Increased Popularity of Natatoriums, Aquatic Centers and Indoor Pools

Televised Olympic swimming has fostered a dramatic increase in the number of aquatic centers around the world. Universities, high schools and communities of all sizes now feature indoor swimming facilities called natatoriums.

Natatorium (plural, natatoria) is “a building containing a swimming pool . . . In Latin, a cella natatoria was a swimming pool in its own building.” Many natatoria also house locker rooms, diving tanks and workout facilities.

With the recent increase in natatoriums around the globe, special attention must be given to the health effects of indoor air quality. Owners of such facilities must be more diligent than ever in providing adequate airflow in their facilities and providing ways to bring in fresh air and exhaust contaminated air.

Most Important Goal of a Pool Air Handling System

While occupant comfort is important, designers and owners of indoor swimming facilities realize that removing chloramines – chlorine that binds to water contaminants forming chemical called dichloramine and trichloramine is the ultimate goal of their air handling systems.

The chloramines off-gas into the air surrounding the pools and are a known cause of respiratory ailments and can also corrode metals in ladders and other structures.

The Center for Disease Control and Prevention says, “Chloramines can build up in the water,” which means they can also build up in the air above swimmers (the breathing space). If there is not enough fresh air surrounding pools, swimmers, employees and spectators are continuously exposed to chlorine and other dangerous contaminants.

This is particularly true for indoor aquatic facilities where air-handling systems are not bringing in enough fresh air and exhausting enough chloramine-polluted air, which is exaggerated in colder winter months and hotter summer months when HVAC systems are working overtime.

ASHRAE  Ventilation Requirements for Indoor Pools

Recognizing the importance of moving air into, out of and around indoor swimming facilities, the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) published a comprehensive article on the subject in July of 2017. Article authors Gary Lochner and Lynne Wasner say that “Healthy and durable indoor pool environments require a well-designed ventilation system with effective air distribution and sufficient outdoor and exhaust air to remove toxic and corrosive chloramines from the space.

They know that natatoria present especially difficult environments for air movement due to the high ceilings and numerous areas where air can become trapped and/or layered.

Airius® Fan Systems Move Contaminated Air

This natural phenomenon of stacked air is called stratification. The Air Pears from Airius® can be positioned to destratify air from ceiling to floor and wall to wall much more efficiently than typical HVAC systems and fans.

The revolutionary Airius series of thermal destratification fans are specifically designed to continuously re-circulate and redirect fresh air throughout natatoria of all types and sizes. Using a patented process, Airius fans directly target stratified and stagnant areas by delivering “columns of air” from heights up to 125 feet.

The Airius® destratification process results in increased air movement for swimmers and spectators alike as the fans can be placed in such a way that they can mix high levels of chlorine contaminated air often found at pool surfaces. By mixing and diluting the chloramines near the breathing level, the air handling system can then exhaust the noxious compound.

Calculating Air Rates and Designing the Best System for Moving Air

The ASHRAE article goes on to describe all the various factors that make it difficult to accurately calculate air flow such as pool type, activity, ceiling heights, air supply and return airflow rates and air distribution complexity and effectiveness.

Airius fan systems can be positioned in multiple areas within a swimming facility to quickly and efficiently move contaminated air out of stagnant spots, from pool surfaces and into areas where the exhaust fans can remove the dangerous air from the building.

Prevent Stratification and the Formation of “Dead Spots”

To prevent air stratification and the formation of “dead spots,” which can lead to trapped chloramines and corrosion, the authors recommend the installation of improved air handling systems. Within the tall spaces of a typical indoor aquatic center, there are multiple “micro-zones” and “dead spots” where the air is trapped.

One of the biggest areas of concern is the “breathing zone” just above the swimmers’ heads. Moving the contaminated air away from these areas and replacing it with clean, fresh air is a natural benefit of the Airius system.

As the article points out, proper air distribution in an indoor aquatic facility:

  • Prevents condensation, corrosion, and stratification;
  • Removes airborne disinfectant by-products such as chloramines;
  • Provides effective mixing throughout the space; and
  • Delivers fresh air to the breathing zones of swimmers, people on the deck, and spectators.

Supply Air Distribution

The authors point out that “the design of the supply air distribution system for an indoor pool is complex because it can have several micro-zones with specific needs for total and outdoor airflow.

This concept of “supplying air to the breathing zone” means an air handling system must be able to continually re-direct fresh air just above the pool surface while moving the contaminated air to exhaust fans that will expel the contaminated air.

