I have decided to write an article discussing repelling equipment. I will cover what is needed, and why. Firstly, helmets should be used to stop you from bumping your head, obviously. A light may be mounted on your helmet, to keep your hands free in unlit areas.
Gloves are needed to protect your hands from burning on the rope, or hitting your hands of the rock face, and also to assist with your grip. You will also need a pair of boots that have a lot of grip, to assist the hands in abseiling down a rock face. If you just let your hands do the work, you will tire very quickly. Your legs are you biggest and strongest muscles, so, use them! You can also wear knee pads and elbow pads to protect your knees and elbows when your crawling, or when you collide with the walls.
Ropes are obviously needed to make the descent, and a descender (or rappel device) will be needed. This is a friction device that allows you to make a decent in a controlled manner, and makes it as comfortable as possible for the user. You can get mechanical descenders, which are used by window washers, for example. However, for obvious reasons, this would be very unpractical, and would also be cheating! There would really be any point of doing it, if you used a mechanical descender.
A harness will also be necessary, and preferably a comfortable one, as some descents can take many hours, and would be awfully painful in the wrong harness. All in all, quite a bit of repelling equipment is needed. You can search these items, or purchase them by clicking on some of the links on this page.