Country Lore: How to Achieve a Clean, Top-Down Burn

Readers' tips on burning clean fires, deterring voles, freezing berries, and more.

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by Richard Ehrenberg
Changing the direction that each layer of splits faces creates pockets that allow air to travel through.

Burn Clean

Burning wood often releases a lot of toxic chemicals and dangerous gases into the atmosphere in the form of smoke. The majority of that smoke release occurs when starting and adding wood to a fire. Typically, people start fires by burning the bottom of stacked wood, so the heat warms and ignites the wood above as it rises. However, this method causes more smoke to escape and pollutes the atmosphere. There’s a much cleaner way to ignite a full fire.

Smoke is the result of a process called “pyrolysis,” whereby heat — not flame — chemically alters molecules in the wood, turning them from a solid into a gas filled with burnable substances. If the flames of the fire don’t ignite these gases and substances, they go up the chimney in smoke.

To reduce smoke pollution when starting a fire, light the fire at the top of the stacked wood, and allow the flame to travel downward. This reverse burning process initiates pyrolysis in the wood within and below the flames of the fire. As the smoke below rises, it passes through the flames, which ignites the burnable substances in the smoke. The substances that remain to flow up the chimney are CO2, water vapor, and heat. Not only does this reduce the smoke from a fire, but it also releases additional heat in the fire.

To achieve a good top-down burn, carefully place each layer of wood splits at a 90-degree angle to the layer beneath. Place the largest splits on the bottom layer, and use smaller splits for each succeeding upper layer. When stacking these layers, leave small spaces between each split; this creates pockets that allow air to freely flow upward. Build the top two layers out of kindling, leaving adequate air space between each piece. Finally, place two to three crumpled pieces of paper on the top, and light the papers. Too much paper will leave behind sheets of carbon that block airflow.

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