Air Quality Challenges

Natatoriums face unique air quality challenges due to disinfection byproducts, humidity, and the enclosed environment. Understanding contaminant sources and control strategies is essential for designing healthy indoor swimming facilities.

Contaminant Sources

Disinfection Byproducts (DBPs)

Chlorine-based disinfectants react with organic matter:

Organic Sources:

• Sweat, urine, skin cells
• Cosmetics, lotions, sunscreen
• Hair and body oils
• Fecal contamination

Chemical Formation: $$HOCl + Organic\ Nitrogen \rightarrow Chloramines$$

Chloramine Types

Trichloramine is the primary air quality concern, accumulating in the breathing zone above the water surface.

Other Contaminants

Trihalomethanes (THMs):

• Chloroform most common
• Formed from chlorine + organic matter
• Carcinogenic concerns

Carbon Dioxide:

• Swimmer exhalation
• High occupancy during events
• Contributes to “stuffy” perception

Health Effects

Respiratory Issues

Chloramine exposure causes:

• Eye, nose, throat irritation
• Coughing and wheezing
• Aggravated asthma
• “Lifeguard lung” (occupational)
• Swimmer’s respiratory symptoms

Exposure Limits

No regulatory standards specific to natatoriums, but guidelines suggest:

Vulnerable Populations

Higher risk groups:

• Competitive swimmers (high exposure)
• Lifeguards and instructors (occupational)
• Asthmatics
• Children (higher breathing rate)

Ventilation Strategies

Source Capture

Exhaust air near water surface where chloramines concentrate:

$$C_{breathing} \propto \frac{Evap\ Rate \times C_{water}}{V_{air} \times ACH}$$

Effective Approaches:

• Low-level perimeter exhaust
• Deck-level return grilles
• Continuous exhaust operation

Air Distribution

Supply Air:

• Introduce high (ceiling or high wall)
• Direct across pool surface
• Maintain 25-50 fpm at water surface
• Avoid direct air jets on swimmers

Return/Exhaust:

• Low wall (12-18" above deck)
• Multiple locations around perimeter
• Continuous during occupied hours

Outdoor Air Rates

Higher outdoor air dilutes contaminants:

Air Change Rates

Water Quality Management

Source Control

Reduce DBP formation through water treatment:

UV Systems:

• Breaks down chloramines
• Reduces combined chlorine
• Requires adequate dose (40-60 mJ/cm²)

Ozone Treatment:

• Powerful oxidizer
• Reduces chlorine demand
• Combined with chlorine residual

Advanced Oxidation:

• UV + hydrogen peroxide
• UV + ozone combinations
• Enhanced DBP destruction

Water Chemistry

Maintain proper balance:

• Free chlorine: 1-3 ppm
• Combined chlorine: <0.4 ppm
• pH: 7.2-7.8
• Total alkalinity: 60-180 ppm

Bather Hygiene

Pre-swim showering reduces:

• Organic loading
• DBP formation
• Required chlorine dose

Many European facilities require thorough showering before pool entry.

Monitoring and Control

Air Quality Monitoring

Continuous Monitoring:

• Relative humidity
• Temperature
• CO₂ (occupancy proxy)

Periodic Testing:

• Chloramine levels
• THM concentrations
• Particle counts

Sensing Technologies

Demand-Based Ventilation

Adjust ventilation based on:

• Occupancy level
• Activity intensity
• Measured air quality
• Time of day

Design Best Practices

Facility Layout

• Separate pool hall from lobby/spectator
• Positive pressure in viewing areas
• Isolated HVAC systems
• Direct exhaust paths

Equipment Selection

• Corrosion-resistant materials
• Dedicated natatorium AHUs
• High-efficiency filtration
• Energy recovery capability

Emergency Provisions

• Alarm on high chloramine
• Emergency ventilation boost
• Evacuation procedures
• Incident documentation

Code and Standard Requirements

ASHRAE Standards

• ASHRAE 62.1: Ventilation rates
• ASHRAE Handbook—HVAC Applications: Natatorium chapter
• ANSI/ASHRAE Standard 90.1: Energy efficiency

Health Guidelines

• CDC Model Aquatic Health Code (MAHC)
• State and local health codes
• Pool and spa industry standards

Addressing air quality challenges in natatoriums requires integrated approaches combining ventilation design, water treatment, and operational practices to protect swimmer and staff health in these unique indoor environments.

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