There are many variables concerning the air temperature and humidity levels in an indoor pool.  The following information is backed by research data from our USA Swimming preferred provider Desert Aire (the largest HVAC manufacturers for pool room heat and dehumidification) as well as personal experience and antidotal evidence.
Decades ago when most pools were 4-lane, 20-yard tanks in the basement of brick buildings, it was observed that the air was easier to breath when the water and air temperature were within a couple of degrees of each other. From this common sense observation parameters were developed. At the time boilers heated most indoor pools and the water temp was always around 84 degrees. The air handling systems were usually steam (hot water) and there was really no such thing as dehumidification. So bringing steam heat (no forced-air) into a room with the thermostat set at 74 degrees F (23 C) was no problem. There was no draft and by the time the air contacted the warmer water, the room temp leveled out about 78 degrees F (25.5 C).
Now we are in the age of forced-air gas or electric heat and steel buildings rather than brick and mortar. The steel is susceptible to moisture and the air has to be dehumidified.  It’s a new ball game but some are still trying to play by the old rules. We would like to give a formula, but the systems vary too much as does the air duct configuration. Even warmer air blowing across the client’s wet body can be uncomfortable. So we have come full circle to using common sense supported by pages of formulas and calculations.
Here are the basics:

  • Room size – the larger the room the harder it is to find a comfortable air-water temperature balance.
  • Pool size (surface area) - the more surface area the more the water will heat the air and add humidity.
  • Pool agitation and bather load – the more jets and bubblers and the more people splashing, the more interaction between air and water.
  • Chemical treatment of the water – the type and brand of chemicals greatly affects air and water quality.
  • Type and size of filter – the more efficient the water filtration the better the air quality.
  • Type and brand of Heating Ventilating Air Conditioning (HVAC) system and dehumidification system.
  • Pool patrons – the age, abilities of clients as well as the type of programming will influence how the temperature is perceived and accepted (e.g. high intensity exercise & therapy/rehab; children or seniors & active young adults, etc.)
  • Use of medium pressure Ultra Violet (UV) technology.

Because of these variables there can be no “set formula” to calculate air temperature for an indoor pool.
Other related issues:
Almost every properly designed pool room is designed to have a negative pressure. That means there is more air being exhausted than is being brought in. If there is a steam room or sauna adjacent to the pool room, every time someone opens the door of the steam room or sauna, hot moist air immediately is being drawn into the pool room.  This is behind the perception of “heavy air.”  It is humid warm air.
Other than people with acute respiratory problems, fresh humid air should not be problematic. Problems occur from the pool evaporation if the water is not balanced properly causing Chloramines to be released into the air. The result can be potential health risks, such as “Lifeguard Lung” and bronchial irritation. This problem is common across the country and has a few solutions, although one solution is a medium pressure Ultra Violet pool water treatment system. Be aware that there is an easy water test to check Chloramines called the “free and available chlorine comparison”.

In conclusion, you are right to be concerned about the relationship between water and air quality and temperature.  If the water is 83-86 F (28-30 C), keep the air at 78-80 F (25.5 – 26 C) and keep drafts off of clients in the pool. In addition, have the HVAC filters checked every 3 months and check water chemistry at least twice a day.

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