Wondering how to make a DIY smokeless fire pit? We were too! Learn how we used a battery-operated blower to dramatically decrease the amount of smoke our fire pit produces—no engineering degrees required.
This is a guest post from my husband Mike. He does a lot of projects that don’t make it to the blog, but I had to share this one. Enjoy it!
Our attempt at a DIY smokeless fire pit
We recently left townhouse living and found ourselves with more yard space than we knew what to do with. Naturally the first order of business was getting a fire pit set up. While my wife loves the smell of fire pit smoke, I can’t stand it.
So the research began. I started with YouTube for some quick and dirty inspiration. That is where the rabbit hole began. What the hell is a smokeless fire pit and how can I make one for myself?
If you haven’t checked out some of the designs, they consist of a normal looking fire pit metal ring but with specifically placed drill holes for air intake. The “how” of it all was beyond my comprehension, but Jon Chan gives a great description in the first 2 minutes of his video for anyone still curious.
To my surprise you can even buy these pits now prefabricated (at a much higher, non-DIY price) on Amazon or your local Home Depot or Lowes. But you’re here because you like to DIY.
Why is my fire pit so Smokey?
But why are fire pits so smokey to begin with? In a fire, smoke occurs when there is not enough oxygen. It’s called “incomplete combustion.” So forcing oxygen to the combustion site (the fire) helps decrease the amount of smoke it produces.
It’s also worth noting that there are other things that can lead to a smokier-than-average fire. Don’t ask us how we know that burning 10-year-old dead wood leads to a lot of smoke. Wood that is not fully dried/seasoned can also lead to more smoke. The tutorial here assumes the use of properly dried firewood.
How do you make a smokeless fire pit?
As it happened, I was recently visiting an old friend over the weekend (shout out to Headberg5000) who is a mechanical engineer. He makes some amazing stuff, so he was a great person to bounce some ideas off of.
He explained it is a matter of forcing fresh air (oxygen) into the burn site (the wood down below). When he got out the leaf blower to illustrate this using his own (non-smokeless) fire pit, I knew that he was onto something.
The leaf blower also continuously stoked the flames, making it easier to ignite and maintain the fire. And it also provided a raging inferno with minimal smoke.
Many of the tutorials I’d seen online simply drilled a few holes into a steel fire pit ring to help with air circulation, mimicking a similar leaf blower effect on a much smaller scale. However, Headberg5000 showed me that a few drilled holes were no longer on the menu.
The next step was to find a middle ground between a 40-volt hurricane (the leaf blower) and passive air intake (the drilled holes).
How do I make my fire pit smoke less?
As a full disclaimer, I don’t know that a DIY smokeless fire pit will ever be 100% free of smoke. Therefore, our main goal is to minimize smoke as much as possible using air—to make the fire pit smoke less.
I found a tutorial online that used an underground system with a 12V bilge air blower and several HVAC parts. I loved the look and design; however, once constructed I found that the underneath airflow was minimal at best and had no effect on the fire trials.
The design required pavers and gravel on top of the air outtake, so there simply wasn’t enough direct airflow to make a noticeable difference. You can take a look at the series of six pictures below to see an overview of this first attempt.
Although I liked the underground bilge blower system, I found that I needed more leaf blower like power. I found the best solution to be a partially submerged direct blower system, which I will describe in detail for this tutorial.
Here’s what I used:
(This was a very extensive project, and I’ve tried my best to make sure I included everything I used. A few smaller things like miscellaneous screws and washers might not be mentioned below.)
- Sunnydaze Steel Outdoor Fire Ring Insert
- Master Flow Round Metal Duct Pipe
- Galvanized Steel Worm Gear Clamp
- Dryer Vent Installation Duct Tape
- Master Flow Round Duct Cap
- HDX27 Gallon Tough Storage Tote
- IRONFACE Adapter for DEWALT 12v Max Battery
- 12V Lithium Ion Battery
- Aluminum Flexible Dryer Vent Hose
- SEAFLO 4″ in-Line Marine Bilge Air Blower
- Round Grate, 4-Inch
- Scrap 2×4, see step 2 for purpose
- Large pavers
- Utility knife
- Drill and a large bit
- Dremel and appropriate bits—or something else than can cut through the steel fire pit ring
And here’s how I attempted our DIY smokeless fire pit.
Step 1: Dig the hole and trench
Digging the hole for the fire pit and the trench for the piping turned out to be the unexpectedly hardest step. It turns out that our backyard is no more than 3 inches of dirt on top of a million huge rocks. But once all the rocks were muscled out, laying the ventilation system was pretty simple.
