straight forward health and safty advice 
Any work that is unfamiliar should be regarded as potentially of high risk Carrying out a comprehensive Risk Assessment will show if the task is within your capabilities and resources. If there is any doubt, seek professional advice about the work. Do not allow anybody to undertake any work that may be a risk to themselves, or to others, until they have been trained and have satisfied a competent person of their ability to perform the work safely and efficiently. Some work is obviously of a much higher risk. For example, work that is carried out at high level, or on a roof, is usually considered to be a high risk activity where special precautions are needed. Likewise, working in a confined space requires special attention.  A confined space can be any space that is enclosed, where there is a risk of death or serious injury from hazardous substances or dangerous conditions, e.g. lack of oxygen, poisoning, explosion or fire.
The handling and storing of certain types of chemicals may also present a high risk to the person doing the task and may cause damage to the environment if spilt.
Some confined spaces are easy to identify, e.g. enclosures with limited openings: storage tanks; silos; reaction vessels; enclosed drains; sewers
Others are less obvious, but can be equally dangerous, for example: open-topped chambers; vats; combustion chambers in furnaces, etc; ductwork; unventilated or poorly ventilated rooms.
General safety