The use of chlorine in swimming pools has saved thousands of lives throughout history. Even though chlorine has its dangers, they are far outweighed by the good the chemical does in killing bacteria that are harmful to people using pools. Recently there has been a lot of publicity about the hazards of chlorine. Unfortunately chlorine gets the blame for the harm caused by chloramines.   
As an example, cars do not injure people, careless drivers injure people.  Chlorine, properly regulated in a pool, does not put people at risk.  Uninformed or careless pool operators put people at risk. The three main factors for safe pool water and good air quality are:

  • The chlorine level is kept between 1.5 and 2.5 with a pH between 7.3 and 7.5
  • No chloramines can be present in the pool water
  • The air circulation and dehumidification system must be functional and properly sized

If the air smells like chlorine, something is wrong. That acrid smell we sometimes associate with chlorine is usually an ammonia type compound.  In the swimming pool industry the cause of this odor is chloramines.  Chloramines (combined chlorine) occur when free chlorine combines with ammonia and other nitrogen compounds.  This combining process can be accelerated by perspiration, urine, saliva, body oils, lotions and some shampoos, soaps, fertilizers, and many industrial or household cleaners. 
The odor is created when water is not properly balanced. The odor intensifies when swimmers agitate the water, as in kicking or general warm-up swimming at a swim meet. The odor is worse at water level but can be extremely irritating at deck level or in the viewing area. Many times eye irritation and difficulty breathing accompany the odor. Sometimes the water may be hazy, but not always. Many times, the water will appear perfectly clear and the water test reads normal for free chlorine and pH. 
This has become such a widespread problem in indoor pools that people are hospitalized each year.  People with asthma are particularly at risk. Most of the problems occur in indoor pools. Outdoor pools have plenty of fresh air and sunshine (ultra violet light) so they are not as susceptible to the chloramines problem.
Chloramine formation can be accelerated by:

  • Swimmers not properly showering before entering pool.
  • Urination in the pool.
  • People doing a high level of aerobic activity and sweating in the water. (Note: everyone sweats when exercising in the water, the same as when they exercise on land.)
  • Residues from ammonia based cleaning products that are used on decks or in shower rooms and lavatories.
  • Residues from fertilizers used on landscaping (nitrogen based) that get tracked into building on shoes.
  • Poor air circulation and lack of fresh air introduction into the pool building.
  • Over use of “shocking” the pool for maintenance purposes.
  • Improper use of certain brands of chemicals not suitable for conditions specific to a geographic area.
  • Chloramines added to the municipal drinking water which is becoming common practice throughout the country.

What to do?
If chloramines are detected the most common solution is to shock the water.  This means super-chlorination (break-point chlorination) which raises the level of chlorine in the pool to 10 parts per million.  Normally dry chlorine powder or liquid chlorine is used to achieve super-chlorination. Recent studies show that many times this is not as effective as hyper-chlorination which is raising the level of chlorine to 20 parts per million.
These methods may temporarily burn out chloramines but will also necessitate the pool being closed for a few days. More than the normal amount of fresh air will also have to be introduced during this process.
Anecdotal evidence from people who have tried this solution seems to show that shocking the pool does not really help and can create a whole new set of problems.
Some success has been realized with a non-chlorine shock additive. Adding an oxidizer (potassium peroxy, monosulphate with brand names Oxykleer or Oxybrite) to the water converts the available chlorine to free chlorine.

If this process is done in the evening, swimmers can usually be in the pool the next morning. Fresh air introduction is still important. This is NOT a permanent solution.
Usually more than one thing needs to be changed to alleviate the problem.
The most common methods are:

  • Change the air circulation system to include more fresh air introduction and better turnover or a more efficient closed system of circulation and dehumidification. 
  •  Evaluate the type and brands of chemicals being used to treat the pool water for both chlorine and pH control.
  • Evaluate the pool filtration system to see if a filter that filters down to a more effective micron rating (like DE at 4 microns) would help.
  • Check the labels on all cleaning products to make sure they do not contain ammonia or are not nitrogen enriched.
  • Have your staff get the users of the pool to take showers before entering. This is usually required by state health codes but difficult to enforce.

Other preventive remedies:

  • Plan to install a medium pressure Ultra Violet (UV) water treatment system that cuts down on the amount of chlorine you have to use and also breaks down mono, di and tri chloramines.  UV kills bacteria which also gives an extra layer of protection for swimmers.
  • Consider installing an activated carbon filter on the fill pipe from the city for water that fills the pool.  This will help remove Chloramines from the source water.

We need to stop blaming chlorine for everything and start putting solutions into place. Bacteria in the water is extremely dangerous.  Chlorine has been the solution for generations.  Until a completely new method of water treatment is developed and field tested, it is still the best and safest method. 

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