Fire pits are often considered an inviting part of outdoor spaces — but sometimes the smoke they create is less than inviting. Whether the lingering smell on your coat or in your hair is a nuisance, or you happen to be the person who always seems to be sitting where the wind blows the smoke, reducing the amount of it can improve the quality of your evening around the fire. Although there’s no such thing as a completely smokeless fire, so-called “smokeless” fire pits use a double-chamber system for fuel burning that outputs significantly less smoke.
How does a smokeless fire pit work?
A smokeless fire pit works is by circulating air through a double-walled container that a fire can be built in. First conceived of by the Dakota people, this simple and ingenious engineering trick can be mimicked in our contemporary fire pit designs by either modifying an existing backyard pit or building a new one.
The air gets heated as it travels through the outer wall, and more of the fuel is burned at this higher temperature, causing less residue, ash, and smoke to be emitted. The downside is that a hotter fire will tend to send heat upwards faster than it goes outwards, so it doesn’t have as much radiant heat as a traditional fire pit; but it still has the dancing flames and warm light, and you will still feel some heat from the fire.
What you need to make a smokeless fire pit
For this project, you’ll need:
- Adrill with a metal drill bit
- Either an existing fire pit with a metal ring or a 20-quart and a 16-quart pot (plus a lid for the 20-quart pot)
- A jig saw with a metal blade
- A sturdy pair of metal shears or a grinder (to build a new smokeless fire pit without the stone structure)
- A metal file (to dull the edges of your holes and cut metal pieces)
- A heavy pair of metal working gloves
- Safety goggles
- Ear protection
How to modify an existing traditional fire pit
For your existing pit, remove the metal ring from the pit and widen the base so it lays about an inch from the outside of the metal fire pit ring — leaving about enough space for your finger to fit between the outer wall of your pit and the ring is enough to allow air to travel around the outside of it.
Once you have your first layer of stone or brick laid, you’ll need to create some spaces to allow air to flow into the gap. Some people gap their stones at the base to make an intake hole about every foot or so around the circumference of your pit. If you’re using bricks, you can use a half brick with a space to each side of it every second or third brick. Then you can rebuild the outer wall of your fire pit with no gaps.
Next, you’ll need to drill holes in the fire pit ring. Use your drill and metal drill bit to drill a hole about every foot, about an inch from the top edge of your metal ring. You should use your safety gear for this part to prevent metal splinters. Use your file to smooth out the edges of the holes you drilled and remove any barbs left over. Place your ring back into your fire pit, and you’re all set.
How to build a new smokeless fire pit
To build a new metal smokeless fire pit, take the lid of your 20-quart pot and use the bottom of your smaller pot to trace a circle in the centre of the underside of the lid with a permanent marker. Don your safety gear and use your grinder with a cut-off blade, drill, and jigsaw with a metal blade (or drill and metal shears) to cut out the middle of the larger pot’s lid. Use the file to smooth out the edges of your hole, and your smaller pot should nest in the lid of the larger pot, leaving about a one inch gap between the two.
Next, drill holes every three inches or so, an inch from the top of the smaller pot and an inch from the bottom of your larger pot. Use your metal file to remove any barbs and smooth the edges of the holes. Then, when you put the two pots together, you’ll have a small smokeless stove. Make sure that when you use your stove, you’re not placing it on a surface that’s vulnerable to heat so you don’t start a fire outside your pit.
This method will work with any pair of containers with a similar ratio in size to a 20- to 16-quart ratio. For a larger model, metal trash cans will work, as well.