A portable area repellent device (10) comprising a housing, a source of heat (21) and a heating plate (12), with a mat (14) located above the heating plate (12) and a grill (16) located above the mat (14). The mat carries volatilizable material to be heated and dispensed to provide an insect repellent area. The housing comprises a vertically adjustable surface to adjust the size of a compartment accommodating mats of different sizes carrying said volatilizable material, the size of the adjustable compartment being manually controlled by a user.