The answer to whether you should burn pressure-treated wood is unequivocally no. This lumber is chemically preserved to withstand decay, insects, and moisture, making it unsuitable for combustion in any setting, including fire pits, fireplaces, or wood stoves. Burning pressure-treated (PT) wood releases chemical preservatives into the air and concentrates them in the ash. These toxic compounds are not destroyed by the heat and create a significant hazard to human health and the environment.
Why Burning Pressure Treated Wood is Dangerous
Pressure-treated wood is lumber that has undergone a process to force chemical preservatives deep into the wood fibers. This treatment extends the lifespan of the wood, making it a popular choice for outdoor applications like decks, fences, and playground equipment. The wood is placed inside a large cylinder, where a liquid preservative solution is pumped in under high pressure, ensuring deep penetration.
The specific chemicals used are biocides designed to prevent fungal decay and insect infestation. Historically, the most common preservative was Chromated Copper Arsenate (CCA), which contained copper, chromium, and inorganic arsenic. Although residential use of CCA was phased out in the early 2000s, older structures and salvaged wood may still contain it.
Modern residential PT wood typically uses copper-based compounds like Alkaline Copper Quat (ACQ) or Copper Azole (CA). These newer formulations still contain high concentrations of heavy metals. When the wood is burned, the heat breaks the chemical bond holding these preservatives, releasing them as toxic gases and fine particulate matter.
Health and Environmental Risks of the Smoke and Ash
The smoke produced from burning pressure-treated wood contains airborne toxins, including heavy metals like arsenic and chromium. Inhaling this smoke, even briefly, can cause immediate symptoms such as respiratory irritation, nausea, and headaches. The fine particulate matter carries these toxic compounds deep into the lungs, posing a risk to the nervous system and increasing the potential for long-term health problems.
Exposure is not limited to the immediate vicinity of the fire, as the smoke can travel long distances, affecting neighbors, pets, and wildlife. Cooking food over a fire made with PT wood is hazardous, as the toxins can settle onto the food and be ingested. The danger is particularly acute for children and individuals with pre-existing respiratory conditions.
The ash remaining after the wood has burned is the most concentrated source of contamination. The combustion process does not destroy the heavy metals; instead, it concentrates them into a toxic residue. Studies have shown that even a small amount of ash from CCA-treated wood can contain lethal doses of arsenic.
This toxic ash poses a severe environmental risk if spread on the ground, used in gardens, or disposed of improperly. The concentrated chemicals can leach into the soil and groundwater, causing irreversible contamination. Once the soil is contaminated, it can harm plants, enter the food chain, and pose a long-term threat to the local ecosystem.
Safe and Legal Disposal Alternatives
Because of its inherent toxicity, pressure-treated wood is often classified as a special waste material, and open burning is prohibited by law in many jurisdictions. Proper disposal requires careful attention to local municipal waste regulations. These rules prevent the release of heavy metals into the environment and protect public health.
For small quantities of PT wood, some local solid waste facilities may allow disposal with regular household trash, but this is not universally permitted. For larger amounts, such as from a deck demolition, the wood must be taken to a licensed construction and demolition (C&D) landfill. These facilities are designed and permitted to handle materials containing chemical preservatives.
It is advisable to contact your local waste management authority or public works department before attempting disposal. They can provide current information on approved C&D landfills or specialized hazardous waste collection events. While recycling options for PT wood are limited due to the chemical content, proper disposal at a designated facility ensures the material is contained safely and legally.