Abstract: An intrinsically safe circuit for use in a hazardous environment includes a plurality of circuit sectors (1, 2) which are substantially isolated physically from one another by an electrical insulator, such as air, and are electrically connected, directly or indirectly, so as to define at lease one power transfer path (P1) between each circuit sector (1) and the other circuit sector (2) ; and power limiting means such as resistors (R1, R2) provided in each power transfer path between the connected circuit sectors for limiting the maximum power transfer value therebetween to a value less than a predetermined threshold value at which combustion in said hazardous environment is initiated.