[Callers] Wax, Dancer Safety and a Caller's Throat

Hi, We had a dancer injured at our last dance. A man fell and broke his hip. In perhaps 30 years of dancing I have never seen this before. Our hall is small. We had two sets in longways formation. To me it looked as if maybe a foot from one dancer in another line might have just touched his heel. I am not sure. He lost his balance. His feet may have slipped out from under him and he landed on the hip. I am wondering what to do to help prevent this in the future. I am especially interested in assessing the floor. How do you decide if it is too slippery? I know that there is a dance wax. Is it for making the floor more slippery or less? How do you know when to use it? Where do you get it? There was some confusion among some of the dancers at that part of the evening, which I was trying to fix, but it did not look as if this contributed to the accident. Have you had experience with dancer accidents while you were calling? What else besides possibly the wax, might help reduce what I always thought was a very small risk. I have been suffering some with what may be mild laryngitis. I had been practicing pretty regularly for an upcoming gig, but I did not feel that I was straining my voice. I have been drinking a lot of water. What else do you do - if anything - to help once you have throat or voice problems? I still have about 2 weeks before the gig. Thanks as always, Rickey