The appeal of saunas and steam rooms for relaxation and health benefits has made them popular features in gyms and spas. As people returned to shared public spaces, the question of whether these high-heat, enclosed environments are safe from the transmission of respiratory viruses like SARS-CoV-2 became important. Understanding the safety of these public wellness spaces requires a look at how the virus behaves under extreme heat and humidity, and how human behavior introduces the primary risk.
Viral Stability in High-Heat Environments
Scientific studies have consistently shown that high temperatures actively degrade the SARS-CoV-2 virus, which has an outer lipid envelope susceptible to heat damage. The rate of viral inactivation increases as the temperature rises, significantly shortening the time the virus can remain infectious on surfaces. For instance, research suggests that on surfaces, a 90% reduction in viral infectivity can occur in approximately 35 minutes at a temperature of 54.5°C (about 130°F). At 70°C (158°F), the time for significant viral reduction in droplets is estimated to be mere seconds. These conditions make it highly unlikely for the virus to survive for long periods on surfaces within the hot room itself, particularly in dry saunas. However, these laboratory findings about environmental stability do not fully account for person-to-person spread.
Aerosol Transmission Risk in Shared Enclosed Spaces
The main safety concern in any shared thermal room is transmission between people, not the virus surviving on the benches. The risk of infection is overwhelmingly related to close-range exposure to respiratory droplets and aerosols produced by an infected individual. In a small, enclosed space, the ability to maintain physical distance from others is severely limited, which is the primary factor driving transmission risk. Relaxing in a hot environment often involves heavier breathing, which increases the volume and dispersal of airborne particles carrying the virus. If an asymptomatic person is present, their respiratory aerosols can quickly accumulate in the shared air of a poorly ventilated room, elevating the exposure risk for others. Many saunas and steam rooms are designed to be sealed to retain heat or steam, which naturally restricts the necessary air exchange rate for diluting viral particles.
Assessing the Difference Between Saunas and Steam Rooms
The difference in environmental conditions between a dry sauna and a steam room creates different risk profiles. A traditional dry sauna operates at temperatures often ranging from 70°C to 100°C (158°F to 212°F) with very low humidity. This extreme, dry heat is highly effective at inactivating the virus on surfaces quickly, largely eliminating the risk of surface-based transmission. In contrast, steam rooms typically operate at lower temperatures, often between 40°C and 45°C (104°F and 113°F), but with near 100% relative humidity. This temperature range is generally insufficient to guarantee rapid viral inactivation, meaning the virus may persist longer on surfaces and in the air compared to a dry sauna. The overriding concern in a steam room is the lower temperature combined with the high occupancy density.
Essential Safety Guidelines for Visitors and Facilities
Facilities should implement strict operational protocols to mitigate the risk of viral spread.
Facility Protocols
Facilities should limit the number of occupants to ensure physical distancing of at least one to two meters between unrelated groups. Improving air quality is paramount, requiring facilities to increase ventilation to ensure a minimum of six air exchanges per hour. For saunas, using the high heat for 30 to 60 minutes at 71°C (160°F) or higher between use can also serve as an effective disinfection measure for the wood surfaces.
Visitor Guidelines
Visitors have a responsibility to adhere to safety measures to protect themselves and others. Anyone experiencing symptoms of illness, such as coughing or fever, should refrain from using public thermal rooms entirely. Users should always sit on a clean towel to reduce any potential surface contamination and aim to keep their session times short. Limiting use to only individuals within one’s immediate social bubble is another effective way to reduce the risk of transmission in these confined spaces.