Never burn treated wood used for wood fences or pressure treated, chemically treated or painted wood indoors or outdoors. The chemicals in these types of finished wood may give off dangerous toxins that you don’t want to breathe in and burning wood outdoors is often illegal in many areas.
Let’s take a closer look at why you shouldn’t burn wood fence panels and what you can do instead.
What type of wood is used to build fences?
Commonly used woods used to build fences include pine, cedar, cypress and redwood. Wood used to build fences are usually pressure treated fence panels that help the wood withstand elements year round.
Pressure treating involves blasting the wood with chemicals in a pressurized container to strengthen the wood and make it more impervious to rot, insects, mold, water, ice and other damaging factors.
While residential wood fences are typically made from long rectangular panels with square edges, you might also have a fence made from closely aligned Stockade fence panels which have pointed edges at the top.
Because the wood is treated with dangerous chemicals, burning the wood can lead to the release of these chemicals in the air and into the air you breathe, which is why it isn’t recommended.
What chemicals are used to build fence wood?
Pressure-treated wood was traditionally coated with a combination of copper, chromium and arsenic. Painted woods may have been painted with outdoor use lead-based paints stains that are usually formulated in a way to offer protection against the elements, too.
The chemicals that are used to build fence wood have traditionally included the following:
Copper – Copper is a fungicide which helps to prevent the growth of parasites like mildew, black spots, rust and others that cause unsightly damage on wood. High levels of copper are considered dangerous to humans and burning wood that contains copper can result in particles being inhaled, leading to nose and throat irritation.
Chromium – Chromium is not necessarily harmful in this form as long as it isn’t inhaled which again speaks to why we shouldn’t burn wood that has been pressure-treated.
Arsenic – Arsenic is a dangerous chemical compound used for many decades in the manufacture of pressure-treated wood. It is no longer used due to health concerns it creates for humans and also the environment when it inevitably leeches into the ground. It is no longer used in pressure-treated wood for that reason which we’ll elaborate on below. But many older fences can have arsenic in it if they were built before January 2004 which is when chromated copper arsenate (CCA) pressure treated wood ceased to be made.
Paint – Depending on the age of the paint, it may contain lead if it’s old enough which is very dangerous to burn due to the toxins that will be released. Even newer paints have other chemicals that will be released when burned which is why this should also be avoided. And it’s possible that the wood may have been painted even if was pressure treated, perhaps by a previous owner.
Wood finish – Wood finishes were traditionally petroleum-based and thus very toxic due to their design. They are also highly flammable too. Typically many toxins are released during the drying or curing process. But older wood finishes were very high in Volatile Organic Compounds (VOCs) many of which are now either banned or significantly reduced in manufactured finishes. Avoid burning wood that has been finished due to the potential of toxins that can be released.
How to read the labels on pressure treated wood
The dangers of the older style CCA wood is specifically related to the arsenic content. It’s dangerous to humans and particularly children but is also dangerous to the ground around you. If you have a fruit or vegetable garden in your background that is surrounded by a wooden fence built with CCA-treated lumber, over time it can and will contaminate the soil and ground.
Here’s what to look for when reading the labels on pressure treated wood.
L-P22 – This stamp indicates that the pressure treated wood has arsenic and is designed for direct contact with the ground. In other words as the wood ages, the chemicals contained in the wood can leech into the ground and contaminate it.
Borate – If you see the words Borate, Tim-Bor, Hi-Bor or similar wording on the wood, this means the wood is of the borate variety. It’s a newer version of pressure treated lumber that looks exactly the same but contains the natural mineral borate which gives the wood protective properties that chemicals like the aforementioned copper, chromium and arsenic used to provide.
ACQ – ACQ stands for Alkaline Copper Quaternary which is a newer treatment being used to replace CCA. ACQ does tend to leech more toxins into the ground than CCA-treated lumber but the toxins themselves are considered to have lower toxicity than those found in copper, chromium and arsenic.
What safer versions of pressure treated lumber are now available?
Rather then choosing an older style type of pressure treated lumber with chemicals that can leech into the ground and make it more difficult when it comes to discarding it, you can choose a new form of the wood that doesn’t contain as many toxins.
Environmentally friendlier pressure treated woods now exist that avoid use of chemicals such as copper, chromium and arsenic. Instead, they use sodium silicate and a melted mix of sand and soda ash.
The aforementioned Alkaline Copper Quaternary (ACQ) treated woods are also an option. While not completely toxin-free, they tend to have less toxins that older style copper chromium arsenic-treated woods from the past.
By design, newer forms of pressure treated lumber are less chemical-laden than in the past but it still helps to learn about available options and to familiarize yourself with what ingredients are used in their place.
How should you safely discard wood fencing?
Think of ways you might repurpose your wood for your own needs around the house. If you’re handy, old wood fencing can be used to build furniture, wine racks, outdoor garden boxes and other useful items that you can actually use.
Short of that, you can check with your local recycling and waste companies as many pick up wood materials or offer drop off areas where you can leave the discarded wood.
You might also consider placing an ad online as people will often agree to pick up old unwanted wood for their own purposes at no cost to you.
How to tell if wood is safe to burn
When considering if you can burn wood, there are a number of things to consider including of course when it has been treated with toxic chemicals you don’t want to burn.
To summarize, avoid burning wood that has the following characteristics.
Don’t burn wood that:
- Has been pressure treated, painted, stained or otherwise covered with any chemical. Pressure treated fence panels shouldn’t be burned.
- Is still green and thus hasn’t had a chance to properly dry out and age. Damp wood won’t burn well and tends to smoke when wet.
- Has the word “poison” in it (i.e poison ivy) as they typically have irritants that you may inhale which is unhealthy.
- Isn’t local. When you don’t know the source of the wood, you don’t know what it might contain that could be dangerous (i.e. it has termites, disease, etc).
- Has cones or sap as they both crackle and pop.
- Was discarded or found on the ground i.e. driftwood.
- Is soft. Softwood like pine and fir should be avoided since they tend to burn quickly and cause more smoke than hardwoods which are more appropriate for burning.
- Was previously used for cheap furniture i.e. plywood, particle board, chipboard. They tend to have glue or other chemicals that when burned, give off toxins.
Given that the wood has been treated with chemicals, you also run the risk of a fire burning out of control and spreading which can be a major risk.
In some areas, burning wood outside is illegal so you may face the possibility of being fined if caught so letting it rot might be the better option if possible.