Anyone who has been around indoor swimming pools knows how awful the air in the room can become if it is not handled correctly.
As swimmers, lifeguards, or pool operators, you begin to dread having to visit facilities that seem to have “out of control” air quality issues. Our noses revolt, our eyes water, and our lungs begin to burn. Many of us have cold or allergy symptoms for days after even the briefest of visits to such facilities.
“Aquatic facilities with poor air quality are not just offensive to the senses, they can be dangerous to our health.”
At the Center for Disease Control and Prevention (CDC), this issue has become one of serious concern. As part of a new Model Health Code developed to deal with Recreational Water Illness (RWI), CDC is paying very close attention to air quality around indoor swimming pools. CDC realizes that many of the biological and chemical substances that are of concern while in the water, are just as dangerous once they become airborne in the room.
The most prevalent air quality issue facing indoor swimming pool facilities is that of airborne chloramines. Although infectious biological organisms such as Legionella can spread through an indoor pool environment as well, the dreaded offender at any indoor swimming pool is the excessive “chlorine odor.” Where there is chlorine odor, there are airborne chloramines causing discomfort at best, and sickness and corrosion of equipment at worst.
Best practices to control chloramines include approaches to control their formation in the water and approaches to “break-up” or destroy chloramines once they form in the water. It must be understood however, that neither of these approaches will keep chloramines from forming in the swimming pool. These methods attempt to minimize chloramine presence in the swimming pool, but by their very nature, chloramines will form when people get in the pool. Chloramines will then “off-gas” into the air surrounding the pool.
This leads us to the discussion of what to do with the chloramines that will inevitably form and become airborne. Before exploring this topic in detail, there are important facts about chloramine-laced air you must know. The main fact is that chloramine air is much heavier than clean air. Because of this, the offensive chloramine air tends to remain low in the room close to the pool water surface where it initially formed.
To understand this fact one only needs to be in a pool where while standing you can detect a chlorine odor. If you put your face nearer the pool water surface, you will smell a much stronger chlorine odor. This is purely due to the denser, or heavier, chloramine laced air draping low in the room like a weight around the neck.
Another important fact is that lighter air will move quicker and easier through a room than heavier chloramine-laced air. This makes the air in a natatorium prone to “short circuiting.” Short circuiting is the phenomenon whereby only the lighter, easier to move, air is returned to the HVAC system and clean fresh air from outside only replaces this lighter air while leaving the heavier chlorine smelling air behind. Over time, short circuiting of air causes overwhelming buildups of chloramine-fouled air.
You can often identify facilities that have major airborne chloramine problems by the sight of big floor fans deployed in a mostly futile attempt to blow smelly air out through exterior doors. Any time you see this you should also imagine dollars floating out the door with the air (most of which is actually clean air since chloramine air is harder to move) in the form of wasted energy and patron dissatisfaction costs.
One way we designers in the past would prevent “short circuiting” of air was to blow large quantities of clean air from outdoors through the HVAC system and across the water surface, thus pushing the heavier air up into the lighter air for removal by the HVAC system. There are two main drawbacks with this however.
The first drawback with using the “whole room” HVAC system to remove heavy, low-lying chloramine air is that developing enough momentum to move the heavy air often requires high air velocities that may make swimmers colder and uncomfortable. The second problem is the fact that we are moving nasty air higher in the room where it becomes offensive to even more people in the room before being removed by the HVAC system.
While these problems are related to physically moving the air, an even larger drawback is that using “whole room” air exchanges through the HVAC system to remedy chloramine issues requires a lot of excess energy. Each time air is replaced in the room, that air must be reconditioned to the temperature and humidity requirements of the room. Since temperature and humidity directly affect patron comfort and the rate of water evaporation from the pool, these parameters must be maintained precisely for optimum performance. When new air is introduced into the room, that air must be adjusted to the proper environmental levels, which translates into a lot of wasted energy/money.
So, you may be thinking that the problem is just too great to deal with. Not really.
If we look at the nature of chloramine laced air being heavier and denser than cleaner air in the room, we actually have an opportunity to remove the offensive air in a more efficient manner.
Since the chloramine air hangs like a weighted mass near the water’s surface, if we draw the bad air out of the room from points very close to the water surface where this air naturally concentrates, we can deal with the problem effectively and cost efficiently.
The closer to the water surface we can remove this heavier air, the more we can use the weight of the air itself to ensure we are only removing bad air and not good air from the facility. Remember, any air we remove from the room has to be replaced with air from outside of the room. Replacement air is what costs so much money to bring up to temperature and proper humidity levels. The less air we have to replace, the less energy/money we will use.
When properly designed for the room, a system like the Evacuator can effectively remove just enough of the low lying air to eliminate the chloramine problem, while the room’s conventional HVAC system can focus on turnover of the less offensive air and conditioning the space to the proper temperature and humidity levels. With this approach, air quality will be pleasing to your patrons, and energy costs to obtain this safe, pleasing air will be minimized.
During design of air handling systems to remove chloramine laced air, we always evaluate the prospect of heat recovery from the air before it is exhausted from the building. In many cases, it proves cost effective to install such additional equipment as well.
The bottom line for anyone who owns, operates, or is planning an indoor aquatic center is that great air quality is a must for a successful facility, and it is easily obtainable through design and implementation of the proper systems. As a long time aquatic facility engineer, I know that a chloramine evacuation system, paired with the right HVAC system, is the wave of the future and will be the standard by which all facilities will be measured.
There is no reason for an indoor aquatic center to suffer the effects of poor air quality. We can design systems to make poor air quality a long lost nightmare that no one has to experience again.
The video below illustrates how chloramine laced air is removed from a natatorium via an Evacuator system.