An ignition element (106) for heating temperature sensitive ignitable material (86) in an air bag inflator comprises an electrically conductive first material layer (142). An electrically conductive second material layer (144) has a portion (146) spaced from and overlying a portion (148) of the first material layer (142). A lossy dielectric material (180) is disposed between the overlying portions (146, 148) of the first and second material layers (142, 144). A high frequency alternating electric field is applied to the first and second material layers (142, 144). The temperature sensitive material (86) is located adjacent the ignition element (106). The temperature of the dielectric material (180) increases to a temperature sufficient to cause ignition of the temperature sensitive material (86) in response to the application of the high frequency alternating electric field to the dielectric material.

A method of blasting cap-sensitive, non-­nitroglycerine-sensitized explosives and an initiating assembly for use in the method are provided. The method comprises initiating a column of the explosives by directing two radial/forward shock forces from an initiator assembly substantially simultaneously along the column of the explosives towards each end of the column. The initiating assembly of the invention comprises at least two initiators assembled side-by-side so that their explosive ends are opposite. A moulded plastics holder (6) for holding two blasting caps (1, 8) in the required spatial relationship is also described.

A detonator (10) includes an elongate tubular member (12) which defines a longitudinally extending passage (14). At least one base charge (16 and 20) is located in the passage (14). A primary charge (18) is located in the passage 14 such that, upon initiation of the primary charge (18), a shock front generated by the primary charge (18) is propagated by the base charges (16, 18) in a plurality of directions. The base charge may be provided with an axial bore through which the flame front from the detonator initiator passes before detonating the primary charge.

A primer (10; 20) for explosives which comprises a shaped charge (12) of detonating material for use with initiating means which penetrates into the charge characterised in that said primer has a cavity (16) therein to receive said initiating means, and a shock attenuator (14) in the form of an insert (14) of inert material the density of which is less than that of the detonating material, the insert extending from the surface of the charge into the charge to a desired detonation region (34) and having a portion surrounding at least a part of the length of the cavity and defining an inlet (16.1, 16.3) for insertion of said initiating means, the density of the insert relative to the detonating material and shape thereof providing for improved detonation of the primer.