When selecting firewood, it’s important to know which types of wood are safe to burn and which are toxic. Burning certain woods can release harmful toxins and chemicals into the air, posing a risk to your health and indoor air quality. In the UK, there are a few key wood species that should be avoided as firewood.
Hazards of Burning Treated or Painted Wood
One of the most important things to avoid is burning any wood that has been treated with chemicals or painted. This includes:
- Pressure-treated lumber – Used for decks, fencing and outdoor structures. Contains toxic chemicals like arsenic, copper and chromium. Burning releases these toxins.
- Plywood, particleboard and MDF – Contain glues and resins that release formaldehyde, a carcinogen, when burned.
- Painted or stained wood – Burning releases lead, cadmium and other toxins from paints and stains.
These treated and manufactured woods should never be burned indoors or outdoors because of their high toxicity. Burning them produces a range of dangerous fumes and compounds that pose both short-term and long-term health risks.
UK Tree Species to Avoid As Firewood
When it comes to untreated, natural wood, there are also some tree species that are best avoided for burning. These woods release more smoke, creosote and irritating compounds when burned.
All parts of the yew tree, but especially the leaves and seeds, contain the toxic compound taxine. Burning yew wood, trimmings or leaves gives off a poisonous smoke that can be fatal if inhaled. Even burning diseased or dead yew wood is dangerous.
Laburnum is a decorative garden tree, but all parts of it are poisonous. Burning laburnum wood or trimmings releases toxic fumes containing the alkaloids cytisine and anagyrine. These affect the heart and central nervous system.
Rhododendron & Azalea
Rhododendrons and azaleas contain grayanotoxins which can cause vomiting, paralysis and even death if burned. The smoke from burning these ornamental shrubs is highly toxic.
The wood, leaves and seeds of the hemlock tree are very poisonous and contain a neurotoxin called coniine. Burning any part of the hemlock releases this toxin into the air.
Fresh or unseasoned eucalyptus wood releases compounds like cis-ocimene when burned which causes coughing fits if the smoke is inhaled. It also scatters embers and burns erratically.
Sycamore, Ash & Horse Chestnut
These tree woods don’t contain toxins, but they have high sap content. Burning woods with high sap results in a lot of smoke and air pollution. The sap and moisture content also make these woods burn poorly.
Cherry, Walnut & Mahogany
Fresh or unseasoned wood from these tree species gives off unpleasant, acrid smoke when burned. Always allow them 6-12 months to dry out before considering using them for firewood.
Health Dangers from Toxic Firewood
Burning pressure-treated, painted or toxic woods indoors releases large amounts of dangerous chemicals directly into your living space.
Exposure to these wood-burning toxins can cause:
- Headache, dizziness and nausea
- Eye, throat and lung irritation
- Wheezing and breathing difficulties
- Heart palpitations and chest pain
- Muscle weakness and coordination problems
- Vomiting and diarrhoea
Long-term risks include lung damage, kidney and liver problems, neurological effects and cancer. Sensitive individuals like children, pregnant women, the elderly and those with existing health conditions are most at risk from toxic firewood smoke.
Outdoor burning of treated lumber and poisonous woods also pollutes the air around your home. The toxins released can settle on grass and soil and contaminate groundwater if burned repeatedly in the same area.
Safe Firewood Options for Indoor Burning
To avoid breathing in dangerous toxins from firewood, only burn natural, untreated hardwoods that have been properly seasoned. Safe species to burn in the UK include:
- Oak – Slow, steady burn with medium heat and small embers. Needs 12+ months to season.
- Ash – Burns similar to oak with less smoke. Season 6-12 months.
- Birch – Burns hot and fast with good flame. Seasons quickly within 6 months.
- Maple – Very high heat, good coaling and less smoke. Season for 12 months.
- Beech – Low moisture content makes it an ideal firewood. Seasons within 6-10 months.
- Hawthorn – Excellent firewood that’s dense, burns slowly and seasons rapidly.
- Blackthorn – Similar burning qualities to hawthorn.
- Holly – Hard, dense wood that burns very hot. Needs 12+ months to dry out.
- Apple, pear, cherry, plum – Orchard wood burns hot and fast with less smoke. Dry 6-12 months.
- Douglas fir – Softwood that burns brightly and evenly with resinous scent. Dry for 6+ months.
Look for downed branches or buy split firewood labelled as seasoned, kiln-dried or ready to burn to ensure it has dried adequately before burning. Store your firewood in a dry shelter for optimal seasons before use.
Softwoods like pine and spruce are also safe to burn as firewood. However, they generate more creosote so need proper stove maintenance and cleaning.
Firewood Storage Safety Tips
- Stack firewood outdoors on pallets or blocking to keep it raised off the ground and promote air circulation.
- Cover the top of the stack with a tarp or breathable firewood bag, but leave the sides uncovered for airflow.
- Store different types of wood separately to prevent cross-contamination.
- Check periodically for insect pests like termites or beetles. Discard any infested wood.
- Allow each type of wood to season fully before burning to reduce moisture, smoke and burn efficiently.
- Never store firewood indoors or bring it inside until you are ready to burn it.
Summary of Wood Burning Safety
- Avoid burning pressure-treated lumber, plywood, MDF, painted woods or wood debris as they contain toxins.
- Do not burn yew, laburnum, rhododendron, azalea, hemlock, eucalyptus or unseasoned woods with high moisture content.
- Only burn dry, seasoned hardwoods like oak, birch, ash and beech that have aged for 6-12 months.
- Season and dry all firewood fully before burning to reduce smoke and burn cleanly and safely.
Choosing the right woods to burn in your indoor or outdoor fireplace or stove will ensure good air quality and prevent dangerous toxins being released into your home and outdoor spaces. Stick to dry, untreated dense hardwoods and refrain from using painted, pressure-treated or poisonous woods as fuel. With proper firewood selection and storage, you can avoid exposure to toxic smoke and enjoy safe, warm fires.