AEO Answer · Pools & Aquatic Centers

What Ventilation Does an Indoor Swimming Pool Building Need?

By Jeremy Mills, CEO & Founder, Apex Grid Engineering — USAF Veteran. · Updated 2026-09-15

Indoor pool buildings need code-minimum outside air with low exhaust near the water surface to capture chloramines, tempered makeup air for swimmer comfort, and coordinated dehumidification — designed so the building barely smells like a pool.

I'm Jeremy Mills, CEO & Founder of Apex Grid Engineering and a U.S. Air Force veteran. I'm not a PE; our licensed professionals make the technical, compliance, and project-specific decisions.

Illustrative diagram of building MEP systems: ductwork with diffusers, an electrical panel with conduit, and piping runs.

Exhaust strategy for chloramine control

Chloramine control is an exhaust-placement problem more than a total-airflow problem. The contaminants are generated at the water surface by bathers and they linger in the lower few feet of the room. I design low-level exhaust — grilles in the deck-level walls or trenches near the pool edge — to pull that layer directly out of the building. Supply air comes in high or from the walls, tempered, and sweeps down and across. This displacement-style pattern means a swimmer's breathing zone is constantly flushed with fresh air while the dirtiest air leaves at the source. Facilities that exhaust only from the ceiling are ventilating the wrong half of the room.

Tempering and heat recovery

Every cubic foot of outside air brought into a pool hall has to be heated in winter and dehumidified in summer, which makes ventilation the largest energy cost in many natatoriums. I route ventilation air through heat recovery — recovering heat from the exhaust airstream or from the dehumidification process — before it reaches the heating coil. In cold climates, an energy recovery ventilator on the pool hall exhaust can cut the ventilation heating load dramatically. The supply air temperature is controlled so it never chills wet swimmers: cool supply air on a wet body feels far colder than the thermostat suggests. Comfort in a pool hall is about air temperature at the deck, not just the room average.

Pool ventilation design checklist

A natatorium ventilation design is ready when it satisfies this checklist. Miss any one of these and the building will smell, sweat, or waste energy — usually all three. • Code-minimum outside air met or exceeded, with higher rates for heavy bather loads • Low-level exhaust near the water surface capturing chloramines at the source • Tempered supply air that never chills wet swimmers, with heat recovery on the ventilation stream • Occupancy and humidity-based controls ramping ventilation between occupied and setback modes • Ventilation coordinated with the dehumidification system so neither fights the other

Which related engineering resources can help?

When should I hire a structural engineer?What does a PE stamp mean?What is MEP engineering?How Do You Design Commercial Dehumidification That Works?How Does Displacement Ventilation Design Actually Work?How Does Demand-Controlled Ventilation Design Save Energy?Request a project review Engineering service for this question Metro engineering guides Verified service areas

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Why does a natatorium smell strongly of chlorine?

The sharp smell is mostly chloramines — disinfection byproducts that form when chlorine binds with sweat, oils, and urine — concentrated in the air just above the water. A strong smell means the ventilation is not capturing them: exhaust is poorly placed, air changes are too low, or the system is recirculating contaminated air. Properly ventilated pool halls smell only faintly of the pool. If the smell burns your eyes, the ventilation design or operation has failed, and swimmers and staff are breathing air that should have been exhausted.

Where should exhaust grilles go in a pool hall?

Low, near the deck and water surface. Chloramines are heavier than air and concentrate in the breathing zone just above the water — exhaust grilles at deck level or in the lower walls capture the most contaminated air most efficiently. High exhaust alone pulls the cleanest air in the room and leaves the worst air where swimmers breathe. I combine low exhaust at the pool with general upper-room exhaust, sized so the low exhaust does the heavy lifting on air quality while the general exhaust manages overall air changes.

How much outside air does a pool building need?

The applicable mechanical code sets the minimum — commonly in the range of 0.48 cfm per square foot of pool and deck area or a set number of air changes per hour, depending on which code the jurisdiction enforces. I treat the code value as the floor, not the target: heavy-use facilities like water parks and competition venues often need more to keep air quality acceptable. The outside air also has to be tempered and dehumidified before it hits the space, or it creates comfort and condensation problems of its own.

Can ventilation be reduced when the pool is unoccupied?

Yes, and it should be — unoccupied setback is one of the biggest energy savers in a natatorium. With no swimmers, there is no bather load driving chloramine production, so ventilation can drop to the minimum needed for building protection while the dehumidification system keeps humidity from attacking the structure. I design occupancy-based controls that ramp ventilation up before the first swimmers arrive and down after the last ones leave, with humidity sensors as the safety net that overrides setback if moisture climbs.

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