Early on co2 can cause major problems in your base, dupes can only breath oxygen and will suffocate in co2 environments they can’t escape from.
Fast fixes
Early game, dig out an area beneath your base. Co2 sinks below oxygen, so it will flow down into lower areas. That will give you time to deal with it later. Next make sure you have oxygen generation, if you have Algae then use an Oxygen Diffuser (if not then you’ll need to setup an Electrolyser). Avoid carbon skimmers for now as power generation creates lots of co2.
Turn off things that generate co2. Turn off that Coal generator, and reduce energy usage as much as possible. You can power an early base with a 1 or 2 manual generators and limiting machinery use to essentials.
Early co2 removal can be done with Oxyferns and algae terrariums. Use these to allow time to build better options. Once you’ve managed to find some breathing room the next step is to store, use or destroy.
Fixing the problem
Storing co2 is not recommended, as it’s easily produced and you will have a lot of it. So what are the options?
Pump it out into space
Dig up until you reach space, connect a pipe from a gas pump at the bottom of your base. The co2 will quickly vent out into space. Until you have automation setup, you’ll need to remember to turn the pump on/off when you need to clear out more co2.
Using It
There are a few farms that require co2.
Mushroom farms are easy enough to build, mushrooms use co2 and provide the benefit of food.
Slickster (critter) farms produces oil and consume large quantities of Carbon Dioxide, however this generally only an option later in the game.
Common Options
Carbon skimmers are the stable option if you have water and power. They have the benefit of not requiring any attention once setup, but do consume ongoing power and require polluted water treatment. The problem with most power options is that you could be adding to your carbon dioxide problem.