VH Technical Authority/Trainer Steve Tilling has written an excellent article regarding PPE Requirements for Working at Height.
This is a great read for those that "need to brush up on their PPE Management Systems, or are confused by what is actually required. It is split into 4 parts covering the LAW in part one, the Best Practice Guidelines in Part 2 and the ASNZS Standards in Part 3. Part 4 is a bonus part on how a Professional might set up a system".