I'm in the swimming pool a lot since I'm on the swim team and I have noticed that if I don't shower after getting out of the pool and drying off, the typical "chlorinated pool" smell will mostly go away. But, if I decide to shower later that night, the chlorine smell will come back very strong when my skin and hair gets wet again from the water in the shower. My swim team friends and I even found this same thing to happen just from licking your arm. Why does water seem to activate the smell?
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1$\begingroup$ The smell comes from chloramines, which are produced when chlorine reacts with nitrogen-containing organic compounds (which can be found, for example, in sweat). $\endgroup$– f''Commented Aug 2, 2016 at 4:27
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1$\begingroup$ Sodium hypochlorite is commonly used in swimming pools. Due it's hypo nature it is not fully stable and releases chlorine gas as it denatures, this would happen faster in solution . Some of the salt residue would dry on the skin and then solubilise again in the shower water later and you would be able to smell it. $\endgroup$– TechnetiumCommented Aug 2, 2016 at 6:54
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$\begingroup$ Also , 'pool chlorine' does smell when it's dry aswell ... $\endgroup$– TechnetiumCommented Aug 2, 2016 at 6:56
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1 Answer
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According to americanchemistry.com:
Pool smell is due, not to chlorine, but to chloramines, chemical compounds that build up in pool water when it is improperly treated.
Chloramines result from the combination of two ingredients: (a) chlorine disinfectants and (b) perspiration, oils and urine that enter pools on the bodies of swimmers. Chlorine disinfectants are added to pool water to destroy germs that can give swimmers diarrhea, ear aches and athlete's foot. Perspiration, oils and urine, however, are unwanted additions to pool water. By showering before entering the pool, and washing these substances from the skin, swimmers can help minimize pool smell. When chlorine disinfectants are added to water, two chemicals are unleashed that destroy waterborne germs: hypochlorous acid, $\ce{HOCl}$, and hypochlorite ion, $\ce{OCl-}$.
Some chemical reactions that then lead to the formation of chloramines include:
$$\ce{HOCl + NH3 -> NH2Cl + H2O}$$ $$\ce{HOCl + NH2Cl -> NHCl2 + H2O}$$ $$\ce{HOCl + NHCl2 -> NCl3 + H2O}$$
These are fairly volatile compounds, but can also, to different degrees, "stick" to your skin. When you take a hot shower, these are then liberated and you can smell it again.
