DIY Smokeless Fire Pit: A Step-by-Step Guide to a Cleaner Burn

Enjoying a crackling fire in your backyard is a timeless pleasure, but the smoke often detracts from the experience, irritating eyes, and leaving your clothes smelling like a campfire. Fortunately, you can significantly reduce smoke with a well-designed fire pit. This article will guide you through the process of building your own smokeless fire pit, detailing the steps, materials, and techniques involved. We’ll cover the science behind smokeless fires, different construction methods, and safety considerations to ensure you have a great experience. Let’s dive in!

Understanding Smokeless Fire Pits

Before we start building, it’s helpful to understand why traditional fires produce so much smoke and how smokeless fire pits mitigate this. The key lies in achieving a more complete combustion of the wood. Here’s a breakdown:

• Incomplete Combustion: Traditional fires often suffer from incomplete combustion. This occurs when the wood doesn’t receive enough oxygen or when the fire temperature is too low. Incomplete combustion leads to the release of unburned fuel particles, including smoke, creosote, and other pollutants.
• Secondary Combustion: Smokeless fire pits promote secondary combustion. This means that the smoke, or unburnt fuel, is re-ignited. This is usually achieved by creating an environment where preheated air is introduced into the burning chamber above the initial flame. This higher temperature environment allows the smoke particles to burn off, reducing smoke output significantly.
• Key Design Elements: The primary design elements that facilitate secondary combustion in smokeless fire pits are:
• Double Walls: The most common feature of smokeless fire pits. Double walls create a channel where air is drawn in, heated, and then released above the fire.
• Air Intake Vents: Strategically placed vents at the bottom allow air to enter and feed the primary fire.
• Secondary Air Jets/Holes: Located at the top of the inner wall, these jets or holes allow the preheated air to mix with the smoke, initiating secondary combustion.

Types of Smokeless Fire Pits

There are a few different ways to create a smokeless fire pit, each with its pros and cons. The following are the two main types we will focus on:

1. Double-Walled Metal Fire Pit (DIY): This is the approach we will take for our guide. This method typically uses steel and requires some welding or cutting. However, with some care and the right tools, this project is achievable for most DIY enthusiasts. These fire pits are relatively efficient in burning fuel.
2. Modified Fire Pit: This is more of a modification of existing fire pits. This typically involves adding a secondary ring with air holes. This method is less robust but is more affordable and easier to implement if you already have a fire pit.

Materials and Tools

Before beginning, ensure you have the following materials and tools on hand:

Materials for a Double-Walled Metal Fire Pit

• Steel Sheets: You will need steel sheets for both the inner and outer walls. 1/8” (3mm) steel is recommended. The exact size will depend on the size of your fire pit. For a small fire pit, you might need two 2ft x 4ft sheets. If you have scrap, it can reduce your materials costs.
• Steel Tubing or Angle Iron: For creating a spacer between the inner and outer wall, these are used for the rim of both walls as well. They can be 1″ or 1.5″ wide and 1/8″ thick. (4-12 ft total)
• Welding Rod or Wire (if welding): Choose the appropriate rod or wire for your welding machine and steel grade.
• High-Temperature Paint: For protecting the metal and giving it a nice finish.
• Optional: A grate to hold up the wood.

Tools

• Welding Machine (if welding): MIG, TIG, or stick welder.
• Angle Grinder with Cutting Discs and Grinding Wheels: To cut the steel sheets and clean the welds.
• Measuring Tape and Ruler: For accurate measurements.
• Marker or Soapstone: For marking your cut lines.
• Welding Clamps: For holding pieces together while welding.
• Personal Protective Equipment (PPE): Safety glasses, welding helmet, gloves, and hearing protection are crucial.
• Metal File or Deburring Tool: For smoothing sharp edges.
• Drill with metal drill bits: For drilling holes for air intake and jets.
• Optional: Metal Shears or a Plasma Cutter if you plan to skip the grinder for cutting steel.

Step-by-Step Instructions for Building a Double-Walled Smokeless Fire Pit

This detailed step-by-step guide will lead you through the process of making a double-walled smokeless fire pit from scratch. Remember to always prioritize safety and wear the appropriate PPE.

Step 1: Planning and Design

• Determine the Size: Decide on the desired diameter and height of your fire pit. A common size is 24-30 inches in diameter and 12-16 inches in height, but your decision will depend on your personal preferences and available space.
• Create a Sketch: Draw out your design, including the dimensions of the inner and outer walls, the spacing between them, and the placement of air intake holes and secondary air jets. For example, if you decided to have a 24″ diameter pit, plan for about a 2″-3″ gap between the inner and outer walls. The inner wall can be 12″ high and the outer wall can be 14″-15″.
• Calculate the Materials: Using your design, calculate the amount of steel you will need. Remember that circles need pi in the math to calculate circumference and surface area. The circumference is the measurement used to cut the steel. (Circumference = 2 * Pi * Radius, or Diameter * Pi; Surface Area of a cylinder = 2 * Pi * Radius * Height. Do this twice, once for the inner cylinder and once for the outer.)

Step 2: Cutting the Steel

• Mark the Steel: Using your measurements, mark the cut lines on your steel sheets using a marker or soapstone. Be precise in your markings to ensure the pieces fit together properly. For example, if your calculations said the inner wall needs a circumference of 75.39 inches, then mark a line that long. If you have a 12″ height, mark that along the 75.39″ line.
• Cut the Steel: Carefully cut the steel using your angle grinder with a cutting disc or a plasma cutter if you have one. Follow your marked lines and take your time. Cut straight and smoothly. If using an angle grinder, cut in several passes to not overheat the steel.
• Deburr the edges: The edges of the freshly cut steel can be sharp. Remove burrs and smooth all the cut edges with a metal file or a deburring tool.

