Sauna Glossary

AHJ (Authority Having Jurisdiction)

The local body — building department, electrical inspector, or fire marshal — that approves sauna installations and interprets code for your address. Permit requirements for wiring and clearances are set by the AHJ, not the manufacturer.

Aspen (wood)

A light-colored, low-resin hardwood traditionally used for sauna benches and backrests in Finland. Its low resin content means it stays cool to the touch and does not darken as quickly as softwoods.

Auto shut-off timer

A safety feature that cuts heater power after a preset duration, typically 60 minutes, even if the user forgets to switch the sauna off. It is standard on electric heaters and infrared panels.

Barrel sauna

A cylindrical outdoor sauna shaped like a barrel lying on its side. The curved profile reduces air volume, which shortens heat-up time, and sheds rainwater naturally.

Bather capacity

The number of people a sauna is designed to seat at once, determined by bench length and usable interior volume. Manufacturer capacity figures assume seated adults; benches shared by two people need roughly 60 cm (24 in) each.

Carbon heater (infrared)

An infrared panel with a carbon-fiber heating element spread across a large surface area. Carbon panels run at a lower surface temperature than ceramic and produce even, long-wave far-infrared heat across the whole panel.

Ceramic heater (infrared)

An infrared heater built around ceramic rods or plates. Ceramic elements run hotter over a smaller surface than carbon panels, heat up faster, and concentrate output in a smaller area.

Chromotherapy

Colored LED lighting installed inside saunas, marketed as mood lighting. LEDs have no heating function; any wellness claims attached to specific colors lack strong clinical evidence.

Cold plunge

Immersion in cold water immediately after a sauna session, a core part of Finnish sauna culture and modern contrast bathing. Typical home setups use a cold tub, shower, or natural water at roughly 10–15 °C.

Contrast bathing

The practice of alternating heat (sauna) and cold (plunge or shower) within one session. The rapid vascular constriction and dilation is a traditional recovery ritual; research on specific benefits remains mixed.

Dedicated circuit

An electrical circuit serving a single appliance, required for most sauna heaters. Dedicated circuits prevent overloading shared household wiring; infrared cabins of 1,500 W and above generally require one.

Dry sauna

A sauna session without added steam, relying on hot, dry air. In practice almost all electric Finnish saunas are dry unless water is ladled onto stones; air humidity stays below 20 %.

EMF (electromagnetic field)

The invisible field of electrical and magnetic radiation emitted by any powered device, including infrared heaters. Sauna marketing uses "low EMF" to describe heaters designed to keep field strength at the bather’s position low.

Far infrared (FIR)

Infrared radiation with wavelengths of roughly 5.6–1,000 micrometers, the band used by virtually all infrared saunas, blankets, and tents. FIR penetrates the skin surface and is experienced as gentle radiant warmth.

Finnish sauna

The traditional hot-air sauna: a wooden room heated to 80–100 °C by a stove with stones, with low humidity unless steam is added. Finnish sauna culture defines session etiquette, ventilation, and the löyly tradition.

Footprint

The floor area a sauna occupies, given as width × depth. Checking footprint against your room dimensions is step one of sauna planning; the space-planner concept also accounts for clearance distances.

GFCI (Ground-Fault Circuit Interrupter)

A safety device that trips a circuit within milliseconds when current leaks to ground, protecting people from shock. Bathroom and outdoor sauna circuits are normally required to be GFCI-protected by code.

Hardwired

An appliance connected directly to building wiring rather than through a plug and socket. Higher-power sauna heaters (typically above 3 kW) are hardwired by a licensed electrician.

Harvia-grade heater

Reviewer shorthand for electric heaters whose build quality, stone capacity, and output are comparable to those of established Finnish manufacturers such as Harvia. It is a benchmark class, not a formal standard.

Heat-up time

The minutes a heater needs to bring the room or panels to operating temperature. Infrared cabins typically reach target in 10–20 minutes; traditional stoves need 30–60 minutes depending on size and insulation.

Hemlock (wood)

A light, low-resin softwood widely used in infrared cabin construction, especially in North American imports. Hemlock has little odor, which suits bathers sensitive to cedar aroma.

Hot-rock heater

The classic electric or wood-fired Finnish sauna stove: heating elements surrounded by a stone basket. Throwing water on the hot stones creates steam (löyly).

Hygrometer

An instrument measuring relative humidity. In saunas it tracks how much steam has been added to the air; steam rooms run near 100 % humidity while dry saunas stay below 20 %.

Infrared cabin

A walk-in wooden room heated by infrared panels rather than hot air from a stove. Cabins run at 45–60 °C because the panels warm the body directly instead of the air.

kW (kilowatt)

A unit of power equal to 1,000 watts, used for heater output and electrical load. A 2 kW heater running one hour consumes about 2 kWh of electricity.

kWh (kilowatt-hour)

A unit of energy: one kilowatt sustained for one hour. Electricity bills price consumption per kWh, which is what sauna running-cost calculations are built on.

