Improving Indoor Air Quality

In December 2005, 14 people were killed and 11 more were injured in a Russian indoor swimming pool when a concrete ceiling, supported by stainless steel rods, collapsed (Associated Press, 2005). The conditions that led to this incident and other similar aquatic facility catastrophes can be traced to stress-corrosion cracking that develops due to poor air-quality management within the facility (Dumas, 2006). In natatoriums with “modern,” energy-efficient air handlers, recirculation of conditioned air makes it difficult to rid the building of harmful chloride-ions and chloramines that can cause stress-corrosion cracking to occur.

Facility managers and pool operators must learn to understand the delicate relationship between the active water chemistry, the influence it has on air quality and the distribution of potentially bad air through the ventilation system. Improper management can contribute to catastrophic structural failure, untimely structural rebuilding and human sickness, while proper management will contribute to a healthy and safe environment.

Defining The Problem

Indoor pool facilities, or natatoriums, differ in design, construction and maintenance requirements from all other recreational structures (Williams, 2006). Natatoriums have three interacting components–the water, the indoor air, and the ventilation system. Balancing these interdependent components makes natatoriums difficult to manage. Consequently, it is imperative that aquatic facility managers understand the interaction of these elements inside a natatorium, including relative humidity, ambient air temperature and water temperature, all of which contribute to overall air quality, and how the air circulation system affects air quality.

As chlorine disinfects and reacts with organic compounds, like dirt, urea and body oils, typically introduced by swimmers, it produces natural byproducts. The primary byproducts produced in a gaseous form are commonly called chloramines. When this occurs at outdoor pools, the chloramines rise into the atmosphere and are carried away by air movement. However, when this occurs inside a natatorium, as shown in Figure 1, the chloramines are trapped inside the building until the ventilation system can exhaust them, A buildup of chloramines causes the offensive “pool smell” that not only is harmful to humans, but also can compromise the structural integrity of the building. Current energy-saving practices, like recycling of the air, promote high levels of chloramine buildup, decrease the breathable air quality, and increase contact with structural steel. In addition, when high levels of humidity are allowed to condensate, the impact of chloramines greatly increases the potential for corrosion.

Humidity Is Relative

In the natatorium, humidity control is one of the most important objectives (Williams, 2006). The operator must be aware of and minimize excessive moisture buildup, as it can increase health risks and condensing on surfaces, causing devastating effects on the infrastructure and fixtures. Condensation is an aggressive form of water and contributes to both concrete and metal degradation, which can eventually compromise the building’s integrity. If any chlorine compounds, like chloramines, are in the air, these molecules will find their way into the moisture and significantly enhance the damage created by condensation.

In a typical natatorium, relative humidity should be maintained around 50 percent (Osinski, 2006) in order to prevent increased health risks associated with humidity levels below 40 percent and above 60 percent. The target level is complicated because swimming pools continue to generate moisture, even when people go home for the night. It takes less than 30 minutes for the relative humidity of a natatorium to increase to well over 80 percent if the ventilation and dehumidification system shut off (Xie and Copper, 2006). Managers and operators must understand one can never turn off the air-recirculation system.

Temperature Control

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