Our sizing/measurements were as follows:
- 36-inch diameter pit area for the metal pit ring dug approximately 6 inches down
- Trench out from the pit area approximately 6-8 inches deep and wide; the length of the trench depends on how far you want your mechanical box to be, and ours is about 7 ½ feet total (about 3.5 feet from the pit to the mechanical box and the rest from the mechanical box to the air intake)
Note that the materials list has a 5-ft duct pipe, but we cut ours down to about 3 ½ to meet the mechanical box.
The mechanical box with the blower will be at about the center of the trench. The mechanical box is really just a fancy way of saying “a heavy duty plastic tote with a removable lid.” You’ll see it in the photos below.
Based on the size of our mechanical box, we needed to dig down about 16 inches to ensure it was completely buried. We also needed to widen the trench a bit only in this area to accommodate the box.
Note that while we have approximately 3 feet from the mechanical box to the air intake, it could be anywhere from 2-7 feet. It’s based on the length of the dryer hose you use.
Step 2: Set up the mechanical box with the blower
Once I finished the groundwork, I worked on the mechanical box. I mounted a small piece of 2×4 to the bottom of the tote using a couple bolts and washers. I added this 2×4 to stabilize and align the blower and also to raise it off the bottom of the box in the event some water gets in.
After using this a few times and having a few rains, I also ended up drilling a few small drainage holes in the bottom of the plastic box to help get rid of any excess water that snuck in (it was only a little bit, but I didn’t want it sitting in there).
Once the 2×4 was in place, I attached the blower with a couple screws. Note where the blower intake and outtake are aligned on the tote and cut out circles for the piping between 4-5 in in diameter. (Cut these circles out of the sides of the box–I just used a utility knife.)
If you haven’t toyed with it already, you can test out the power supply. Simply connect the blower’s lines with the 12v power connector using a couple winged wire connectors.
Step 3: Assemble pipe, duct, and mechanical box
Now you can start getting the big pieces together (which you may have already noticed in some of the previous pics). Add the mechanical box to its dug-out location. Remember that you’ll need to be able to access and remove the lid when you use the pit.
Lay out and align the metal duct pipe and the dryer vent hose to the blower intake/outtake. At this point, if you haven’t already, you will customize the length of each and cut down to size if necessary.
You’ll want the duct pipe to be sticking into the fire pit a couple inches (we also used a few bricks to support this). Then attach the duct cap (see photo below) and start drilling in all the air holes. Enough to provide significant air current but not too big that debris could easily fall in.
Now angle up the dryer vent hose and attach the drain grate–the area where air will enter the system. All attachments used either a steel worm gear clamp or the installation duct tape (sometimes both).
Step 4: Fill the trench and finish the fire pit
Because the duct pipe extends slightly into the bottom of the fire pit ring, you’ll need to cut out a semi-circle along the bottom of the ring. The semi-circle should be sized to fit the pipe/duct cap.
I used a Dremel to do this, but fair warning that I went through four or so blades. If you have a better tool for this, definitely use it. Gently place the fire ring back down and fill in with gravel or other pit filler of your liking.
Once everything is attached and in place, you can start filling in the trench. This stage will take some customization and finesse. Add back some of your fill dirt/big rocks to get the piping snug on each side. Top off the trenches with the grass patches removed earlier.
The areas dug out for the piping shouldn’t support direct standing weight; therefore, we laid out a pathway of wide pavers that extend several inches beyond either side of the trench to protect the area and distribute the weight (the large white tile-looking pavers you’ll see in the finished photos).
After this, we dug out additional space around the pit and on either side of the wide pavers to add some rock landscaping. This is purely aesthetic though and is not a necessary step to enhance air flow.
Step 5: Get the fire going!
Once we were ready to test our fire, I hooked up a 12V lithium ion battery to power the blower. I chose this battery method for easy charging purposes because it lasts a long time and can be easily charged on the chargers we already have for our battery-operated tools.
This is why it’s important that you can always access the mechanical box. We simply remove one of the large tile-like pavers and then remove the lid to the mechanical box to add the battery to the blower’s dock.
In the future, I’d like to hook up a remote control system so that I only have to access the mechanical box when the battery dies. But I haven’t quite cracked that nut yet, and I will update this post when I do!
Our finished DIY smokeless fire pit
There you have it folks. Here are a few pictures Brit took while we were out roasting marshmallows one night. It’s very hard to capture the presence or absence of smoke in photos, but these show it pretty well.
The first is a fire without the blower turned on, while the second and third have the blower turned on.
I also want to note that you will hear the blower while you’re using the fire pit. It doesn’t really bother us, and the sound is muffled from the mechanical box, dirt, and pavers. If you do think the noise would be bothersome, you could always extend the vent hosing out further, but that means more digging.
You’ll find that there is a lot of room for customization and modification depending on your setup. This is just the approach we took for ours, and we’re happy with how it turned out. Hopefully you find some inspiration from this project.
Let us know if you have any questions or require more clarity on any particular stage. Keep the fire burning!