Beer Forum

I'm looking into buying a compact refrigerator or chest freezer for temperature controlled fermentation and I got to thinking about the effects of all that C02 being released in a closed space. If your carboy is inside one of these units and its fermenting away, isn't there going to be some pressure inside the fridge/freezer? It's not like it's going to be a fridge bomb, but isn't there concern for additional atmospheric pressure on yeast? Is is something to think about or is it negligible? John Palmer, JZ, I'm looking in your direction.

I doubt it will be an issue.
But what do I know.
One of you propeller heads should be able to come up with volume of co2 which will be produced by an average batch... COME ON
BUB

I'm no propeller head, but I could play one on TV

I found a document at Cornell that said wine musts produce 40-50 times the original must volume of CO2. Since our beers are lower gravity than wines, I'll take that 40x to be a more likely value for us.

My 7.2ft^3 fridge is 204L. The 38L of wort I have fermenting in there will produce 1520L of CO2. 1520L of CO2 packed into 204L of space is 7.5 volumes at 68F which is way off any carb chart I've ever seen for figuring psi.

I guess the limiting factor is the seals on the seams of the fridge, and how often you open the door to have a peek.

Anyone got the ambition to figure out how much pressure a fridge or chest freezer can contain before it starts to vent?

Good question. Your correct about the CO2 build up. It's not enough to blow the door off but it's there. It depends on your seal though, an old fridge may not seal so well and release the build up. I ferment in brand new chest freezers that seal well and I have seen a rush of CO2 being released from the fermenter when I opened it. I also made the mistake of reaching in there and breathing, very painful.
Now I ferment with the manual defrost drain removed with fiberglass insulation in the hole so the CO2 can escape.
According to Jamil some pressure on the yeast during active fermentation is actually beneficial. Less ester production I believe but don't quote me on that. An airlock or blow-off hose in water puts the yeast under pressure so if your concerned about too much pressure in the freezer or fridge just vent it in some way even if it's a tiny gap in the seal.