First Burn-Off of a New Heater

Why a new heater smells on first use

When a sauna heater is manufactured, the metal surfaces and heating elements may pick up thin films of oil, grease, or protective coatings. These residues come from the forming and machining process, and they are not something you can wipe off easily. The first time you switch the heater on, those residues heat up and vaporize, which produces a smell that many people describe as oily, metallic, or slightly acrid.

The smell is not a sign that the heater is faulty. It is a normal part of the first heat-up cycle. Some heaters also have a thin layer of protective wax or lacquer applied to the outer casing for shipping, and that coating has to burn away too. If your unit has a UL or ETL mark, the safety certification process requires the design to meet the applicable standard, but it does not prevent the normal first-use odor.

The intensity of the smell varies. A small portable heater with a modest coil will produce less odor than a large kiln-dried heater with a thick gauge element. In both cases, the process is the same: the residues burn off, the metal surfaces reach their normal operating temperature, and after one or two cycles the smell is gone. For guidance on selecting a heater that matches your room, see our guide to sauna heaters.

• Heating elements are the most likely source, because they reach the highest temperatures.
• The outer casing, especially if it has a painted or coated finish, can also off-gas during the first heat-up.
• If you bought a heater with stones already packed, the stones themselves are usually not the source of the smell, but any dust on them can add a faint earthy note.

What the smell actually is

The smell is mostly from organic compounds that evaporate when the metal gets hot. These compounds are not present in large amounts, which is why the smell fades after the first cycle. In a closed sauna room, the concentration can build up enough to be noticeable, which is why the usual advice is to ventilate.

Some heaters also have a thin layer of machine oil on the threads or fasteners. That oil can drip or run when it heats up, and it may produce a brief wisp of smoke. Again, this is normal. If the smoke continues after two or three full heat-up cycles, or if it is accompanied by a burning electrical smell, you should turn the heater off and contact support.

What manufacturers usually advise

Most heater manuals include a section on the first burn-off. The exact wording varies, but the common recommendation is to run the heater for a certain period with the room empty. Some makers say open the door, others say keep it closed but open a window or vent. The purpose is to let the vaporized residues escape before you sit in the room.

The Finnleo FAQ notes that a traditional sauna generally takes between 30 and 60 minutes to fully heat up, depending on the heater, the room size, and the outside temperature. For a first burn-off, makers usually suggest running the heater for at least that long, or until the room reaches its normal temperature, and then letting it cool with the door open.

You should check your specific manual for the recommended time, because it varies by heater size and type. A small 4 kW unit may need less time than a 9 kW unit. In general, the process is the same: heat, ventilate, repeat until the smell is gone.

How to prepare for the first burn-off

Before you switch on the heater for the first time, make sure the room is clean and free of plastic packaging, tape, and stickers. Remove any protective film from the heater casing and control panel. If the heater came with stones, they should be rinsed or wiped according to the manual (some makers recommend a quick rinse, others say to brush off dust). For more on this, see our article on washing new stones first.

Open a window, a door, or both. The room does not need to be fully ventilated, but you want a path for the air to escape. If your sauna is in a basement or a room without a window, consider running a fan to push the air out. Understanding basic sauna ventilation can help you set up a proper airflow.

Do not sit in the sauna during the burn-off. The room will be uncomfortable, and the fumes can irritate your eyes and throat. Set a timer so you remember to turn the heater off, and then let the room cool completely before you go back in.

It is also a good idea to wipe down the benches and walls after the burn-off. The vaporized oils can settle on surfaces as a fine film, and a quick wipe with a damp cloth will remove it before your first real session.

What to expect during the first real session

After the burn-off, the heater should be free of strong odors. A very faint smell may remain for the first few sessions, especially if the heater has a thick coating. This is normal and will fade.

If you notice a strong burning smell during a regular session, do not ignore it. A persistent chemical or electrical odor can indicate a wiring issue or a failing component. The Cleveland Clinic notes that saunas are safe if used within reason, and that you should follow the guidelines of the sauna you are in. If something smells wrong, turn the heater off and investigate before continuing. For more on choosing the right heater for your space, see our traditional sauna gear guide.

How long the smell lasts

For most heaters, the smell is gone after the first full heat-up and cool-down cycle. Some thicker coatings may take two or three cycles. Plan for the first burn-off on a day when you have time to complete the cycle and air out the room.

You should also plan for the fact that the first burn-off is not the same as your regular heat-up. During a normal session you would sit in the room, but the burn-off is done empty. It is a one-time step, and skipping it means you will be sitting in the fumes during your first session.

Related topics

The burn-off is just one part of preparing a new sauna. You may also want to read about washing new stones first, the difference between a first burn-off and a regular heat-up, and what to do if your heater smells during normal use.

What to do for your situation

Questions

Is a smell during the first heating normal?

Yes. A new heater often smells during the first heat-up because protective oils and manufacturing residues burn off the elements and metal surfaces. The smell usually fades after one cycle. For more on the process, see our article on first-use burn-in.

Can I sit in the sauna during the first burn-off?

No. The fumes can irritate your eyes, throat, and skin. Run the heater empty, ventilate the room, and wait until the room cools before entering.

How long does the smell last?

For most heaters, the smell disappears after the first full heat-up and cool-down. Some coatings take two or three cycles. If the smell persists, check the manual or contact support.

What is the difference between the first burn-off and a regular heat-up?

The burn-off is done with the room empty and ventilated, and it is meant to vaporize manufacturing residues. A regular heat-up is shorter and is meant to bring the room to temperature for your session.

Do I need to do a burn-off for an infrared heater?

Infrared heaters also have a first-use process, but the procedure may differ because the emitters operate at lower temperatures. Check your manual. Some infrared makers recommend a shorter burn-off with the room ventilated, similar to traditional heaters.

What if I skip the burn-off?

You can skip it, but you will likely sit in the fumes during your first session. The smell is not toxic in the amounts produced, but it can be unpleasant. The better approach is to do the burn-off once and air out the room.

Should I wash the stones before the first burn-off?

That depends on the maker. Some recommend rinsing stones to remove dust, others say to wipe them dry. Check your manual. Wet stones can crack if heated too quickly, so only rinse if the manual says to. For general stone care, see our guide on washing new stones.