This clause of Part 1 is replaced by the following. This part of IEC 60335 deals with the safety of flexible sheet heating elements intended to be incorporated into floors and walls below 1,2 m and above 2,3 m and in ceilings, their rated voltage being not more than 250 V for single-phase installations and 480 V for other installations. Flexible sheet heating elements are converted into heating units that are incorporated in the building in accordance with the instructions after which the required level of protection against hazards is achieved. NOTE 101 Attention is drawn to the fact that in many countries, different wiring rules apply; for heating units intended to be used in vehicles or on board ships or aircraft, additional requirements can be necessary; in many countries, additional requirements are specified by the national authorities for fire protection, the national authorities for building regulations, the national health authorities, the national authorities responsible for the protection of labour and similar authorities. NOTE 102 This standard does not apply to heating units intended exclusively for industrial purposes; heating units intended to be used in locations where special conditions prevail, such as the presence of a corrosive or explosive atmosphere (dust, vapour or gas); blankets, pads, clothing and similar flexible heating appliances (IEC 60335-2-17); foot warmers and heating mats (IEC 60335-2-81); heated carpets and for heating units for room heating installed under removable floor coverings (IEC 60335-2-106); flexible sheet heating elements incorporated in other appliances.