The thesis is associated with the evaluation and development of micro climates to enable satisfactory work tasks to be undertaken in environments hostile to man's normal physiological regulation. The areas of elevated temperature and high voltage electric fields, with particular reference to inspection and work tasks in pressure vessels associated with nuclear power reactors and 'live line' maintenance on electricity transmission lines being the main objectives, based on the economic problems caused by the outage of modern electrical generating and transmission plant. [Continues.]