A roaring fire is one of the best parts of winter. It adds warmth, charm, and a sense of comfort to any room. But before you toss something into the flames, take a second to think. Burning the wrong materials can release toxic chemicals, damage your fireplace, and even start a dangerous house fire. Here are 17 things you should never burn in your fireplace—and why keeping them out matters more than you think.
Painted or Treated Wood
Old furniture, fencing, and building scraps may look like good firewood, but don’t be fooled. If the wood is painted or treated, it contains chemicals that release harmful fumes when burned. Paint can include lead or heavy metals, especially in older pieces. Treated lumber often contains pesticides or preservatives like arsenic. Burning this wood in a closed space like your home can release those toxins into the air, where you and your family breathe them in. It also produces thick, corrosive smoke that can stick to the inside of your chimney.
Pressure-Treated Lumber
Pressure-treated wood is built to last outdoors. It’s commonly used in decks, fences, and landscaping. But the chemicals that make it durable—like copper, chromium, and arsenic—become dangerous when burned. The smoke from treated wood carries toxic compounds that are harmful to your lungs, eyes, and skin. Even short-term exposure can cause breathing problems or chemical irritation. It’s also bad for the environment, as those fumes escape through your chimney and pollute the air around your home.
Plywood and Particleboard
Plywood, MDF, and particleboard are engineered wood products made with glue and resin. These materials may hold together furniture and cabinets, but they break down into toxic fumes in a fire. When burned, the adhesives release formaldehyde and other harmful gases. The smoke can fill your home with unpleasant, dangerous air, and the residue left in your chimney can build up fast. If you want a clean fire and safe air, stick to natural, untreated hardwoods.
Christmas Trees
It’s tempting to toss a dry Christmas tree into the fireplace after the holidays. After all, it’s just wood, right? Not exactly. Christmas trees contain sap, which burns quickly and unpredictably. The needles are dry and highly flammable, producing fast-burning, high-temperature fires. This can send flames shooting up your chimney and ignite creosote buildup—causing a chimney fire. The smoke is also dense and irritating, making it hard to breathe. Take your tree to a recycling center instead.
Cardboard Boxes
Cardboard burns fast, and that speed can be dangerous. Flames from cardboard can rise quickly and unpredictably, especially in enclosed fireplaces. On top of that, most cardboard is printed with colored inks and treated with chemicals. Burning it releases toxic fumes and particulates that you don’t want in your lungs—or in your home. Floating bits of cardboard ash can also fly up your chimney and land on your roof, increasing fire risk. Recycle your boxes instead of burning them.
Magazines and Glossy Paper
That shiny magazine paper may look like regular paper, but it’s full of trouble. Glossy pages are coated with chemicals to keep them smooth and colorful. When you burn them, you release those coatings into the air in the form of smoke and ash. Many inks also contain heavy metals, which become airborne pollutants. Burning a few pages may not seem like much, but the chemical buildup can quickly affect air quality inside your house.
Wet or Green Wood
Freshly cut wood may smell earthy and natural, but it’s full of moisture. This water content leads to smoldering fires, excess smoke, and creosote buildup in your chimney. Wet wood also gives off very little heat, making it a poor source of warmth. Fires with green wood tend to sputter, hiss, and send smoke pouring into your room. Always use dry, seasoned hardwood that’s been air-dried for at least 6–12 months to get the cleanest, most efficient burn.
Read More: 13 Items That Are a Fire Hazard If You Don’t Clean Them Enough
Dryer Lint
Dryer lint seems like a clever firestarter—light, fluffy, and flammable. But it’s a mix of cotton, polyester, and synthetic fibers. When burned, it melts and gives off toxic fumes from plastics and chemical residues. Dryer lint can also burn erratically, sending sparks into the room or up the chimney. If you’re looking for kindling, opt for natural materials like dry twigs or wood shavings. Save the lint for compost—or the trash.
