on the chlorine CYA chart the higher the cya the more chlorine it says needs to be reached .. as far as I knew only 2 ppm chlorine is a safe level .. going over 3 and up is hazardous .. what am I not understanding completely .. the efficiency of the chlorine? how can i test that in pool water? I;'ve been hold 5 plus chlorine for the last week .. two people have been in it no problems .. except for a light green pool