Factors of climate are experienced as a whole rather than separately. We feel the radiant heat from the stove, the difference in temperature at the level of the head and feet, air currents, etc all at the same time and all these factors together make up a microclimate. The question here is whether a microclimate can be assessed. Of course, on a subjective level, we immediately evaluate the comfort level of a surrounding microclimate and experience the consequences of its impact on the body but can this experience be measured objectively? Can certain climatic indicators be replicated in order to create a little piece of heaven in the steam room?
Here, traditional equipment used in meteorological research comes to our aid, such as Vernon's globe thermometer (Horace Middleton Vernon, British physiologist and researcher of labour conditions, 1870-1951). In Russia, this instrument is used to produce an environmental thermal load index (ETL). The environmental thermal load index, a composite indicator expressed in °С, characterises the overall impact of microclimate components on the human body (temperature, humidity, air flow speed and heat radiation). Outside of Russia, the globe thermometer is used to determine the so-called WBGT-index (Wet-Bulb Globe Temperature), which also illustrates the effect of a microclimate on the body. ETL index values are so important that they lie at the core of government norms for working conditions, sanitary and construction standards. The globe thermometer characterises human heat transfer in which heat is dissipated into the environment directly via radiation from the skin and by convection (cooling of body heat by air surrounding the body).
So, in our studies, we measured the temperature in the steam room with a dry, a wet (soaked) and a ball thermometer at the level of the floor, the benches and the ceiling, and then, by taking all the parameters into account we arrived at an ETL value (WBGT), a specific "comfort temperature". So what affects the ETL value to the greatest degree? Naturally, it is the temperature of the wet rather than the dry thermometer because this reflects the ease of the body cooling process that takes place when we sweat. As we know, high humidity levels make sweating more difficult and uncomfortable. The least influential factor is the basic room temperature.
When measuring the ETL at different heights from the floor upwards, we averaged out the values obtained. The smaller the temperature difference, the more comfortable it is to spend time in the steam room. To avoid the risk of burns, hot air flow has to be reduced to a minimum.
During our research we took WBGT index measurements in several traditional Russian steam rooms, 'banyas' with huge multi-ton furnaces ('Ussachevsky banyas', 'Gorky 10', spa hotel ‘Zhukova 2', Spa-boutique Sante de la Russie on Mosfilmovskaya St., Moscow and in a private banya in the town of Zheleznodorojhny) as well as in a public sauna equipped with a Finnish electric stove of a well known brand.
The higher the WBGT index measurement, the more pleasant the experience of the steam room. Below are some of the characteristics of the steam rooms we researched:
- Private sauna in the town of Zhelesnodorozhny, dimensions approximately 3x4x2.7 m. The Russian banya stove takes up an entire corner of the steam room. The stove's heating time lasts for approximately 5 hours in winter and 3.5 hours in summer. Once temperature has been reached, the steam room can be used for up to four days when set to family regime. WBGT - 56°C.
- In the Zhukovka-2 spa hotel sauna, all steam room processes are managed by a sauna virtuoso with 35 years experience. The sauna creates a unique steam, in which 110 degrees celsius is barely felt at all and you find yourself never wanting to leave the steam room. The stove was built in 1982 and is gas-fuelled. It has an iron core 3 tonnes in weight. WBGT - 57.5°C.
- 'Ussachevsky banyas', Moscow (10, Usacheva Street). Before our session, the steam room was prepared by a team led by one 'uncle Sasha'. Many regular sauna goers come here because of uncle Sasha's famous steam. The crowded steam room and applause that rings out when customers enter it is testimony to his skilful art. We were able to record the equipment's indicators whilst the clients were applauding. WBGT - 52°C.
- A usual sauna with an electric heater produced in accordance with modern Finnish technology. The physical sensations experienced in the steam room are characteristic of this kind of facility. WBGT - 33.7°C.