That strong chlorine smell at an indoor swimming pool might not mean what you think it does. In many cases, the familiar “pool smell” is actually caused by chloramines, compounds that form when chlorine reacts with contaminants introduced by swimmers.
The Centers for Disease Control and Prevention (CDC) has published guidance to help commercial pool operators prevent chloramine buildup, improve indoor air quality, and reduce irritation experienced by swimmers and staff.
We’ve summarized the most important recommendations for commercial pool operators, aquatic directors, facility managers, and maintenance professionals. You’ll find a link to the complete CDC resource below.
1. Understanding Chloramines
- How chloramines form: Chlorine reacts with contaminants such as perspiration, urine, skin cells, and other substances introduced into swimming pool water.
- The familiar pool smell: A strong chlorine-like odor is often associated with chloramines, rather than an excessive concentration of free chlorine.
- Health concerns: Chloramines can cause eye, skin, and respiratory irritation, especially when they accumulate in indoor pool environments.
- Indoor exposure: Airborne chloramines can concentrate near the water’s surface, where swimmers and employees may experience prolonged exposure.
2. Monitor Combined Chlorine Levels
- Test free and total chlorine: Both measurements are important for identifying chloramine-related water quality problems.
- Calculate combined chlorine: Subtract free chlorine from total chlorine to determine the combined chlorine concentration.
- Understand acceptable levels: The CDC notes that many public health departments limit combined chlorine to 0.4 parts per million (ppm) or less. Operators should always follow their applicable state and local requirements.
- Correct elevated levels: When combined chlorine becomes excessive, trained operators should evaluate the cause and follow appropriate water treatment procedures. Breakpoint chlorination and supplemental treatment systems may be part of the solution.
3. Improve Ventilation and Air Circulation
Indoor swimming pool air quality requires more than controlling humidity.
- Bring in fresh air: Heating, ventilation, and air conditioning (HVAC) systems should provide adequate outdoor air to the swimming pool environment.
- Remove contaminated air: Systems should effectively exhaust air containing chloramines instead of continuously recirculating it.
- Pay attention to the water’s surface: Air movement near the pool is particularly important because chloramine-containing gases can accumulate close to swimmers.
- Don’t confuse dehumidification with ventilation: A system may effectively control moisture without supplying enough fresh air to manage chloramines.
This is especially important during colder months, when the temptation to reduce outside-air ventilation to save energy can create additional indoor air quality problems.
Facility managers should work with qualified HVAC professionals to evaluate airflow, ventilation rates, and system performance.
4. Reduce Contamination Before It Enters the Pool
Controlling chloramines starts with preventing the contaminants that contribute to their formation.
- Encourage pre-swim showers: Even a brief rinse can remove significant amounts of sweat, dirt, and other contaminants before swimmers enter the water.
- Promote good restroom habits: Encourage swimmers to use restroom facilities before swimming and remind patrons not to urinate in the pool.
- Educate employees: Lifeguards, swim instructors, coaches, and maintenance personnel should understand how swimmer behavior affects water quality.
- Post clear reminders: Simple signs and consistent communication can help establish better habits among patrons.
Preventing contamination reduces the amount of material that chlorine must react with, helping operators maintain better water and air quality.
5. Recognize Warning Signs and Respond
Pool operators should never accept strong chemical odors or persistent swimmer complaints as normal operating conditions.
Common warning signs include:
- Strong chlorine-like odors throughout the indoor pool area
- Burning or irritated eyes
- Persistent coughing or respiratory discomfort
- Elevated combined chlorine readings
- Complaints from employees who spend extended periods on the pool deck
When these issues arise, operators should investigate both water treatment and ventilation performance.
Chemical adjustments alone may not resolve an indoor air quality problem if the facility’s ventilation system is inadequate. Likewise, effective ventilation cannot compensate for poor water treatment.
The best approach addresses both systems together.
Read the Complete CDC Guidance
The CDC’s Chloramines and Pool Operation resource provides additional information on chloramine formation, swimmer hygiene, ventilation, water testing, and treatment strategies for commercial aquatic facilities.
Read the Official CDC Chloramines and Pool Operation Guidance
Important: CDC recommendations provide valuable public health guidance. Pool operators must continue to comply with applicable state and local swimming pool codes, regulations, and approved operating procedures.
For additional information about managing chloramines, see our article Indoor Pool? Stop That Smell!.
Need CPO Training for Your Team?
Understanding the relationship between water chemistry, chloramines, and indoor air quality is an important part of professional pool operation.
Aquatic Council provides live online and in-person PHTA Certified Pool Operator (CPO) training covering water chemistry, disinfection, circulation, filtration, equipment operation, and safe commercial pool management.