Plastic
Plastic of any kind should never go into a fire. Whether it’s a bottle cap, food wrapper, or old toy, burning plastic releases dangerous toxins like dioxins and furans. These chemicals are linked to cancer, hormone disruption, and other health problems. The smoke from plastic also smells awful and can irritate your lungs, eyes, and throat. Even small pieces can coat your chimney with sticky residue. Keep plastic out of your fireplace at all costs.
Painted Driftwood
Driftwood may look pretty stacked by the fire, but it’s a poor choice for burning. Not only is it often coated with old paint, but it also absorbs salt from the sea. When salt burns, it releases chlorine gas, which is highly toxic. The chemical reaction can damage your chimney lining and corrode metal parts. Plus, the smoke from salt-heavy wood is thick and harsh. Driftwood is better used as decoration, not fuel.
Paper with Colored Print or Wrapping Paper
Gift wrap, especially the shiny kind, is covered in dyes, foils, and even plastic. When it burns, it doesn’t just disappear—it releases toxic fumes and leaves behind ash filled with synthetic chemicals. Some paper may also ignite too quickly, creating sudden flare-ups or floating embers. That’s not just bad for your indoor air; it also raises the risk of chimney fires. Dispose of wrapping paper properly—don’t let it become kindling.
Fire Accelerants
Using gasoline, lighter fluid, or kerosene to start a fire might seem like a quick fix, but it’s a major hazard. These substances ignite explosively and can send flames shooting out of the fireplace. They also produce intense heat that your chimney may not be built to handle. Plus, the fumes from accelerants are poisonous and linger in the air. A fire should be gradual and controlled—not a mini explosion. Use kindling and patience instead.
Rubber or Foam
Burning rubber, like from old shoes or tires, releases thick black smoke and an overwhelming smell. Foam—like that found in cushions or mattress pads—is just as bad. Both materials melt as they burn, releasing noxious fumes and sticky residue. These fires burn hot and can damage your chimney lining. The chemical output is dangerous to breathe and lingers long after the flames die out. These materials belong in a disposal center, not your fireplace.
Leaves and Pine Needles
Yard waste burns fast, which means you get lots of flames but very little heat. Pine needles and dry leaves are especially risky because they contain oils that flare up quickly. Burning them in a fireplace can send embers flying into the air or up your chimney, increasing fire risk. The smoke is also thick and full of irritating particles. Use these in compost or yard waste bins—not your fireplace.
Coal
Coal produces a long, hot burn, but it also gives off large amounts of carbon monoxide. Unless your fireplace is specifically rated for coal use, don’t attempt to burn it. The intense heat can damage your chimney, and the buildup of gases can create deadly indoor air conditions. Coal also produces more ash and soot than wood, making cleanup harder and more dangerous.
Cat Litter or Pet Waste
Yes, some people really try this. Burning used litter or pet waste is not only gross—it’s hazardous. Litter can contain clay or silica, which release harmful dust and fumes when heated. Pet waste, meanwhile, is full of bacteria and ammonia that becomes airborne when burned. These materials don’t belong in the fireplace, the backyard fire pit, or anywhere near open flames. Keep it simple: bag it and trash it.
Trash or Household Garbage
General household waste is a mix of plastic, foil, food wrappers, synthetic materials, and unknown chemicals. When burned, these items release a cocktail of toxins into your home and the environment. The resulting smoke can be harmful to people, pets, and even your chimney. Don’t treat your fireplace like an incinerator. Stick to clean, seasoned firewood and keep the garbage where it belongs.
Final Thoughts
A fireplace is meant for comfort, not convenience. Tossing random items into the flames can turn a cozy evening into a health hazard—or a full-blown emergency. Use only dry, seasoned hardwood, and never burn materials that release toxic fumes, burn unpredictably, or damage your chimney. When in doubt, keep it out of the fire. Your lungs, your home, and your fireplace will thank you.
Read More: What Not to Burn in Your Backyard Fire Pit