The common advice is that the amount added must raise the level of chlorine to 10X the level (in parts per million) of chloramines present in the pool water; this is "shocking".
[citation needed] Although a verb for superchlorination,[3] "shock" is often misunderstood (through marketing and sales language) to be a unique type of product.
While "shocking" pools to reduce the buildup of chloramines works with inorganic, ammonia-based chloramines, in two studies it was found ineffective with the organic chloramines present in all pool water e.g. with creatinine, an organic component in human sweat.
Indeed, superchlorination produces free chlorine that reacts with organic contaminants to form a variety of disinfection byproducts (DBPs) which are hazardous to swimmer health e.g. one of the worst DBPs is the noxious and volatile trichloramine (NCl3), well known for irritating the eyes nearby a pool.
It has been pointed out that ozone is an excellent alternative, a much more effective oxidizer than chlorine shock.