Amendment No. 3 to BS 7671 requires that within domestic premises, consumer units and similar switchgear must have non-combustible enclosures or be enclosed in a non-combustible cabinet. Domestic premises include single and multiple occupancy homes as well as places like guest houses where people sleep overnight. Non-combustible materials include steel. The enclosure must limit the spread of fire and includes the box and any components needed to maintain integrity. Similar switchgear performs the same fundamental function as a consumer unit. Cabinets may contain consumer units if the cabinet is made of non-combustible material.