We regret to inform you that the smell which you call "chlorine" at the swimming pool is not, in fact, just the cleaning agent chlorine. In fact, if it smells too strongly of "chlorine" it might be a good idea to get out of the pool entirely, for it is the result of something called "chloramines".
Chlorine doesn't actually give off the distinctive "pool smell", although chlorinated water can have a slight chemical odor that can be smelled in pools without good ventilation. Chloramines, on the other hand, do, and are produced when chlorine reacts with ammonia from the sweat, body oils and urine of pool users.
One, two, or three of ammonia's hydrogen ions are replaced with chlorine, forming monochloramine, dichloramine and, you guessed it, trichloramine. While the first is sometimes added to pools as a disinfectant, the second two are what you have been calling the "chlorine smell", according to the American Chemistry Council.
In fact, the more the pool smells, the less free chlorine there is in the pool, meaning it's time to add more chlorine to disinfect it.
"It is good advice," the Water Quality & Health Council explains, "to stay out of the water when a strong chemical smell pervades the air around any type of pool, indoor or outdoor."
"It is true that the more urine there is to combine with chlorine, the higher the level of unwanted, smelly chloramines in the pool," the Water Quality & Health Council continues. "Following that thread, if chlorine is combining chemically with contaminants like urine, then it is not available to destroy germs in the pool that can make swimmers sick with diarrhea, swimmer’s ear and various skin infections."
So how much sweat, pee, and oil are we all leaking into pools? It's not easy to estimate sweat and oil, but one team of chemists from the University of Alberta has had a good go at pee.
By measuring artificial sweeteners which pass through you and into your pee, the team was able to estimate that in a typical 832,700 liter (220,000 gallon) commercial-size swimming pool, about 75.7 liters (20 gallons) of that is pee. In a typical home pool, assuming your family has the same willingness to pee in their own pool as they do in public pools, that's around 7.6 liters (2 gallons) of pee you're swimming in. No wonder it smells so strongly of "chlorine".