Can You Burn Cardboard or Paper in a Fireplace?

How paper and cardboard burn compared with logs

A log burns from the outside in. Heat works slowly into the wood, gases escape and burn, and the fire settles into a steady rate. Paper and cardboard are thin, dry and full of trapped air, so the whole mass catches at once. The fire jumps to several times its size within seconds, then collapses just as quickly.

In between, the fireplace behaves like a bellows. The surge of hot gas up the flue pulls a strong rush of air through the opening, and light, half-burned pieces ride that current upward. Corrugated cardboard is the worst for this, because its layers peel apart into wide, flat flakes that stay aloft while they glow.

Embers on the roofline

Most of those flakes burn out inside the chimney. Some do not, and they leave the top still glowing. In a detached house with a tall chimney, they usually land on a roof or lawn and go out. In a block of attached rowhouses or brownstones, the picture changes: neighbors' roofs sit a few feet from your chimney top, rooftop decks and planters are common, and gutters fill with dry leaves every fall.

Flat roofs with older roll roofing or tar patches, common on rowhouse blocks from Brooklyn to Jersey City to South Philadelphia, are not where you want a glowing piece of cardboard to come to rest on a dry, windy night.

A chimney cap with a mesh screen catches the larger embers, which is one reason caps are worth having on every wood-burning flue. Mesh does not stop the finest sparks, and it can clog with soot and creosote over a season, which chokes the draft. A cap helps; it does not make paper fires safe.

Creosote and a sudden burst of heat

Most wood-burning flues carry some creosote, even well-kept ones. During a normal fire it stays put, because the flue walls warm gradually and the deposit stays well below the temperature it needs to ignite. A box of cardboard or an armful of paper changes that. The flash of heat hits the lower flue all at once, and if the creosote there is thick or glazed, it can catch.

Once lit, that kind of fire can roar like a train, throw sparks and flames from the top, and crack clay flue tiles in minutes, even if it burns itself out. The holidays are the classic setup: boxes, wrapping paper and tissue piled by the tree, a fire already going, and the fireplace looking like the easy place to clear the floor.

Why the condition of the flue changes the risk

The same armful of paper is a bigger gamble in some chimneys than others. A flue with thick or glazed creosote gives the flash of heat something to ignite. An unlined flue, still common in older rowhouses and brownstones, or one with cracked clay tiles, lets heat reach the brick and, in places, the wood framing beside the chimney. A chimney that shares a party wall with a neighbor's flue can pass heat and smoke through open mortar joints into the house next door.

None of those conditions is visible from the living room. If you do not know when the chimney was last inspected, or the flue has never been looked at since you bought the house, assume it is not ready for a test of heat and keep fires small and steady until it has been checked.

Coatings, inks and holiday wrap

The EPA's list of what not to burn includes household trash, cardboard, plastics, foam, and the colored ink on magazines, boxes and wrappers. Wrapping paper is often coated, printed with heavy inks, or laminated with foil or a thin plastic film. Glossy catalogs and magazines are clay-coated. None of that burns cleanly, and the smoke and fine ash carry the coatings with them, some into the room, some into the neighbors' air.

Ribbon, gift bags, tissue with glitter and the plastic windows in envelopes are worse still. Put all of it in recycling or trash under your town's rules.

Closed wood stoves and inserts are no place for trash either. The EPA's list notes that these materials may damage the appliance itself, and stove manuals commonly warn that colored paper, glossy print and plastics can foul a catalytic combustor or the baffle above the fire.

Kitchen paper and other things that end up in the firebox

A few items show up in fireplaces again and again after a busy weekend. Each has its own problem:

Cardboard leaves its own mess too. Tape, staples and plastic labels end up melted on the grate or mixed into the ash, and the light, papery ash floats into the room the next time the screen or doors are opened.

• Pizza boxes: cardboard plus grease, which flares and leaves a smoky residue
• Paper plates and cups: often coated with plastic or wax to hold liquid
• Egg cartons and shipping fill: fast, hot and full of trapped air
• Shredded paper: packs down, smothers the fire, then flares when it catches
• Takeout containers and food wrappers: coatings, plastic and food residue
• Junk mail by the bundle: glossy inserts and plastic windows mixed in

Starting a fire without a pile of paper

The EPA's guidance on lighting a fire names newspaper, dry kindling and all-natural fire starters, and it says not to start a fire with gasoline, kerosene or charcoal starter. Those liquids vaporize and ignite explosively in a confined firebox, and they have no place in an indoor fireplace.

A good start needs less paper than most people use. Two or three sheets of plain newsprint, twisted loosely, under a layer of dry kindling no thicker than your thumb, with two small split pieces of firewood on top, will catch reliably if the damper is open and the wood is dry. Some people prefer a top-down build, with the larger pieces at the bottom and kindling and paper on top, which burns down slowly and smokes less at the start. If the fire needs repeated handfuls of paper to keep going, the wood is too wet or too big, or the flue is not drawing.

If a lot of paper already went in

Watch and listen for signs that something more than the paper caught: a deep roar from the chimney, popping or cracking inside the flue, thick smoke from the top, or sparks and flames above the chimney. If you notice any of that, leave the house with everyone in it and phone 911 from the sidewalk or yard. Do not throw water into the firebox or up the flue.

Even when nothing dramatic happened, a big paper fire can crack tiles or shake loose deposits. Black, puffy flakes or bits of tile in the firebox the next morning, or a fireplace that suddenly draws poorly, are reasons to have the chimney inspected before the next fire. Under NFPA 211, anything that may have damaged a chimney is a reason to have it inspected, and a runaway paper fire qualifies.