The specific irritant that caused the problem, according to the article, was trichloramine (NCl3) which is the smelliest of the chloramines. The chloramine that is put into drinking water for disinfection is monochloramine (NH2Cl) and has much less of an odor and is much less hazardous. These chloramines collectively are what are measured as "Combined Chlorine" in your chlorine test kit (along with chlorinated organics) so these indoor pools were not regularly maintaining their pools properly and they probably had poor air circulation as well.

My guess is that they let the chlorine levels get too low relative to bather demand (i.e. they didn't keep the chlorine to ammonia ratio high). Also, for indoor pools it would be good to use a non-chlorine shock (monopersulfate, peroxymonopersulfate or MPS -- Dow trade name Oxone) to oxidize organics and ammonia before chlorine has a chance to produce chloramines. At least that's the theory. From what I've been told, indoor pools are a bear anyway you look at it.

Richard