Comprehensive Review of the Dangers of Volatile Organic Compounds (VOCs) in Sauna Wood Coatings and the Importance of Using Natural Oils

Introduction The sauna, as one of humanity's oldest therapeutic and recreational methods, dates back thousands of years. From ancient civilizations like the Mayans, who created special places for sweating about 3000 years ago, to Scandinavian countries, especially Finland, where the sauna is an inseparable part of their culture, the use of heat and sweating for promoting physical and mental health has always been valued. Modern scientific research has also proven that saunas can reduce stress levels, contribute to cardiovascular health, and induce general body relaxation.

However, just as every phenomenon can have different dimensions, the construction and maintenance of a sauna also require adherence to precise technical and hygienic principles. One of the most vital parts of a standard sauna is the selection of wood materials and the method of coating them. As the main material for building a sauna, wood is exposed to high temperatures (around 70 to 90 degrees Celsius) and humidity fluctuations. These specific conditions make wood susceptible to mold, fungus growth, and cracking. To combat these issues, the use of protective coatings seems essential, but choosing the type of coating can be challenging. The use of inappropriate chemicals containing Volatile Organic Compounds (VOCs) in the closed and hot environment of a sauna can turn into a serious threat to human health. In this article, we will scientifically examine the dangers of VOCs and solutions for maintaining health in the sauna environment.

Anatomy and Structure of the Modern Sauna A dry or Finnish sauna is designed as a cabin with wooden walls, ceiling, and floor, inside of which wooden platforms for sitting and lying down are installed. The choice of wood for sauna construction is not accidental; wood has thermal insulation properties and does not get hot when in contact with the skin. Also, the natural smell of wood in heat gives people a sense of relaxation.

In the past, firewood and charcoal were used to heat the sauna environment, but today, due to greater convenience and safety, electric or gas heaters are used. However, the use of gas heaters requires very precise ventilation to prevent the accumulation of carbon monoxide gas. For this reason, electric heaters have become more common in modern saunas with smaller dimensions. But an important point that is often overlooked is the interaction of hot sauna air with wood coatings. When the temperature reaches 70 degrees Celsius, chemical processes on wooden surfaces accelerate, and if the wood coating is not suitable, it can become a source of toxic pollutant emissions.

Challenges of Wood Maintenance in the Sauna Environment Wood is a living and dynamic material that interacts with its surrounding environment. In the sauna environment, wood faces two main challenges: 1. Moisture and Microbial Growth: Moisture from body sweat or pouring water onto hot stones provides a suitable bed for mold and fungus growth on the wood. 2. Drying and Cracking: Since most woods have a percentage of natural moisture, the high temperature of the sauna can rapidly evaporate the internal moisture of the wood. This causes uneven contraction of the wood texture, warping, and the creation of deep cracks in the wood structure.

To solve these problems, using a protective coating is essential. However, this coating must have unique characteristics. A suitable coating for sauna wood must prevent the entry of external moisture to stop mold growth, but at the same time, it should not prevent the exit of the wood's internal moisture; this property is called "breathability." Also, the coating must be water-repellent so that dirt and stains do not settle on it. But the most important feature is its safety at high temperatures.

What are Volatile Organic Compounds (VOCs)? The term VOCs stands for Volatile Organic Combinations. These are organic chemicals that have high vapor pressure at room temperature. High vapor pressure is associated with a low boiling point and relates to the number of molecules of the substance in the surrounding air. This characteristic is known as "volatility." Simply put, VOCs are substances that easily evaporate from a liquid or solid state into a gaseous state and spread into the ambient air.

These compounds are found in many common household and office items. Chemical paints, sealers, primers (kilr), polyester, polyurethane, cleaners, disinfectants, pesticides, floorings, carpets, compressed wood products like MDF, and even cigarette smoke can all be sources of VOC emissions. The United States Environmental Protection Agency (EPA) has classified many of these compounds as hazardous air pollutants due to their potential to cause adverse health effects. Some of the most common and dangerous of these materials include benzene, formaldehyde, and toluene.

Mechanism of VOCs' Impact on Human Health The entry of VOCs into the body occurs mainly through inhalation. When indoor air quality in homes or closed environments like saunas is endangered by harmful pollutants, blood oxygen levels decrease, and the respiratory system is put under pressure. The concentration of these materials in closed environments is usually much higher than in the open air.

When these materials are released in the sauna environment, the situation becomes critical. High heat increases the speed of evaporation of these materials and causes the lungs to dilate. In the high heat of a sauna, human lungs receive more oxygen to cool the body, and as a result, send a massive volume of toxic gases present in the air directly into the bloodstream and vital organs. This causes the toxic effects of VOCs in a sauna to be several times greater than in normal environments.

