The code comprises a head-code and seven sub-codes incorporated in one document, the sub-codes having the following titles: boilers and calorifiers; storage vessels; pipework, fittings, valves, taps and cocks; appliances (column radiators, surface panels, convectors); unit heaters; power driven circulating pumps for low pressure hot water heating installations; and thermal insulation. The head-code 341.300 deals with the general aspects of central heating by low pressure hot water, whilst the sub-code s cover in detail the subjects indicated in their titles. Each sub-code includes a list of the relevant British Standards.