Do Smokeless Fire Pits Really Smoke Less?
December 8, 20224 min readWalden Backyards
Nothing that burns wood is smokeless. That word is the one part of the pitch that was never true, and it has sold an enormous number of fire pits. The engineering underneath it is real, though, and it is a good deal simpler than the advertising makes it sound.
What a smokeless fire pit is actually doing
Smoke is fuel that did not finish burning. Wood gives off gases as it heats up, and if those gases never get hot enough, or never meet enough oxygen, they leave the fire as visible smoke instead of turning into flame and heat.
A double wall fixes that with no moving parts. Air enters through vents near the bottom, climbs the gap between the inner and outer wall, and comes back out hot through a ring of holes near the top, right where the unburned gases are sitting. Those gases get a second chance at combustion. Burn the smoke twice and much less of it reaches your face.
No fan. No battery. No app. A wall, a gap, and a row of holes in the right place.
So why is the word still wrong
Because it promises an absolute, and fire does not deal in absolutes. Several things will put smoke back into even a well designed pit:
- Wet or green wood. The water has to boil off before the wood can burn properly, and while that is happening you get steam and smoke. No design outruns bad fuel.
- Too much wood at once. Smother the airflow and the secondary burn quits working.
- Ash piled up over the lower vents. If air cannot get in low, nothing comes out hot up top. Clean it out.
- Softwoods like pine and cedar. More resin, more smoke, whatever it is burning in.
Our guide on how to build a smoke free fire covers the fuel side of this properly. Good design and good wood together get you most of the way there. One without the other does not.
The question actually worth asking
It is not whether the second burn works, because it does. It is whether you should have to buy a whole new fire pit to get it.
Most smokeless pits on the market are standalone bowls. You buy the entire object, you set it on the patio, and the stone or block pit you already paid someone to build sits there not being used. That is the part that is marketing. The technology is a wall and some holes. It was never married to a portable bowl.
The same second burn, in the pit you already own
An insert puts the double wall down inside the opening you already have. Measure the inside of the pit at its widest point, then drop it in.
The Comfort II insert set is a double wall bowl working on exactly the principle above, with a 24 inch or 32 inch firebox, fitting openings from 27 to 44 inches in round or square. It comes with a snuffer lid sized to it, so you can smother the fire at the end of the night and keep rain and leaves out of the bowl until the next one. Nothing to assemble. Hand built in the United States from heavy gauge steel.
A firebox that size matters more than it sounds. The portable bowls are small out of necessity, because someone has to be able to pick one up and carry it. A pit built into the ground has no such limit, and wanting a bigger fire is usually why people built one in the first place.
There is a second reason to line a masonry pit, and it has nothing to do with smoke. Direct flame and radiant heat against block is what opens up mortar joints and spalls the face off manufactured stone after a few seasons. On a lot of block products, running an open fire against it voids the manufacturer warranty. A steel liner, with a brim that rests on the stone and overlaps the lip of the opening, keeps that heat off the masonry you paid for.
If you want the second burn for less money, the Mojo is a six piece stainless liner for round openings 27 to 34 inches across. It assembles inside your pit in a few minutes with no tools, and it ships in one small box. No lid and no floor with that one, but the same idea doing the same work.
What to do if you are not buying anything
Quite a lot, actually. Burn dry hardwood, so oak, ash, beech or hickory. Season it properly or buy it kiln dried. Lift the wood up off the base on a fire grate so air feeds the fire from underneath instead of only around the edges. Keep the ash cleared out. Add wood a little at a time rather than stacking the thing full. And get air where it needs to go with a Stoker Poker instead of leaning into the heat and blowing on it.
None of that costs anything beyond the firewood, and it does more than most people expect.
Luxury Firepits - Firepit Accessories - Firepit Grates
Walden Backyards Makes the Highest Quality Fire Pits and Accessories
Fire Pit Insert Set - Blow Through Stoker Poker - Fire Pit Grates - Accessories
