Wood Burning and UK Air Quality: What DEFRA's Numbers Actually Show

If you are choosing between a wood-fired and a gas sauna heater, the environmental question is usually framed as a simple one: wood is renewable, gas is a fossil fuel, so wood must be the greener choice.

The official numbers make it more interesting than that. On air quality — the particulates you and your neighbours actually breathe — wood loses badly. On carbon, wood wins, though for a reason worth understanding rather than just quoting.

Here is what the government data actually shows, and what it means for a sauna at the bottom of a British garden.

Domestic burning is a fifth of UK fine-particle pollution

DEFRA's national emissions statistics for the 2024 data year put domestic combustion at 20% of total UK PM2.5 emissions and 11% of PM10.

Two details matter before that number gets misused in either direction.

First, "domestic combustion" is not only wood. DEFRA's category covers households burning wood, solid smokeless fuels, coal, and fuels derived from waste such as coffee logs. Wood is a large part of it, not all of it. Anyone quoting the whole 20% as "wood burning" is overstating the case.

Second, the figure has moved a great deal, and you will still find older numbers circulating. A widely-reported 38% figure was revised down to roughly 17% in 2022 when DEFRA replaced a survey of around 1,000 households with a far larger 10,000-household study — and that older figure also covered a wider set of sources than regulated stoves. So if you see 38%, it is out of date. The current published figure is 20%.

For scale: total UK PM2.5 emissions were 53 thousand tonnes in 2024, down 75% since 1990 and down 4% on 2023. Domestic burning is one of the few sources that has not fallen at anything like that rate, which is precisely why it now accounts for such a large share of a much smaller total.

Why PM2.5 specifically

PM2.5 means particles under 2.5 micrometres. They are small enough to travel deep into the lungs and, in part, into the bloodstream — which is why they are associated with asthma, cardiovascular disease and lung cancer, with emerging evidence linking them to dementia, low birth weight and Type 2 diabetes.

The World Health Organization's 2021 guidelines set the annual mean at 5 µg/m³, halved from the 2005 figure of 10, and state that no safe threshold has been identified. UK expert advice through COMEAP takes the same position: PM2.5 is treated as a pollutant with no known safe level, so reductions produce health benefits at any starting concentration.

That framing matters for a garden sauna. There is no exposure level at which the smoke stops counting — which is a different question from whether it is legal, and a different question again from whether your neighbours will mind.

How much cleaner is gas, really?

You will see a precise-sounding claim that LPG produces "100 to 200 times fewer particulates" than wood. We cannot substantiate that ratio and we are not going to repeat it. The underlying emission factors for LPG particulates are derived from natural gas data and are rated poor quality by the US EPA, so any exact multiple built on them is false precision.

What is properly sourced:

• EU Ecodesign rules permit up to 375 g of PM2.5 per gigajoule for wood stoves. That is the ceiling for a new, compliant stove — not a worst case.
• The UK Chief Medical Officer's 2022 annual report states that even Ecodesign stoves are "several hundred times more polluting than gas central heating."

So: gas is dramatically cleaner on particulates, by a margin best described as hundreds of times rather than a specific figure. A propane sauna heater produces no visible smoke and negligible particulate matter. That is the honest version of the claim, and it is still a decisive one.

The carbon side — where wood wins, and why

We would rather explain this than skip it.

On official UK reporting factors, wood scores very low on carbon: wood pellets carry roughly 0.012 kgCO₂e/kWh in Scope 1, against LPG at about 1.56 kgCO₂e per litre. On paper, wood is barely emitting anything.

The reason is an accounting convention. Burning wood does release CO₂ — around 1,436 kgCO₂e per tonne of it — but under the GHG Protocol that combustion CO₂ is classed as biogenic and reported outside the scopes, on the basis that the carbon was absorbed by the tree as it grew and will be reabsorbed by replacement growth. It is not that wood emits less carbon at the point of burning. It is that the carbon is counted elsewhere.

