You can make a simple fire extinguisher using baking soda and vinegar, which react to produce carbon dioxide gas that smothers small flames. This is a popular science demonstration that illustrates how real fire extinguishers work, but it’s not a substitute for a certified extinguisher in an actual emergency. Here’s how to build one, how it works, and what its real limitations are.
What You Need
The simplest version requires items you probably already have at home:
- Baking soda: about 3 teaspoons (or one-third of a cup for a larger version)
- White vinegar: roughly 50 ml (a few tablespoons)
- A jug, mixing bowl, or deep casserole dish
- A tealight candle (as your test flame)
- A safety lighter or matches
That’s the full kit. No tubing, no pressurized containers, no special sealing agents. The setup from Australia’s Questacon science center and the UK’s Centre for Industry Education Collaboration both use essentially this same list.
Step-by-Step Instructions
Set up on a flat, stable surface away from anything flammable. Place the baking soda in your jug or bowl, then pour in the vinegar. The mixture will immediately bubble and fizz. While it’s reacting, light the tealight candle and set it nearby.
Once the fizzing stops, carefully tilt the jug over the candle flame. Don’t pour the liquid out. You’re pouring the invisible carbon dioxide gas that’s sitting on top of the liquid. The candle should go out within seconds.
Here’s the clever part: carbon dioxide is heavier than air, so it pools in the container like an invisible liquid even after the fizzing stops. You can actually “pour” it from one jug into another empty jug, then use that second jug to extinguish the candle. Nothing visible comes out, but the flame dies because you’ve displaced the oxygen around it.
Why This Works
Baking soda is sodium bicarbonate. When it contacts an acid like vinegar, the reaction produces carbon dioxide gas, water, and a salt. Fire needs three things to burn: heat, fuel, and oxygen. The carbon dioxide gas displaces the oxygen around the flame, cutting off one side of that triangle.
This is the same basic principle behind real CO2 fire extinguishers. Commercial models just store the carbon dioxide under high pressure so it can be directed at a fire with force. Your jug version works gently on a candle flame but couldn’t project gas with enough volume or pressure to fight an actual fire.
Other Household Fire Suppression Methods
The baking soda and vinegar method is great for learning, but several household items can actually suppress small fires in a real kitchen emergency. Keeping a box of baking soda near the stove is an old and effective trick. Thrown directly onto a small grease fire, dry baking soda releases carbon dioxide when heated and can smother the flames.
A pot lid works on the same principle. Sliding a lid over a pan fire cuts off the oxygen supply. Fire blankets, which are made of fireproof fabric, do the same thing on a larger scale. You drape the blanket over the fire to smother it. Salt also works in a pinch, though you’d need a large quantity, and it’s slower than baking soda. Never use water on a grease or oil fire, as it causes the burning oil to splatter and can spread the fire explosively.
What a DIY Extinguisher Can’t Do
A homemade baking soda and vinegar setup can snuff out a candle. It cannot handle a real house fire, a grease fire on a stove, an electrical fire, or anything larger than a very small, controlled flame. The volume of CO2 it produces is tiny, it has no pressure behind it, and you can’t aim it.
Fires are classified by what’s burning. Class A fires involve ordinary materials like wood and paper. Class K fires involve cooking oils and fats. Class C fires involve electrical equipment. Each class requires a specific type of commercial extinguisher. A rated, certified extinguisher is designed to deliver the right agent at the right pressure for each fire type. Your science-project version doesn’t meet any of these standards.
OSHA regulations require workplaces to use only approved portable fire extinguishers. Homemade devices don’t qualify. Even for home use, a certified extinguisher (typically around $20 to $50 for a basic ABC-rated model) is the only reliable option for actual fire safety. The National Fire Protection Association recommends inspecting home extinguishers monthly to make sure the pressure gauge reads in the operable range.
Making It a Better Science Experiment
If you’re doing this as a project or demonstration, there are a few ways to make it more interesting. Try varying the amount of baking soda and vinegar to see how the volume of CO2 produced changes. Use candles at different heights inside a tall container to watch the CO2 “fill up” from the bottom, extinguishing the lowest candle first. This visually demonstrates that carbon dioxide is denser than air and sinks.
You can also test how long the CO2 remains effective after the reaction stops. Pour the gas from your jug into an empty container, wait 30 seconds, then try to extinguish a candle with it. Wait a minute and try again. At some point the CO2 will have diffused into the surrounding air and lost its concentration. Timing this gives you a practical sense of how quickly gases mix in open air.
For younger students, the key takeaway is straightforward: fire needs oxygen, and if you can separate a flame from its oxygen supply, whether with carbon dioxide gas, a blanket, a lid, or even dirt, the fire goes out. Every real fire suppression tool, from a kitchen fire blanket to a foam extinguisher on a fire truck, works on some version of this principle.