Step 3: Forming the Inner and Outer Walls

• Form the Cylinders: Take the cut steel sheets and form them into cylinders. You may need to use clamps or a helper to maintain the cylinder shape.
• Tack Welding: Tack weld the seams together. Tack welding is basically spot welding, done at regular intervals to keep the pieces aligned. You should still be able to adjust them slightly at this stage.
• Complete Welding: Weld the seams completely. Weld from the outside of the cylinder first, then clean the weld. Then do a second weld on the inside of the cylinder. Be sure the welds are continuous to make a solid seal and reduce air leaking. Ensure the weld is free of major flaws like pinholes.
• Grind Down Welds: Use the angle grinder with a grinding wheel to smooth down the welds. This will provide a cleaner look and feel. Be careful not to remove too much of the weld.
• Repeat for Both Walls: Repeat this process for both the inner and outer walls.

Step 4: Creating the Base (Optional but Recommended)

• Cut a Circle for the Base: Cut a circular piece of steel that will serve as the base of your fire pit. This should have the same diameter as your outer cylinder.
• Tack Weld the Base: Tack weld the outer cylinder to the base, ensuring it is centered.
• Complete the Base Weld: Fully weld the base to the outer cylinder from the outside, then go inside and weld the base to the cylinder from the inside. Again, this should be a continuous, leak-proof weld.
• Grind Down Welds: Grind and smooth the welds as you did before.

Step 5: Adding Spacers and Secondary Air Jets

• Cut Spacers: Cut the steel tubing or angle iron to the appropriate length to fit around the top and bottom edges of the outer and inner cylinders.
• Tack Weld Spacers: Tack weld the spacers around the top and bottom of the inside of the outer cylinder.
• Add the Inner Cylinder: Insert the inner cylinder inside the outer cylinder, placing it on the spacers.
• Adjust Spacing: Adjust the spacing between the two cylinders, using measuring tape, to ensure it is consistent and according to your plan.
• Tack Weld Inner Cylinder: Tack weld the inner cylinder to the spacers at multiple points.
• Complete Welding Spacers: Finish welding the spacers to the inner and outer cylinders.
• Drill Secondary Air Holes/Jets: Carefully drill the secondary air jets around the inner wall, just below the top edge. These should be small and strategically placed. Common placement includes spaced holes every couple of inches. Experiment to find what works best for you. This is a critical step for creating the secondary combustion and the smokeless operation.
• Drill Air Intake Holes: Drill larger air intake holes at the bottom of the outer wall. You may wish to include 3-4 holes around the base of the outer wall.

Step 6: Finishing Touches

• Grind Welds Again: Smooth all the welds one last time.
• Clean the Metal: Thoroughly clean the metal surfaces with a degreaser and a clean cloth, removing any dust, oils, or residue.
• Apply High-Temperature Paint: Apply at least two coats of high-temperature paint to the entire fire pit, inside and out. Ensure to follow the instructions on the paint can and allow enough time to dry before using the fire pit.
• Optional: Add a Grate: A metal grate placed at the bottom of the inner wall will allow better air circulation and help prevent the wood from smothering the fire.

Safety Considerations

Safety is paramount when using any fire pit. Follow these guidelines:

• Location: Place your fire pit on a non-combustible surface, away from structures, trees, and flammable materials.
• Clear Area: Keep the area around the fire pit clear of debris and vegetation.
• Water Source: Always have a water source nearby, such as a hose or bucket of water, in case of emergencies.
• Never Leave Unattended: Do not leave the fire pit unattended. Someone should be responsible for monitoring it at all times.
• Mind the Weather: Avoid using the fire pit during dry, windy conditions.
• Use Proper Fuel: Only use dry, seasoned wood. Avoid using materials like plastic, cardboard, or chemically treated wood.
• Cooling Time: Let the fire pit cool down completely before storing or moving it. Embers can stay hot for a long time.
• Know your local regulations: Some jurisdictions prohibit or have regulations about open fires. Check local ordinances before use.
• Use fire-resistant gloves: Use fire-resistant gloves when handling the hot fire pit, or adding wood to the fire.

Tips for a Smokeless Fire

• Start Small: Start your fire with a small amount of kindling and gradually add wood.
• Use Dry Wood: Dry, seasoned wood burns much cleaner and produces less smoke. Green or wet wood releases a lot of moisture which contributes to smoke.
• Proper Wood Arrangement: Stack the wood in a way that allows air to circulate freely. Don’t pack it too tightly.
• Maintain Temperature: Maintain a good, hot fire. Low-temperature fires tend to produce more smoke.
• Avoid Overloading: Don’t overload the fire pit with wood. Adding too much wood at once can smother the fire and lead to more smoke.

Conclusion

Building your own smokeless fire pit is a rewarding project that enhances your backyard experience, reduces smoke, and is more eco-friendly. While it requires some effort, the result is a more enjoyable and clean fire experience. By following these step-by-step instructions, understanding the principles of smokeless combustion, and prioritizing safety, you can create a fire pit that will last for years to come. Now you can sit back, relax, and enjoy the warmth of your new smokeless fire pit without the bothersome smoke. Happy building, and happy fires!