A fresh supply of air must also be directed into the deck areas where swim teams, lifeguards and others stand for extended periods. Additionally, fresh air must be specifically directed into the spectator seating area for comfort and at exterior walls to prevent condensation.

With the ability to remotely control the air flow, the Airius fans can be easily installed exactly where they are needed and redirect air on demand.

To paraphrase the article, “exhaust air should be incorporated into the pool air handler and mixed with upper-level return air before connection to the air-handling unit.” This concept is an effective way to remove chloramines, and when combined with proper ventilation air, can serve to continually clean all the air in a natatorium. Air movement systems like Airius will provide a much cleaner environment for swimmers and spectators because chloramines are displaced and moved away from where swimmers breathe.

In the higher levels of the facility, return points should be located to promote mixing of captured air with fresh air resulting in less condensation and corrosion. Airius units can be strategically located next to supply diffusers which prevents the “short-circuiting” of supply air directly back into the return.

Supply Air Delivery Rate of Six Air Changes Per Hour Recommended

To meet the needs of air distribution in a natatorium, ASHRAE suggests that the supply air delivery rate be between 4 and 6 ACH (air changes per hour). This is easily accomplished with the assistance of an Airius fan system because it can direct air into specific locations in the building.

Spectator Areas Easily Targeted with Airius fan Systems

Because spectator seating areas are usually placed well above pool decks, they may require dedicated air handling systems. When properly incorporated into the overall system, Airius units can provide much better ventilation and air distribution than traditional HVAC systems.

Most indoor facilities have budgetary constraints and cannot justify installing a full system just for spectator comfort. The Airius system provides an excellent alternative to a dedicated air handling system just for the spectator area and can again save money over conventional systems.

Regulating the Outdoor Air Portion of the Supply Air

The air being returned from inside the swimming areas to the air-handling equipment is inevitably contaminated with chloramines and other pathogens. Before resupplying air back into the facility, the air-handling unit must then mix a specified amount of outdoor air with the exhaust air to help create a healthy environment.

The system must also regulate moisture in the return air to maintain a proper “space humidity set-point.” Because most indoor swimming pools have large amounts of glass, dealing with condensation can also challenge most HVAC systems. Well positioned Airius units can direct air at exterior glass curtain walls to mitigate condensation.
Reduce Overall Energy Costs with an Airius® System

While Airius® originally developed their destratification technology to reduce heating costs, they learned that they could also move the air trapped in ceilings and other areas of aquatic facilities around as required. When these systems are installed in aquatic centers, owners can save up to 30% on overall HVAC energy costs. The Airius units are easily positioned to force cooler air directly into the hot spots created by traditional HVAC systems and move contaminated air away from swimmers and spectators.

Numerous studies have shown that thermal stratification is the single biggest waste of energy in all buildings and especially so in buildings with high ceilings like indoor aquatic centers. Besides directing air flow to where it is needed the most, the Airius system improves the overall efficiency of heating systems in the winter and cooling systems in the summer. Once installed, the systems begin reducing overall heating and cooling costs.

By helping to maintain more constant temperatures and humidity inside swim centers, the Airius system usually pays for itself within one to three years of operation.

Specific Benefits for Indoor Pools

Since its release in 2004, the Airius System has been the go-to solution to combat thermal stratification in buildings around the world. Available in several models, the Airius fans are suitable for use in buildings with ceilings from 8 to 125 ft. and are available in off-white, grey, or black. Benefits for swimming facilities include:

  • Up to 35% reduction of heating costs
  • Up to 30% reduction of cooling costs
  • Dilute and disperse chloramines at the breathing zone
  • Increased comfort and safety for swimmers, employees and spectators
  • Maximize the efficiency of all types of HVAC systems
  • Simple installation in multiple areas to improve air flow and remove contaminants
  • Utilizes process heatand solar gain
  • Reduced run time on existing HVAC equipment
  • Reduced internal condensation and wet floors
  • Reduced ceiling temperatures increasing lighting lifespan
  • Photohydroionization (PHI) units help mitigate odors, viruses, bacteria and VOCs


Air stratification and dead zones occur in all buildings and are especially challenging in large indoor facilities like natatoria. While traditional HVAC systems deliver solutions for “conditioning” the air inside aquatic centers, they are less efficient at moving the contaminated air away from swimmers and spectators and producing safer and more comfortable environments.

Airius® fans use a patented process to directly target dead zones and deliver “columns of air” from heights of up to 125 feet directly to the areas where they are needed the most. Airius systems can be mounted wherever they are needed, can be controlled remotely at variable speeds, and are easily incorporated into Building Management Systems.



Read More at Airius Fans