You can make carbon dioxide gas at home using a few common household ingredients. The simplest method is combining baking soda and vinegar, which produces CO2 in seconds with no special equipment. Other approaches, like yeast fermentation or dry ice sublimation, offer slower or more sustained output depending on what you need the gas for. Here’s how each method works and what to expect from it.
Baking Soda and Vinegar
This is the fastest and most accessible way to generate CO2. When sodium bicarbonate (baking soda) reacts with acetic acid (vinegar), it produces carbon dioxide gas, water, and sodium acetate, which stays dissolved in the liquid. The fizzing you see is CO2 escaping.
For a useful amount of gas, mix about one teaspoon (5 cm³) of baking soda with roughly half a cup (100 mL) of standard white vinegar. This produces approximately 2 liters of CO2 at room temperature, enough to fill a large balloon or displace the air in a small container. The reaction happens almost instantly, so have your collection method ready before you combine them. A sealed bottle with tubing running from the cap works well for directing the gas where you need it.
To get more CO2, simply scale up the quantities proportionally. The reaction is self-limiting: once one ingredient runs out, it stops. If you notice leftover baking soda sitting at the bottom, add more vinegar. If the fizzing dies down but the liquid still smells strongly of vinegar, add more baking soda.
Yeast and Sugar Fermentation
Yeast fermentation produces CO2 more slowly but steadily over hours or days, making it popular for aquarium hobbyists who want a continuous supply. When yeast consumes sugar, it produces CO2 and alcohol as byproducts.
A basic setup uses a plastic bottle with warm water, table sugar, and active dry yeast. Dissolve about two cups of sugar in a liter of warm water (not hot, which kills the yeast), then add a quarter teaspoon of yeast. Seal the bottle and run tubing from the cap to wherever you need the gas. CO2 production typically begins within a couple of hours and can continue for one to two weeks as the yeast works through the available sugar.
Temperature matters. Yeast works faster in warmer conditions, around 75°F to 85°F (24°C to 29°C). Too cold and production stalls. Too hot, above 100°F, and the yeast dies. Higher sugar concentrations, around 15% by weight, give the yeast more fuel to work with and extend the production window. The tradeoff is that fermentation setups are harder to control precisely. Output varies with temperature, sugar levels, and how healthy the yeast colony remains over time.
Dry Ice Sublimation
Dry ice is solid CO2, so letting it warm up to room temperature converts it directly into gas with no chemical reaction needed. One pound of dry ice produces about 8.8 cubic feet of CO2 gas. At room temperature, a small block loses roughly 14% of its mass per hour when left exposed, so a one-pound piece will fully convert to gas in several hours.
You can buy dry ice at many grocery stores and ice cream shops. Place it in a well-ventilated area (not a sealed room) and let it sublimate naturally, or drop small pieces into warm water to speed up the process and create a visible fog effect. Never handle dry ice with bare hands, as it sits at minus 109°F (minus 78°C) and causes frostbite on contact. Use insulated gloves or tongs.
Burning Fuel
Any time you burn a hydrocarbon fuel like propane, natural gas, or alcohol, CO2 is one of the main byproducts. This is how some commercial greenhouses enrich their air. A small propane burner or alcohol lamp in an enclosed space raises CO2 levels steadily. Natural gas produces less CO2 per unit of energy than propane or coal, roughly 55% of coal’s carbon output for the same energy released.
This method is practical mainly for greenhouse growers who need sustained enrichment over large areas and already have ventilation systems in place. For most home purposes, the open flame, heat output, and need for ventilation make it less convenient than chemical or biological methods.
Why People Make CO2
The most common reasons to generate CO2 at home are plant growth, aquarium use, and science demonstrations. For plants, the payoff can be substantial. Normal outdoor air contains about 427 parts per million (ppm) of CO2. Doubling that concentration to 800 or 1,000 ppm in a greenhouse can increase plant yields by 40% to 100% for most common crops and houseplants. Plants respond positively to concentrations up to about 1,800 ppm, but levels above that can cause damage.
For a small growing space, around 100 square feet, about one pound of dry ice per day is enough to maintain roughly 1,300 ppm. For a 200 square foot room, a 20-pound CO2 cylinder (available from welding or homebrew suppliers for $20 to $50 per refill) lasts about two weeks when maintaining 1,200 to 1,500 ppm.
Aquarium hobbyists use CO2 to promote aquatic plant growth. The yeast-and-sugar method is the go-to budget option here, since it produces a slow, steady stream that can be bubbled directly into the tank through an airstone or diffuser.
Safety Considerations
CO2 is colorless and odorless, so you won’t notice dangerous concentrations building up without a monitor. The workplace safety threshold is 5,000 ppm for an eight-hour exposure. At 30,000 ppm, even short exposure causes headaches, dizziness, and shortness of breath. At 40,000 ppm, the environment is immediately dangerous to life.
For context, normal air is about 427 ppm, so you’d need to displace a significant amount of room air to reach dangerous levels. But in small, sealed spaces like closets, tents, or poorly ventilated rooms, this can happen faster than you’d expect. Keep a window cracked or a fan running whenever you’re generating CO2 indoors, especially with combustion or dry ice methods. If you feel lightheaded or short of breath, leave the area immediately and ventilate it before returning.
If you’re running a pressurized CO2 system from a cylinder, make sure your regulator is rated for CO2 and check all fittings for leaks. A simple way to test is to note the gauge reading after you close the cylinder valve. If the high-pressure gauge slowly drops, gas is escaping at the connection point.