Hot tools
Straighteners run up to 230°C, and a hot iron looks exactly like a cold one. It heats in a minute and takes far longer to cool, so most of the risk is after you've finished with it. Wax is the other half of this row, and it fails differently: it goes onto skin at temperature, so the check has to happen before every client, not once when the pot went on.
This is one hazard. Your register is the set that applies to you — under 20 questions, about five minutes, free.