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bromine or chlorine? MPS would hint to bromine, but just want to make sure.Also, what color is the ring/stain?MPS will release gas <Clip> Shocking after use rather than before and ventilating well for a couple minutes <clip>Does the room smell "chlorininy"?
I had the coughing problem for a while on an outdoor spa, believe it or not. <clip>I've since switched to an ozonator, Nature 2 cartridge and SpaGuard Enhanced Shock and have not had the coughing problem nor the ring around the tub since. The only thing I can attribute it to is my sensitivity to the Soft Soak. <clip> you may want to consider switching sanitizers and see if that helps. Good luck!-Sarge
It may have nothing to do with your chemicals. I don't know what kind of ventilation you have for your indoor location, but check carefully around the outside of the tub and in the area around it for any signs of mold. That sort of thing can cause coughing and a whole lot of other real bad things. Good luck...I hope you find your problem.
If you are not using a saznitzer like chlorine or bromine or a biguanide system, you need to strat. Not using a residual sanitizer can be very dangerous for your health.Without using a sanitizer like the ones mentioned above, you could have had bacteria growing in your tub for the last 6-8 months.