O2 Impurity in Carbon Dioxide: How Much is Too Much?

I recently saw a post on a brewing forum where someone was wondering about air contaminated carbon dioxide and its impact on dissolved oxygen levels in carbonated beer. Air in CO2 really can raise the dO2 levels in your beer, so I thought it would be worth discussion.

Back sometime in the late 1980s (I think) someone passed along to me a table showing the exact amount of dO2 that would be picked up in beer if specific amounts of CO2 were injected into a process pipe or finished beer vessel. I’ve been hoping to find a copy of that article ever since, so maybe someone out there can help steer me to it. But in the meantime, with a tip of the hat to the original author(s), here is a copy of the table:

Co2 Injected O2 Impurity


O2 Impurity


O2 Impurity


0.5 V/V 7 ppb 35 ppb 142 ppb
1.0 V/V 14 ppb 71 ppb 284 ppb
2.0 V/V 28 ppb 142 ppb 567 ppb
Dissolved oxygen added to the beer during injection

So knowing all of this, what’s the best way to determine whether a CO2 supply is contaminated with air? There are two approaches. First is to simply measure your CO2 source in the gas phase using a low-level oxygen sensor that is accurate to at least 0.001%. The other is to measure the dO2 in your beer before and after CO2 injection. If you are measuring in the beer, use a measurement point that is furthest from the injection point so that the gas will have a chance to dissolve into the beer as much as possible before you measure. If you carbonate in a tank, just measure in the tank.

My final thought is that you may be doing everything right in the rest of your process, but if the CO2 you’re using to trim your carbonation is loaded with air, your beer may pick up a significant amount of oxygen.

Have you seen the article with the CO2 table? If you can point me to the journal and/or author, I’d be happy to post a reference.  Please leave the information as a comment below.

Frivolous Friday Fun – Ten Barrel Brew House in Ancient Egypt?

My wife Paula, an amateur Egyptologist, just brought to my attention a really cool article about a working brewery that was in full production in pre-dynastic Egypt.

So, okay — It may not match the sophistication of a ten-barrel brew house, but it looks like they could have brewed as much as 300 gallons a day. And keep in mind that this was roughly 5000 years ago – well before the first pyramid was even a glint in Pharaoh’s eye. Nice to know humans have always had their priorities straight!

Here’s the link

Guest Post by JP Camardo

Guest post by JP Camardo, Hach Marketing

Chaz has kindly allowed me to hijack the blog today. We’ve been thrilled that so many people have been finding the blog helpful and interesting. From the outset, we felt it was critical that this blog be educational and genuine above all else. The content has been great so far, and there’s a lot more coming.

In taking this brief break from our typical posts, we’re hoping you’ll allow us to do a little shameless promotion of Hach, and point out a tool for craft brewers. It’s an online interactive brochure — just launched — which you can find on our website at Hach.com/FlavorFootprint. You’ll find product information and videos on Hach’s Orbisphere products, a brewery process map with important quality parameters, a link to an online webinar, and more.

This is an incredibly exciting time to be a part of craft brewing. There is a tremendous amount of enthusiasm, innovation, attention to detail and overall quality. This was all so very evident at the recent CBC. You can practically see the passion by browsing a few snapshots from the show, not to mention all the cool events that just took place during American Craft Beer Week.  Those of us at Hach in Loveland, Colorado, were fortunate that there were quite a few ACBW activities in our area. We took advantage of as many as we could!

We hope you’ll continue to visit this blog and our website, and if you have questions or want more information, please let us know. As always, we are there to support the craft brewer’s commitment to quality.

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