by Nina Wolgelenter and Christian Taber, LEED AP
What is invisible to the eye is often still prevalent to the other senses. Indoor aquatic facilities, despite being open and vast, often harbor poor indoor air quality (IAQ), which can result in occupational asthmatic-related issues, throat, nasal, and eye irritation, and other health-related symptoms.
There are several factors that contribute to a natatorium’s struggle to maintain good air quality––ones that have changed over the decades. Despite numerous facilities being more than 30 years old, many of today’s IAQ issues revolve around the type of chlorine used, community water supplies, and tighter building envelopes that trap contaminants indoors, making these facilities unable to perform at the levels expected of them. One constant, however, is the need for air movement to help move the chloramine gases and keep their concentration levels to a minimum in the breathing zone—152 to 203 mm (6 to 8 in.) above the water—where the swimmers have no choice but to breathe in the contaminated air. Further, additional air movement helps reduce condensation and mold buildup, both inevitable in damp environments.
Large-diameter, low-speed fans are popping up more frequently in both new and renovated aquatic facilities, or are simply being installed in existing spaces to increase the effectiveness of ventilation with HVAC systems and provide the much-needed air circulation. The HVAC system ventilates the building by treating the fresh air brought in. However, the ventilation does not always reach the occupants, and is not always efficiently or effectively used.
Dating back to the early 1990s, air circulation was deemed the solution to an increased chloramine problem in an Illinois aquatic center, as no amount of ‘shocking’ was able to reduce the high concentration of chloramines in the pool. (Shocking is a way of super-chlorinating a pool for a short time to help burn the combined chlorine in the water, reactivating the existing chlorine.) Air circulation was suggested by way of numerous floor fans and opening the doors during the shocking process to ventilate the space. According to an article published by the Professional Pool Operators of America (PPOA), fresh air should be forced over the water’s surface to eliminate chloramines and other various chlorination byproducts. (See K. Williams’ 1995/1996 article, “The Basics of Breakpoint Chlorination,” from the Professional Pool Operators of America (PPOA) Pumproom Press.)
Presently, small-diameter, high-speed floor fans are being replaced with ceiling-mounted, large-diameter, low-speed fans as large as 7 m (24 ft) to help circulate the air year-round. This reduced chloramine buildup at the water’s surface and the inevitable condensation issues leading to mold and mildew growth. Regardless of the method used to treat the air, it is important to keep it flowing––without creating a draft––around the space to reduce condensation.
According to the Centers for Disease Control and Prevention (CDC):
The buildup of these irritants in the air is partially due to poor air turnover. The poor movement of fresh air over the pool surface, combined with the use of air recycling devices to control heating costs, leads to poor air exchange.
Even with energy-efficient air-handling units (AHUs) recirculating the air, chloramines are still trapped at the water surface, unable to escape. Air-handling systems must bring a great deal of fresh air and exhaust full blast when the pool is busy. If not exhausted, the chloramines continue to build. If the AHU does not effectively remove chloramines, then a heavily used pool will likely have an air quality problem.
The existing problems that make up poor IAQ can be resolved by combining prevention measures. Improving air movement in the environment and increasing the effectiveness of the air exchange process will reduce irritant levels in the air as well as help with the high cost of conditioning systems.