Whether that convention reflects reality depends on things a sauna owner cannot see: whether the wood is genuinely from sustainably replanted sources, and how long regrowth takes. Taken at face value on official figures, though, wood is the lower-carbon fuel, and we are not going to pretend otherwise to sell a gas heater.

The honest summary: the environmental case for gas rests on air quality and on your neighbours, not on climate.

The legal bit: smoke control areas

This is the part most sauna retailers do not mention, and it is the one that can actually stop your project.

Large parts of urban Britain are smoke control areas. Inside one, you may only burn authorised fuel unless your appliance is on DEFRA's exempt appliance register. The government's guidance is explicit that this applies to a building such as a summerhouse with a chimney on its roof — which describes a garden sauna precisely.

So inside a smoke control area, a wood-fired sauna stove must be DEFRA-exempt. Many sauna stoves are not. And note that Ecodesign-ready is not the same as DEFRA-exempt — Ecodesign has applied to new stoves since January 2022, but a smoke control area needs the exemption specifically.

Penalties in England run to £300 for emitting smoke from a chimney and up to £1,000 for buying unauthorised fuel.

Check your postcode with your local council before ordering a wood-fired sauna. If you are in a smoke control area and the stove you want is not on the exempt register, your realistic options are an exempt stove, an electric heater, or gas.

What this means for choosing a sauna heater

	Wood-fired	Gas (LPG)	Electric
Particulates	High — the main issue	Negligible	None at point of use
Carbon (official factors)	Lowest	Higher	Depends on grid mix
Smoke control areas	Needs an exempt appliance	Unrestricted	Unrestricted
Visible smoke	Yes	None	None
Needs mains power	No	No	Yes

Our own position, stated plainly: if you love tending a fire, you are not in a smoke control area, and your nearest neighbour is not downwind of the flue, a wood-fired sauna is a genuine pleasure and the lower-carbon choice. We sell them and we will keep selling them.

If you are in a terrace, a suburb, or anywhere the smoke has somewhere to go that is not your own garden, gas gives you off-grid heat without the particulates or the neighbour problem — and without a trench and an electrician's quote.

Common questions

Is a wood-fired sauna bad for air quality?

It contributes to the problem. Domestic combustion accounted for 20% of UK PM2.5 emissions in 2024, and even Ecodesign-compliant stoves are described by the UK Chief Medical Officer as several hundred times more polluting than gas heating. A sauna burns far less wood over a year than a home heated by a stove, but the emissions per hour of burning are of the same character.

Can I have a wood-fired sauna in a smoke control area?

Only with a DEFRA-exempt appliance, or by burning authorised smokeless fuel. Government guidance applies this specifically to garden buildings with a chimney. Ecodesign-ready is not sufficient — check the DEFRA exempt appliance register for the exact stove model.

Is gas or wood better for the environment?

It depends which environmental problem you mean. Gas is far better for local air quality and produces no visible smoke. Wood is lower-carbon on official UK reporting factors, because its combustion CO₂ is treated as biogenic and reported outside the scopes. The case for gas is about particulates and neighbours; the case for wood is about carbon.

Do gas sauna heaters produce particulates?

Negligibly. Propane burns cleanly with no visible smoke and no ash. Combustion still needs proper flueing and ventilation, which is why gas heaters are commissioned rather than simply plugged in.

What about the smell of wood smoke?

Wood smoke is the most common source of neighbour complaints about garden saunas, and it is not covered by the particulate figures above. Smoke nuisance can be actionable as a statutory nuisance regardless of smoke control area status.

Sources: DEFRA, Emissions of air pollutants in the UK — Particulate matter (2024 data year). WHO, Global Air Quality Guidelines (2021). UK Chief Medical Officer's Annual Report 2022. GOV.UK, Smoke control area rules. DESNZ greenhouse gas reporting conversion factors.