.

However, the nature of those impurities extremely important. They go on to suggest:

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.

They suggest you ask for a profile of the impurities, although I suspect that Dick's will be unable to comply. You will have to assess your own tolerance for risk, but you may better off seeking a more appropriate local vendor.

Not sure how it applies to C02 specifically, But Food-Grade, anything (in the US) means special requirements on transport and handling, which implies more expense. So even though the same plant may produce it, the pipes leaving the plant have to be food grade, the tanks the product goes into has to be food grade. The non-food grade version will go through less expensive /less-maintained/less-cleaned pipes and into similarly treated containers.

So your CO2 in a painball gun, could have oil in it (or remnants of oil) from any of the things it's passed through Tanks, Tubing, fittings, valves.... which won't hurt the gun, but would not be good for food uses. The other than oil, is lead, as most fittings (Brass) can and do contain lead, Most food grade CO2 fittings are stainless or aluminum to avoid lead contamination.

Food grade CO2 is so cheap for the little you need for carbonated water I wouldn't bother with paintball gun gass you get at Dicks. Its $21USD for a 25lb tank of food grade CO2 here in small town Michigan, with no deposit on the tank. I would expect it to be even cheaper in a larger city.

Ask around anywhere that sells kegs of beer. Food grade CO2 can be used to dispense beer, keeping it from going bad as fast as it does with hand pumps (Atmospheric Air). So some of your keg-beer shops will have it. All Pop Distributors will have it too since its required for both BiB and premix systems, but they tend to cost more for the same CO2.

Serious Eats just took on this issue. After some explanation of what "food grade" means as it relates to CO2, they go on to say,

I got in touch with Dave Arnold, a carbonated-cocktail pioneer, and he told me that although he gets his carbon dioxide from a 'welding supply' place, that same source also supplies carbon dioxide to the food industry and medical industry. As long as you tell the supplier you intend to use the gas for food applications, they should be able to give you the right type.

So start by asking the folks at your local homebrew shop or restaurants that use CO2.

In summary: before you go in on a tank of gas, check out whether there are good places to get it filled near you. If they don't know what you're talking about, stay away and find a different supplier who understands that you need everything you use to be food-safe. But ultimately, this is a DIY job and you (the DIY-er) need to be ok with assuming the responsibility of ensuring all your components and ingredients are safe for whoever you plan to serve your drinks to.

Food grade CO2 is not meant for human consumption. For that, you should use Beverage Grade, which is more pure than Medical Grade. Both major soft drink companies have Beverage Grade as their minimum guideline. Food Grade CO2 is a dirty gas that isn't tested for several carcinogens...because it isn't meant to be ingested. You need to go to CO2 providers that only handle Beverage Grade, because once you put Beverage Grade CO2 in a container that has Food Grade (or worse), then you no longer have Beverage Grade CO2.

Meats are indeed packaged with CO2, as well as various mixtures of gases. Some inhibit bacterial growth while others slow oxidation and loss of bright red color. Nitrogen is commonly used with CO2 to accomplish this in "counter ready" packages of beef. Pork sausage is protected with a mix of 20%CO2/80%N2. Gas companies sell lines of products specifically for meat, and the segment is often referred to as Modified Atmosphere Packaging, or similar title. CO does have application in this arena, but the predominant gases to shield meat products are CO2 and N2.

Also, CO2 comes from the same bulk tank and through the same lines into the gas packaging plant. The cylinders are commonly interchanged for service, whether industrial or beverage. They are usually kept in continuous grade service by convention as this eases plant production, but it is not required.

The quality control occurs in two ways. The first is by the ultimate source gas selection. For example, if one wants CO2 for beverage use, the gas will come from an ethanol plant. The CO2 plant is on site where ethanol is made and pipes over the raw product that is essentially a by-product of ethanol production. The CO2 is refined to a desired grade and involves removal or moisture, and the expected known contaminants from the ethanol plant. It is then liquified for easier storage and transportation. As the CO2 is being generated, the production stream is continuously sampled to make spec. The CO2 plants produce product to meet the demand for the largest customers, thus any plant making CO2 for beverage application and having distribution to Coke, for example, makes product to meet that spec. So, it certainly meets what you need it for too. The truck that carries the product will likely be kept in captive service but that is not required. A similar situation exists for medical O2, USP grade. The plant makes it, ships it in any old O2 truck (they are all super clean anyway) and puts it in the same bulk tank as that from which we fill welding and cutting grade, Industrial, oxygen. (It has always interested me that medical Grade Oxygen, USP, has a lower minimum purity requirement that Industrial. There are strict controls over the USP filling process that will safeguard patients using the gas, but the spec is typically the lowest purity by percentage.) Plant piping is chosen for pressure and purity and can be brass of a certain type, stainless tubing or even monel. (Acetylene plants use black iron pipe.)

CO2 is sourced at other plants, some of which may contain ammonia as a trace contaminant, as well as other bad actors. As can be expected, beverage product does not come from there.

So, the first control is exercised when we choose the source of the gas. The next control comes from conventional gas quality instrumentation such as the use of gas chromatography, IR spectroscopy, flame ionization hydrocarbon analysis and trace O2 analysis. The CO2 grades can be: industrial, bone-dry (really!), Super Critical Fluid, USP, Research, 2.8, 3.0, 4.0, (numbers relate to how many "nines" purity by percentage,) Instrument, Laser, etc. Oh, and beverage grade too. It is worth noting that the gas supplier is free to market as they wish except for medical grades, USP and NF, which are prescribed by the FDA. So, one company's offering may name a grade with similar nomenclature, but the specs will be different.

Quality is controlled by choosing the sources and then doing the analysis. If you want to know what you are getting, ask for a spec sheet for the gas which gives guaranteed minimum purity for any CO2 marketed under whatever grade you happen to be getting from the gas company. This just catalog spec. If it is from a gas company such as Praxair, Air Liquide, or Linde, this info is easily found on their websites. If you are getting product from a distributor, the good ones will easily provide this as well. If they can't get a better source who will. NuCO2 is a national beverage gas supplier bought by Praxair a while ago and is dedicated to bev carb. In general, it is best to tell your gas supplier the intended use, ask what grade you should use, and why. Take a look at Praxair wersite and beverage carbonation for a good example.

Hope this helps.

medical grade co2 has 99.99% purity rating. Both beverage and food grade co2 both have a 99.95% purity rating. Industrial co2 has a 99.90% purity rating. Food grade co2 is in fact beverage grade co2. I went to AIR GAS to get beverage grade co2 and they gave me food grade because they are equivalent. If you search "beverage grade co2" on Air gas's website it pulls up food grade co2. Its all about the purity of the gas. All co2 is made the same (according to the employee at airgas). Its all about how the co2 is stored and handled, and the FDA has put compliance laws on food aka beverage grade co2, making distributers store the gas in specific tanks just for food or beverage grade. The comments above stating that food grade co2 is "dirty gas" is invalid. Its pure enough for human consumption based on FDA compliance. Medical grade co2 is not reasonable to get for consumption purposes.