What Wood Not to Burn in Your Fireplace: The Ultimate Safety List (2024)
Expert Guide | Safety & Maintenance
The fireplace is the heart of the home during winter. But unlike a gas furnace, a wood-burning system relies entirely on the quality of the fuel you feed it. Many homeowners mistakenly believe that “wood is wood.” This misconception leads to thousands of structural fires every year.
In this guide, we will detail exactly what wood not to burn in a fireplace, the science behind why, and the safe alternatives to keep your home warm and secure.
Table of Contents
The “Never Burn” List: Toxic & Dangerous
These materials should never enter your firebox. They release toxic chemicals, heavy metals, or burn at temperatures that can damage your masonry.
Lumber treated for outdoor use (decking, posts) is infused with chemicals like arsenic or copper. Burning this releases highly toxic fumes into your home and neighborhood.
Old paint may contain lead. Varnish and stains release chemical toxins when incinerated. If you are remodeling, discard the trim; don’t burn it.
Wood found on the beach is saturated with salt. When burned, the salt becomes corrosive, eating away at metal dampers and liners. (See: fixing leaky chimneys).
These are engineered woods held together by high-strength glues and resins. Burning them releases formaldehyde and carcinogens. Save these for the landfill.
Also, avoid burning household trash. Pizza boxes and wrappers create excessive ash and can float up the flue while burning, potentially igniting a bird nest blocking the chimney or landing on your roof.
The Danger of Green (Wet) Wood
The most common mistake homeowners make is burning “green” wood—wood that has been freshly cut and hasn’t had time to dry (season).
Fresh wood can contain up to 50% water. When you throw this on a fire, the energy is wasted boiling off the water instead of heating your room. This produces cool, smoldering smoke that condenses inside your flue as creosote.
If you are unsure what creates a clean burn, read our detailed guide on what to burn to clean a chimney (spoiler: it’s dry heat!).
Softwoods: Handle with Caution
Trees like Pine, Fir, and Spruce are softwoods. They are not “toxic,” but they are problematic. They contain high levels of resin (sap).
- Pros: They ignite very quickly and burn hot. Great for kindling.
- Cons: They burn out fast and produce significant soot. Using them as your primary fuel source necessitates more frequent sweeping.
For a sustained, efficient fire, always opt for dense hardwoods like Oak, Maple, or Hickory. Compare the heating values in our wood stove vs fireplace heating analysis.
Consequences of Bad Wood & Maintenance
Burning the items listed above leads to rapid deterioration of your system. The corrosive effects can damage the mortar joints, requiring the best mortar for chimney repair to fix.
If you have burned wet wood recently, you need to assess the damage.
1. Check Your Cap
Soot buildup often starts at the screen of the cap. Ensure you have the best chimney caps for rain installed, and that they aren’t clogged with tar.
2. Schedule a Sweep
How often should you clean a chimney? If you’ve been burning pine or wet wood, you might need it twice a season. You can use the best chimney services, or if you are handy, pick up the best chimney brush for stainless steel liners and do it yourself.
3. Inspect for Leaks
Excessive heat from chemical fires can warp flashing. Check if you need chimney flashing sealant or if you need to waterproof your chimney brickwork.
Essential Tools for Safe Burning
To ensure you are only burning safe, dry wood, these tools available on Amazon are indispensable for any serious homeowner.
1. Digital Wood Moisture Meter
The only way to know if your wood is “Green” or “Seasoned.” Takes the guesswork out of safety.
Check Price on AmazonMove your seasoned wood from the shed to the hearth without the mess. Essential for winter comfort.
View on Amazon →Safe disposal of ash is critical. Never put hot ash in a plastic bag or cardboard box.
View on Amazon →Using the right tools pairs perfectly with the best chimney starters to get your fire going cleanly without needing dangerous accelerants.
Frequently Asked Questions
Can I burn cardboard or pizza boxes?
It is not recommended. Cardboard burns very fast and the ashes are light, often floating up the chimney while still hot. Pizza boxes also contain grease and food residue which create unpleasant odors and attract pests (like raccoons—see how to remove them here).
Is it okay to burn wood with nails in it?
Small nails in pallet wood generally won’t hurt the fire, but they remain in the ash. When you clean it out, they can damage your ash vacuum or injure you. It’s better to avoid them.
Does a gas fireplace need the same care?
Gas units are cleaner but still have requirements. See our guide: Does a gas fireplace need a chimney?
What if I have a chimney fire?
If you suspect a fire (roaring sound, hot walls), evacuate immediately. Read our emergency guide on how to put out a chimney fire for the steps you must take.
For more home improvement tips, check our reviews on the best paint for chimney brick or verify if your insurance covers repairs.