Kiuas

The Finnish word for a sauna stove or heater. In modern usage it covers electric, wood-fired, and gas heaters — anything that heats the stones.

Kiuaskivet

Finnish for sauna stones: the rock bed on a stove that stores heat and flashes water to steam. Peridotite and olivine-diabase stones are traditional because they tolerate thermal shock without cracking.

Löyly

The Finnish term for the steam and heat sensation created when water is thrown on hot sauna stones — and, by extension, the spirit of the sauna session itself. Proper löyly rises as soft, humid waves rather than scalding blasts.

Low-EMF heater

An infrared heater engineered to minimize electromagnetic field strength at the bather’s position, typically via shielded wiring or cancellation layouts. Manufacturers usually quote EMF in milligauss at a stated distance.

mG (milligauss)

A unit of magnetic flux density commonly used in sauna marketing to state EMF levels. For scale, everyday household background at one meter from appliances often measures a few milligauss.

Mid infrared (MIR)

Infrared wavelengths of roughly 1.4–3.0 micrometers, between near and far infrared. Some heaters combine MIR emitters with FIR panels to broaden the wavelength mix.

Near infrared (NIR)

The shortest infrared band, roughly 0.75–1.4 micrometers, closest to visible light. NIR is used in heat lamps and red-light panels; it delivers intense, concentrated warmth perceived as glowing heat.

Off-gassing (VOC)

The release of volatile organic compounds from wood treatments, glues, and finishes when heated. Sauna-grade timber should be untreated interior-grade; strong chemical smell in a new sauna usually indicates finishes not meant for heat.

Plicatic acid

The organic compound responsible for western red cedar’s characteristic scent — and for cedar-dust asthma in heavily exposed woodworkers. Solid cedar in a sauna releases it slowly and is not associated with the occupational dust risk.

Portable sauna tent

A foldable fabric enclosure with an infrared heating panel, used seated with the head outside the tent. Tents pack into a bag and plug into a standard outlet, making them the most mobile sauna form.

Prefab kit

A sauna delivered as pre-cut or pre-assembled panels for on-site assembly, as opposed to a custom-built room. Most home barrel saunas and infrared cabins are prefab kits.

Red-light therapy panel

A device emitting red and near-infrared light (roughly 630–850 nanometers) at low heat output. Panels appear alongside infrared saunas in wellness contexts but work on a light-exposure, not heat-stress, principle.

Sauna blanket

A lie-in far-infrared heating mat shaped like a sleeping bag, with the head outside the blanket. Blankets fold flat for storage and run from a standard outlet.

Sauna hat

A felt or wool cap worn in hot saunas to keep the head cooler during long sessions. It is common practice in Finnish and Russian bathing traditions.

Saunatonttu

The sauna elf of Finnish folklore — the spirit believed to live in the sauna and keep it safe. Traditional etiquette treats the sauna as its own quiet space partly on the tonttu’s account.

Saturated steam

Steam at the boiling temperature of water for its pressure, with no air mixed in. Steam generators deliver saturated steam to the room through a steam head.

Steam generator (kW/volume sizing)

The appliance that boils and pipes water as steam into a sealed room. Sizing rule of thumb: about 1 kW of generator output per 1–1.5 m³ of room volume, with adjustments upward for tile, stone, or exterior walls; every manufacturer publishes a rated maximum volume per model.

Steam room

A bath of 100 % humidity at 40–45 °C, created by a steam generator — the hammam or Turkish-bath model. It is the cool, humid counterpart to the hot, dry Finnish sauna.

Thermowood (thermally modified timber)

Softwood heat-treated at 180–230 °C to improve dimensional stability and rot resistance without chemicals. Thermo-spruce and thermo-pine are standard in outdoor barrel and cabin saunas.

µT (microtesla)

The SI unit for magnetic flux density used in EMF measurement; 1 µT equals 10 mG. Scientific literature typically reports EMF in µT, while sauna marketing uses mG.

Ventilation

Deliberate air exchange in a sauna — fresh air in low, warm air out high — which keeps oxygen levels up and heat even. Good ventilation is a hallmark of Finnish sauna design and prevents stuffy sessions.

Vihta / vasta

A whisk of fresh birch branches (with leaves) used to gently flag the skin during a sauna session, releasing birch aroma. Called vihta in western Finland, vasta in the east.

Western red cedar (wood)

An aromatic, rot-resistant softwood traditional in North American sauna building. Its natural oils (including plicatic acid) give the scent many bathers associate with saunas; some prefer odorless hemlock or aspen instead.

Wood-fired heater

A sauna stove burning logs, common in outdoor saunas and summer cottages. Wood stoves take longer to reach temperature than electric heaters and need a code-compliant chimney.