Dangers of Using Coatings Containing VOCs in Saunas Unfortunately, in many cases, due to lack of awareness or lower cost, after the construction of the sauna is finished, the woods are coated with inappropriate materials such as varnish (alkyd), solvent-based oils, sealers, primers, polyester, polyurethane, or water-based resins. These materials, even after apparent drying, slowly emit harmful gases at room temperature (a process called Off-gassing).

Now imagine these surfaces are exposed to a temperature of about 70 degrees Celsius. Heat acts as a catalyst and drastically increases the speed of toxic gas emissions. In the small and closed environment of a sauna, where ventilation is also limited (to maintain heat), the concentration of these gases can reach dangerous levels in the shortest time. According to the American Lung Association, many VOCs are associated with causing cancer, and when placed at high temperatures, they can be particularly dangerous for the respiratory system. Using these coatings in a sauna effectively turns this relaxing environment into a toxic gas chamber.

Short-term and Long-term Health Effects of VOC Exposure The damage caused by inhaling these materials can be divided into two categories:

Short-term Effects These symptoms usually appear immediately upon entering the polluted environment or a short time after:

• Irritation of the eyes and respiratory tract
• Headache and dizziness
• Temporary visual disturbances
• Nausea and vomiting
• Shortness of breath in individuals with sensitivities

Long-term Effects Continuous and long-term exposure to these materials can cause irreversible damage:

• Serious damage to the liver, kidneys, and central nervous system
• Increased risk of developing various types of cancer
• Chronic irritation of the eyes, nose, and throat
• Chronic fatigue and sleep disorders
• Loss of muscle coordination
• Memory and concentration disorders

For asthma sufferers or individuals who have previously had sensitivities to certain chemicals, these effects can be very acute and dangerous.

Scientific Solution: Plant-based and VOC-Free Oils (VOC FREE) The only reliable solution for maintaining health in a sauna and increasing the lifespan of the woods is to use coatings that have a plant-based base and are free of volatile organic compounds. These products are called "VOC FREE oils."

Sauna-specific wood oil must be able to create a protective barrier that both stops moisture entry and allows the wood to breathe. Natural plant oils (such as linseed oil, Chinese wood oil, or specific plant compounds) penetrate deep into the wood texture and nourish it from the inside, without creating a non-penetrable plastic layer on the surface. These oils do not decompose at the high temperatures of the sauna and do not emit toxic gases. They also retain their water-repellent properties and prevent the wood from staining.

If chemical coatings or solvent-based varnishes have been used in your sauna previously, it is recommended to definitely proceed with sanding and renewing the wood coating with plant-based oils specific to saunas. This action not only ensures your health but also drastically increases the beauty and durability of the wood.

Frequently Asked Questions (FAQ)

1. Is any type of wood oil suitable for a sauna? No. Many industrial oils contain petroleum solvents and chemicals that become dangerous in heat. You should only use oils that have a label "Suitable for Saunas" or "VOC Free".
2. How do I know if my sauna oil contains harmful materials? Usually, a pungent and chemical smell when the sauna heats up is a sign of harmful materials. Also, if the wood is shiny and plasticized (like the effect of polyurethane), it is likely harmful. Natural oils have a mild and natural smell and show the wood as matte and natural.
3. Are plant oils resistant to mold? Yes. Quality plant oils produced for saunas contain natural anti-fungal materials and prevent mold and fungus growth by creating a water-repellent layer.
4. How often should sauna oiling be repeated? This depends on the amount of sauna usage. Usually, an annual check and recharging of the oil if necessary is recommended.
5. Can regular wood waxes be used in a sauna? No. Regular waxes melt at high temperatures and can become sticky or emit toxic gases. Always use products specific to hot and humid environments.

To view and purchase various types of plant-based and VOC-free (VOC Free) oils specific to sauna wood that guarantee your health, you can refer to the following link:

Buy VOC-Free Interior and Space Wood Oil https://tehranwood.com/product-category/wood-stain/%da%86%d9%88%d8%a8-%d9%81%d8%b6%d8%a7%db%8c-%d8%af%d8%a7%d8%ae%d9%84%db%8c/

 Volatile Organic Compounds from Wood and Wood-Based Panels (Review) — MDPI paper on VOC sources, emissions, and health impact: Read MDPI Review on VOCs from Wood Materials (2020)

 Impact of Wood Treatments on Indoor Air Quality — Conference findings comparing conventional vs sustainable finishes: Indoor Air Quality & Wood Treatments (2025)

 Coated Furniture VOC Emissions Review — MDPI article discussing VOCs from coatings and health risks: VOCs from Coated Furniture Units (2021)

 Natural Oils in Wood Finishing — Research on vegetable oils as safer wood finishes: Vegetable Oils Used as Wood Finishing Substances (Academia.edu)

 EPA Indoor Air Quality & VOCs — Health effects and VOC sources: EPA Overview: VOCs and Indoor Air Quality