Indoor pools certainly have air quality issues. Most notably: the infamous “chlorine smell” of the pool room itself. The first and most accepted method used to address this problem involves diluting the air with fresh air from outside of the contaminated area. In other cases, attempts are being made to install a return air vent at deck level to draw off the offending air particles.

Neither of these solutions actually addresses the root of the problem. Why does it exist at all? How can it be properly addressed with the least cost? These intriguing questions, when answered sufficiently, can turn around one of the most frustrating pool complaints.

Signs posted in locker rooms of both indoor and outdoor pools advise swimmers to shower before entering the pool. Most are unaware that this shower is more than a call to rinse obvious debris from the body. The more pertinent goal is to remove the chemical debris accumulated in various ways throughout the day. Lotions, oils, sweat, urine, feces, and natural body chemistry react with the chemicals used to treat the pool water.

The mixing of the various chemical components produces two specific reactions. Both reactions create significant health hazards for swimmers. The first by-product is called “chloramines”. This “sticky”, “heavy” substance generally lays on the surface top 4- 10” of the pool water. It is difficult to remove and contaminates all that it touches.

The second by-product is the unforgettable smell of the pool area.

Serious problems with conventional solution attempts

This is the off-gassing of the chemical reaction (chloramines) taking place between the pool chemicals and the foreign chemicals or contaminants being added.  As the concentration of by-products in the pool water increases, the off-gassing of these chloramines into the surrounding areas occurs.  Breathing air loaded with irritants can cause a variety of symptoms depending on the concentration of irritants in the air and amount of time the air is breathed.  Symptoms such as wheezing, sore throats, difficulty breathing, coughing, or aggravating asthma can occur and routine breathing may increase sensitivity to other types of irritants such as fungi and bacteria.

The solution of bringing more fresh air in from the outside of the building hosts it own set of problems. Primarily, it does not address the root of the problem. It therefore becomes a costly “bandage” to the situation at best. Increasing ventilation rates has proven both ineffective and expensive.   Particularly, these costs escalate dependent on the regional climate involved. The introduction of outside air of cold climates must be warmed before entering the pool environment. The hot, humid air of warmer climates is essentially untreatable. Pool dehumidification systems may potentially need to be upsized to handle the additional load.

For additional information review Chapter 5. Places of Assembly in the ASHRAE Handbook.

The concept of placing an air return duct at the deck level may hosts its own set of side effects. Hot, humid air rises. Its accumulation (stratification) at the ceiling level leaves the higher likelihood of moisture migrating into the ceiling areas. This could cause water damage, rot, mold and mildew growth. A deck level (return air) is incapable of dealing with this situation. It may also interfere with the negative pressure and relative humidly in the room. Overall, this is an inefficient and pricey answer to a problem that is left unresolved.

Summary and real solutions

The pool dehumidification system did not create, nor can it completely resolve, the problem of chloramines and poor pool chemistry which create the subsequent pool smell. A well designed dehumidifier and maintained air delivery system deals with the humidity control of the pool area and the problems created by undue humidity in the environment.

Don’t blame HVAC systems for bad air

The pool dehumidification may potentially aid the air turnover rates, but it cannot prevent the chemical reaction and accumulation of chloramines. The better answer is to educate swimmers of the necessity of showering prior to pool entry and to train/educate the staff maintaining the pool to control these reactions by maintaining the proper testing procedures and chemistry balance.

SO WHAT IS WRONG WITH THIS PICTURE?  This unit is less than one year old!

The corrosion and rust you see on the front and side of this unit is due to a consistent over - chlorination of the pool room and chemicals open/spilled in the mechanical room housing this system.  The equipment continued to have component failures and the pool room was shut down completely several times to “air out” the room of the “stink” of chloramine off-gassing of the pool over the next 24 months.

Combined chlorine levels in the water may be reduced by adding secondary disinfection systems, such as ultraviolet light or ozone. In addition, good hygiene is needed. Getting swimmers to shower before getting in the pool and promoting regular bathroom use to reduce the amount of urine in the pool will decrease the formation of irritants.