Professor Green wrote:OK I'll try this again in the hope that we can actually have a sensible discussion about this given that CO2 is dangerous.
Too much of anything is dangerous. The key is understanding the hazardous quantity involved relative to the physiological or toxic effect as a function of concentration/dose.
According to this piece of reasoning:
https://lifefermented.wordpress.com/2014/01/22/how-much-co2-is-produced-from-brewing/a 20'ish L brew generates around 450 L of CO2. Quantities will vary depending on the amount of sugar that the yeast has available to munch on and other relevant factors.
Evolution of CO2 occurs over time:
https://homebrewjournals.com/how-long-do-you-brew-beer/So, a 1 - 2 week timeframe (depending), noting that CO2 generation will be more vigorous in the early stages of the process. The point being that the generated CO2 doesn't discharge to atmosphere at the snap of your fingers. However, if the fermentation is taking place in a small, gas tight space (fermentation fridge?) or a room with little ventilation, then CO2 levels will be a concern.
From the info available above, it's possible to derive a rough estimate of the daily CO2 production and factor that in to dimensions of the space used for fermentation and how open it is to the outside world. How often does the room get traffic where doors are open/closed that mixes up the air in the room? What kind of forced ventilation is typically operating, e.g. a fan? What about natural ventilation? Or an open window? From that, an understanding of how risky the work space is can be gauged.
Note that one comment above mentions that CO2 is denser than air, so it will tend to slump and will not be buoyant. So, I'd agree that brewing / fermenting in a basement is not ideal. The upside is that you can walk into a slumped cloud of CO2 and, so long as the cloud volume isn't excessive, your mouth can breath clean air. You'll have a problem if you decide to lie down for some reason though. And if you've got a dachshund, then keep them out of your workspace for their own health.
Physiologically, CO2 triggers the body's breathing response:
https://en.wikipedia.org/wiki/Carbon_dioxide#Human_physiologySo, a clue that you're in an environment with excessive CO2 levels is that your breathing rate will increase above normal.
Please don't confuse CO for CO2, the former is seriously toxic:
https://en.wikipedia.org/wiki/Carbon_monoxide#Toxicityand can lead to the kind of nasty experience that howard relates.
All that leads me to expect that for DIY production quantities, CO2 is probably not a significant concern for the majority. Even so, there are always exceptions and understanding the relevant physics is a good way to avoid being caught out.
Thanks to Prof Green. This thread has been a handy thought exercise.