Food-grade or technical CO₂: what the difference really is
The difference is not a percentage. It is a list of individually limited impurities, a certificate for every batch and a traceable chain from the filling plant to your tank.
Ask two suppliers for «food-grade CO₂» and you may get the same gas from the same source with different paperwork — or genuinely different products. The word on the invoice is not the specification, and the difference between grades is not the headline purity figure.
Why «99.9%» tells you nothing
Technical CO₂ is typically declared at 99.5% and food grade at 99.9%. That is a difference of 0.4 percentage points, which sounds trivial — and it is, on its own. The compounds that ruin a beverage act at parts per million: acetaldehyde changes the taste at 0.2 ppm, sulphur compounds are detectable by smell at even lower levels, benzene is a toxicity issue rather than a taste one.
So the food-grade specification does not simply raise the purity number. It lists individual contaminants and puts a ceiling on each of them separately.
| Parameter | Food grade | Technical grade | Why it matters |
|---|---|---|---|
| CO₂ purity | ≥ 99.9% v/v | ≥ 99.5% v/v | the headline figure, and the least informative one |
| Moisture | ≤ 20 ppm | not individually limited | corrosion, ice in fittings, carbonation instability |
| Oxygen | ≤ 30 ppm | not limited | oxidation and shortened shelf life |
| Total hydrocarbons | ≤ 50 ppm as methane | not limited | foreign taste and odour |
| Acetaldehyde | ≤ 0.2 ppm | not limited | detectable off-flavour |
| Aromatics (benzene) | ≤ 0.02 ppm | not limited | toxicity |
| Total sulphur | ≤ 0.1 ppm | not limited | rotten-egg odour at trace level |
| Ammonia, NO/NO₂ | ≤ 2.5 ppm each | not limited | taste and safety |
| Sensory check | required | none | catches what instruments miss |
Where each grade is allowed
| Application | Grade required | Note |
|---|---|---|
| Carbonating drinks, brewing | food | full ISBT list |
| Purging tanks and lines in a beverage plant | food | the purge gas contacts the product |
| Modified atmosphere packaging | food | direct contact with the food |
| Dry ice for cooling food or pharmaceuticals | food | the ice sublimates onto the product |
| Greenhouse CO₂ enrichment | food or dedicated horticultural | the crop absorbs it |
| Welding shielding | technical | no product contact |
| Fire extinguishers, pneumatics | technical | no product contact |
The dry ice line in that table is the one most often missed. A pellet is nothing but frozen CO₂ — whatever was in the liquid ends up in the ice and sublimates directly onto whatever is being cooled. Producers who supply the food and catering market state the grade explicitly for this reason; IceLab's food-grade ice, for instance, is positioned around exactly that: the raw material is certified CO₂, and that is what makes the ice safe to put next to food.
What a certificate does and does not cover
A certificate of analysis describes a batch at the moment it left the filling plant. It says nothing about the tanker that carried it to you, the hose used to transfer it, or the condition of your own vessel. Contamination in this chain is not exotic: a tanker that previously carried a different product, a hose left open in a yard, or a tank that has never been checked after an insulation repair.
- Ask for a certificate for every delivery, not a one-off specification sheet.
- Check that the parameters listed match the ISBT list, not just total purity.
- Record the certificate against the delivery in your traceability system — an auditor will ask for the link between a batch of product and a batch of gas.
- Run incoming inspection on moisture, oxygen and a sensory check at minimum. See the equipment for CO₂ quality control.
The full parameter list and how the ISBT and EIGA documents relate to each other is covered in a separate article.
The practical rule
If a site handles food or beverages at all, keep one grade on the whole site. Two grades in one yard means that sooner or later the wrong cylinder is connected to the wrong line, and the saving on technical gas for purging turns into a recalled batch. The price difference between grades is small compared with the cost of finding out the hard way.
Frequently asked questions
Is food-grade CO₂ physically different gas?
Often it is the same gas from the same source, purified further and, just as importantly, handled through a controlled chain: dedicated tankers and hoses, a certificate for each batch, and records that link a delivery to a production lot. The grade is as much about the process around the gas as about the gas itself.
Do we need our own laboratory if the supplier provides certificates?
You do not need a full analytical laboratory, but you do need incoming inspection. A certificate covers the gas at the filling plant; the checks at your receiving point cover everything that happened between there and your tank. Moisture, oxygen and a sensory check take minutes and catch the failures that actually occur in practice.
You may also need
Laboratory and analytical equipment for CO₂ quality control (DSTU, ISBT, EIGA)
CO₂ quality control laboratory kit (ISBT / EIGA / DSTU)
Model: LAB-CO2
A set of analysers and sampling equipment for controlling CO₂ purity, dew point, moisture and trace impurities to ISBT, EIGA and DSTU. Configured for the customer's product range and required parameters.
Price on request
On request
Cryogenic tanks for liquid CO₂ (carbon dioxide) 10–100 m³
Cryogenic tank for liquid CO₂ 30 m³
Model: CT-CO2-30
Stationary vacuum-insulated cryogenic tank for storing liquid CO₂ (carbon dioxide), geometric volume 30 m³. Supplied with valves, pressure control, vaporizers and a pressure-reducing unit; turnkey installation available.
Price on request
Made to order
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