Indoor Air Quality vs. Water Quality
Indoor Moisture and How to Combat it
When operating an indoor swimming pool, it must be understood that the indoor pool area is a unique space, which will require a number of special operational considerations. First of all, the pool area is a special room containing a large volume of water that must be continually heated, chemically treated, and cleaned 24 hours a day. Therefore, it is unlike most public spaces, which can be closed down at night and given little attention until the next day.
Indoor air quality is closely related to pool water quality; maintaining water balance and appropriate disinfectant levels will help ensure good air quality. It also minimizes the disinfection byproducts entering the air from the water surface that patrons would breathe in. Proper ventilation inside the pool area is another key component to be aware of, especially if chlorine is used to treat the pool water. Inadequate ventilation that does not sufficiently remove air from the pool area can lead to unhealthy conditions.
The air distribution should include low-level return vents to extract air from the surface of the water. Because exhaust air will have chloramines from the chlorine treatment and also have high moisture content, care must be exercised to vent this air to the outside environment and not into dressing rooms, bathrooms, showers, or office areas. A common practice for indoor facilities is to utilize large floor standing fans to move the air away from the surface of the water. These fans can be positioned to exhaust the air outside through a door or windows.
Because of the pool itself, very high humidity will develop in the room. The humidity generated can have a negative effect on ferrous metals, certain types of composition board, and building material finishes.
To avoid these inherent problems, the educated operator is advised to:
- Reduce the relative humidity level in the natatorium to 50-60 percent.
- Create a negative air pressure, which will be maintained in the natatorium relative to the adjacent spaces.
- Corrosion can be kept to a minimum if specific building materials, components, and finishes are taken into consideration for humidity and/or chlorine vapors.
These performance specifications can be achieved in a number of ways. The most direct is to:
- Provide a dehumidification system that will monitor the relative humidity in the space, dehumidify the air, reheat it to several degrees below the ambient air temperature and drain off the condensate. Such equipment is available in the marketplace as package units, or a system can be built from engineered components.
- Create barriers between the natatorium and adjacent spaces with air locks or at least doorways that will isolate the pool area from other spaces such as locker rooms, weight rooms, running tracks, aerobic exercise studios and, most important, administration offices and lobbies.Select building materials that will not be affected by humidity or chlorine and its by-products. Such materials are glass, tile, stainless steel, epoxy-coated structural steel, concrete, and concrete masonry units.
- Create necessary thermal barriers when the natatorium has common walls and ceiling with the outside temperature.
The air temperature in a natatorium should be maintained at approximately 2 degrees higher than the water temperature. While competitive swimmers – including master swimmers – will prefer a water temperature of 78-80 degrees, most fitness lap swimmers will desire a only slightly warmer temperature.
Indoor swimming pools often have the stigma of being cold with barren walls, a chlorine smell, and reverberating echoes. None of this is necessary today. Acoustics can be emphasized, automatic water quality controllers can help eliminate the chlorine smell, and a more thought-out choice of warm materials and colors will add to the atmosphere of the space, especially if plants are made a part of the interior design. What would you do to make your pool area “warmer?”
This prevention advisor was reshaped from Kevin Post’s blog on Counsilman Hunsaker’s Hydro+Logic. The original blog was based on Natatorium Design. Read the original here: hydrologicblog.com/natatorium-design.
The American Society of Heating, Refrigerating and Air-Conditioning (ASHRAE) standards for ventilation rates (ANSI/ASHRAE Standard 62.1-2013, Ventilation for Acceptable Indoor Air Quality. Also, the MAHC 4.6.2A Indoor Aquatic Facility Ventilation.