When it comes to enjoying a fire in your home or outside pit, not all wood is created equal. Sure, they all produce ash and smoke but some also release dangerous toxins that are easily inhaled.
I’ve burned my fair share of scrap lumber from building projects. At one point, I had a pile of old treated lumber and I was not sure what to do with it. Do I take it to a landfill? Is it safe to burn?
If you ever find yourself in a similar situation or are tempted to burn pressure treated wood, keep the following in mind.
Never burn pressure treated lumber in outside fire pits and especially, not indoors. Doing so releases harmful levels of chemicals like arsenic and chromium in the ash and smoke. Not only is it harmful to the health of people nearby, it is also illegal in some areas.
While throwing the occasional chunk of pressure treated wood in the fire may seem innocent enough, don’t do it! Keep reading and you’ll learn why it isn’t safe.
What is pressure treated wood
Most types of untreated wood quickly succumb to insects and decay. Back in the 1930s someone came up with the brilliant idea to pressure inject lumber with pesticides and preservatives that drastically increases the life of wood in harsh environments.
The process for pressure treating lumber is fairly straight forward.
- First, the kiln dried lumber is sorted and incised on rollers. The incising creates the characteristic holes in treated lumber and improves the penetration of the preservative.
- Next, the lumber is slid into a giant steal vacuum tube and the pressure is raised to 160 psi. At the right pressure, the chemicals are injected into the tube and the preservative presses into the cell structure of the wood.
- Finally, the wood is removed from the tube and allowed to drip dry for 2 to 10 days before being shipped to a lumber yard.
While treated lumber is a good thing for building long lasting structures, it is pretty bad for anyone who comes into contact with it.
Prior to 2002, pressure treated lumber was made using chromated copper arsenate (CCA). This cocktail of copper, chromium and arsenic has anti-fungal and pesticide qualities that keep decay at bay. But it also causes enough health problems that the Environmental Protection Agency (EPA) decided to ban its use in residential construction.
Today’s treated lumber contains a safer compound called alkaline copper quat or ACQ for short. It protects against decay and rot just like CCA but leaves out the arsenic and chromium. The EPA says this product is much safer for people and the environment.
Although, that doesn’t mean you can burn it. The copper in the treated wood still releases a host of toxins when burned. It may not leech into the soil or poison you through your skin but the dust from cutting or ash from burning is still a concern.
How to tell if lumber is pressure treated
Spotting pressure treated wood is easy. The first clue are incision marks that uniformly cover the wood.
Now, not all treated lumber has the incisions so the next thing to look for is color. Most treated wood has a greenish-brown tint. And if you cut the board you’ll also see that the preservative has formed a brown colored ring as it seeps towards the center of the board.
Pressure treated lumber also has a different smell than raw, untreated lumber. You can likely recognize the characteristic smell of pine and fir. Most treated lumber has minimal wood scent and instead smells like chemicals.
Can you burn old pressure treated wood
It’s reasonable to think that old treated lumber is okay to burn. I know I did. After all, treated wood that’s 20 years or older no longer smells like chemicals and most of the coloring has faded. Surely it’s safe to burn now right?
The only problem is the toxins still remain. Arsenic, copper and chromium don’t disappear with time. Therefore, it is not safe to burn old pressure treated wood either.
As I said before, even the newer treated wood that uses safer compounds to preserve it are still too dangerous to risk burning.
There just isn’t any way around it. Burning pressure treated lumber is a no-go.
What makes burning treated wood unsafe
So you get the point, burning treated wood releases harmful toxins. But I’m not standing in the smoke or eating a handful of ash. What’s the big deal?
It’s definitely obvious to most of us that burning treated wood in your home is not smart. Any sort of air flow imbalance can pump smoke and ash into areas you live and eat.
There was one such case reported by the Journal of American Medical Association of a family that burned treated lumber in their home for winter heat. After weeks and months of exposure, the family suffered severe health affects. Their hair fell out, they suffered from nosebleeds and headaches and two children experience serious seizures. Some health problems never went away.
Even in outdoor fire pits, all it takes is the inhalation of small amounts of toxins over time to create chronic health issues. You may not be standing around the fire when the treated wood burns but the ash settles around your yard and gets kicked up later for you to inhale.
The biggest danger of burning treated wood is that it only takes a little bit of exposure to harm you.
Other types of wood you should not burn
Pressure treated wood isn’t the only wood product you should not burn. Here is a quick run down of what needs to stay out of your fireplace and head to the landfill instead.
- Stained wood: Most stains and varnishes contain compounds know to be toxic and carcinogenic. Some argue that boards coated with natural oils are safe but I wouldn’t risk it.
- Painted wood: Most modern paints are relatively harmless when dry but once burned, chemical reactions from the heat can create toxic fumes. Especially, old painted wood. It likely contains lead and creates contaminated ash.
- Plywood, particle board and chip board: To be honest, this one took me by surprise at first. I know I’m guilty of this but after learning about all the harsh chemicals and glues required to make products like plywood, I now see how dangerous it is to burn.
- Creosote coated wood: Old rail road ties used in landscaping and chucks of telephone poles are coated in creosote. This tar-like coating is a probable carcinogen and should never be burned.
- Driftwood: I love a good beach-side fire and driftwood seems like an ideal fuel. The only problem is that the wood soaks up metal salts as it floats in the ocean and burning releases them in harmful fumes. These same metal salts create striking lavender-blue flames. It may be enchanting to look at but it’s still toxic.
- Pallets: It seems like everyone has a pallet or two laying around. Whether it’s for a craft project or storage, think twice before tossing it in the fire. Many pallets contain a methyl bromide pesticide to keep wood beetles at bay. They usually have an “MB” stamped on them. However, it’s better to be safe and avoid burning pallets all together.
There is a laundry list of things you should not burn and I could write a novel about it. Just remember to use common sense and most often you’ll be okay. As a rule of thumb, if it is manufactured or manmade, don’t burn it inside or outdoors.
How to dispose of pressure treated lumber
You more than likely found this article because burning up scrap lumber is a cheap and easy way to dispose of unwanted wood. But it’s not a good option. So then what is the best way to get rid of pressure treated wood or other wood not suited for burning?
The best way to get rid of treated wood is to reuse it. Salvaging wood for other projects is a great way to avoid wasting resources. You’d be surprised how useful scrap wood is to have around.
Don’t have any future building projects to recycle treated wood? Try selling it. Treated lumber is expensive and loads of people would love to use reclaimed wood for non cosmetic applications. Someone making yard borders or planter beds would love to get their hands on affordable material. Plus, you’ll get cash in your hand.
A less than ideal way to dispose of treated wood is at your local landfill or refuse center. Sometimes this is your only option for lumber that can’t be reused. Be sure to ask a solid waste employee if there is a specific spot where treated wood should be dumped.
Taking wood to the dump may seem like a waste but it is definitely safer than burning it.
Conclusion
It’s so easy to think that any wood product can be burned in a fire. After all, what’s one little piece of treated wood going to harm. Unfortunately, the few BTUs you get out of it aren’t worth the health risks.
Take the time to find clean, dry and locally sourced wood. I have an entire article dedicated to finding other free sources of firewood so you don’t need to rely on burning treated lumber. Check it out. Your neighbors will thank you, the environment won’t suffer and you’ll live a longer, healthier life. Burn clean and enjoy the fire!
