If you live or sleep in the same room where you keep the fermenter, it could mean there are abnormal levels of Co2 in the room you inhibit and after all Co2 replaces oxygen making it harder to breathe.
Fermentation is a fun part of brewing when you delegate the work to billions of yeast cells which produce the wonderful homebrew out of the sweet mess we created on a brew day, but could it also be dangerous?
Fermenter fumes (Co2) from fermenter are not dangerous as long as there is air ventilation of some kind, but even if Co2 accumulates in a small room without air filtration it’s extremely unlikely to cause death of human or a pet. Yet, even slightly abnormal levels of Co2 could cause headaches and fatigue if you spend enough time in a room.
Does this surprise you? Have you slept in a room with a fermenter by your side before and experienced anything suspicious?
Yeast eats sugars and produces lots of Co2 that gets pushed through airlock as if the gas were to stay in the fermenter, the things could get messy if it explodes. So, We are dealing here with lots of Co2 that leaves fermenter bucket and the Co2 slowly fills the room.
This question bothered me and some people I know, so I had to make a research to see is there a real dangerous to our health.
Is Co2 dangerous?
Co2 is dangerous to humans only in high levels and it’s difficult for Co2 levels to reach the critical point in larger rooms or rooms with normal air ventilation such as having an open window or doors to a nearby room.
As the levels of Co2 rise, the oxygen gets replaced and the environment becomes hostile for humans and pets.
If the levels of Co2 in a closed room exceed 5000 ppm it could cause signs such as headaches and fatigue already after a couple of hours, if the levels would get above 20 000 ppm and you slept in the room for more than a few hours it could cause something close to Co2 poisoning and you would feel extreme headaches, fatigue and nausea. Yet only at 40 000 ppm the Co2 replaces oxygen to the point where it could kill a person.
The Co2 is heavier than air, so higher volumes would be found on the floor than in the height of a bed.
How much co2 does fermentation produce?
Average 5 gallon fermenter produces close to 2 pounds of Co2 in 24 hours, compared to this humans exhale 2.3 pounds of Co2 in 24 hours.
Of course, things like attenuation play a big role in how fast and how much Co2 is produced but it won’t get far from the mentioned average.
This volume will hardly exceed 1000 ppm unless the room is super small (like 4×4) and you don’t ventilate it for more than 24 hours. The small signs of headaches can already occur at 1000 pm if you spend like 12 hours in the room.
It’s obvious that we produce more Co2 than a fermenter and if you ever spent a day in a small room with poor ventilation with a couple of friends, you may have noticed how it gets harder to breathe, so you need to catch some fresh air before minor headaches kick in.
The clear picture is that a single 5 gallon fermenter can’t hurt you, but if you sleep in the 4×4 room with an active fermenter for 8 hours without any air ventilation it could cause minor headaches and fatigue when you wake up, just as you could produce that extra Co2 on your own if you wouldn’t ventilate the room.
Now, the real issue is if you brew multiple homebrews in the room as this could get the Co2 levels pretty high. If 1 fermenter produces almost as much as a person in 24 hours, imagine being in a small room without ventilation with 10 people.
Final take on
I have heard stories of people complaining about headaches the next morning after they would sleep with fermenter in a room without air ventilation during winter as opening a window would mean a bigger problem.
Unless you have a real small factory in your room I wouldn’t be afraid of Co2 levels getting so high that you would feel serious consequences of Co2, but even with a fermenter or two you should provide the room with enough air circulation because the levels can accumulate over night and even the minor headaches and fatigue isn’t something you want.