A chainsaw is a powerful tool designed to be used with due care. With a commanding engine and some strong, forceful metal chains, a chainsaw can cause major injuries if it gets into the hands of someone with an inadequate amount of knowledge on how to use it properly. Work associated with using the tool is often dangerous with a high risk of injury.
It is against the law for chainsaw operators to carry out work without having received relevant training. Just as importantly, however, chainsaw workers must wear the appropriate PPE as laid out by HSE.