Can I burn any wood with a hot tub smoke filter?

The ABCAT® HOT TUB has been developed to be used with suitable firewood. By using the right type of wood, you ensure optimal combustion, less smoke and preserve the smoke filter.

Suitable fuels

The following fuels are suitable for use with an ABCAT® HOT TUB:

• Piece of wood with a circumference of up to 30 cm and a moisture content of 12— 15%
• Briquettes made of pressed, clean wood without additives (such as adhesives)

These fuels ensure a stable fire and clean combustion, so that the smoke filter functions optimally.

Unsuitable fuels

The following fuels are not suitable for use with an ABCAT® HOT TUB:

• Coal (due to compounds containing calcium)
• Brown coal (due to sulphur smell)
• Pellets (due to the high proportion of fly ash)
• Treated wood (preserved, glued, painted or impregnated)
• Wood with nails, screws, or metal

Using these materials can lead to damage to the stove and smoke filter, excessive smoke formation and unhealthy emissions.

Types of wood

Explanation of the table

The types of wood used in red are indicated, will be as unsuited considered. This is due to the high concentration of fragrances that are released during combustion and are generally experienced as unpleasant.

The types of wood used in orange whether red are marked, are less suitable to burn. There are several reasons for this:

• They produce a relatively large amount ash and particulate matter;
• They gasify too fast in a conventional stove, which releases a lot of unburned wood gas;
• They include lots of resin, which causes additional soot formation;
• They give during combustion strong or pungent smells off.

Exotic woods, such as tropical hardwoods, can give off an exotic scent, but this is often used as irritating or annoying experienced by the resins that are released during combustion.

Small pieces spruce wood are suitable for lighting the fire, because they catch fire quickly. As the main fuel, however, they are unsuited: they burn too fast, causing a lot of smoke and emissions. Most heaters simply cannot keep up with this rapid combustion.

Wood moisture and yield

Fresh wood contains 50— 75% moisture; well-dried wood only 12— 15%.
Damp wood lowers the temperature in the stove, causes poor combustion and creates smoke and condensation in the chimney.

💡 Example:
600 grams of beech wood with 15% moisture still contains 90 ml of water. Dry wood = more yield, less smoke.

Splitting and drying wood

Chop wood preferably while it is still fresh, into pieces with a circumference of up to 30 cm and a length of 25—30 cm.
Wood dries at the end - so shorter blocks dry faster.

Place wood outside, preferably under a roof, with plenty of space between stacks and at least 30 cm from the ground.

Wood dries by wind, not sun.

Never keep damp wood indoors (such as in a garage) to prevent mold from forming. However, well-dried wood (12— 15% moisture) can be safely stored indoors.

Measuring wood moisture

Use a wood moisture meter to check that the wood is ready to burn.
Split a log in half and measure three points across the wood grain.
Add up the percentages, divide by three — the average is between 12— 15%, then the wood is suitable.

More information about moisture measurement can be found in the ABCAT® HOTTUB Handbook.

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Summary

✅ Use dry, clean log or wood briquettes
❌ Avoid treated wood, coal, pellets, or wet wood
🌬️ Store wood outside, well ventilated and protected from rain
💧 Control the moisture level (12— 15%) for optimal combustion

📘 More information
Read more about wood types, heating tips and maintaining the smoke filter in the ABCAT® HOTTUB Handbook.

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