all fire condition firing setback acceleration in the direction of the arrow 21 acting over relatively long firing time is achieved but provides enough resistance to prevent ignition under no fire conditions acceleration profiles with lower than total all fire impulse levels as is shown in fig1 the diameters of the top cap 12 and the base plate 13 are larger than the outside diameter of the bellow 14 this allows the insertion of a safety member such as a safety pin in a gap formed between the top cap 12 and the base plate 13 to keep them apart thus preventing accidental ignition during transportation of munitions or accidental dropping and the like the overall view of the inertial igniter as assembled with a typical thermal battery together with the safety pin 21 in its engaged and disengaged positions are shown in fig2 and 3 respectively as can be seen in fig2 when the safety pin 21 is engaged i e when it is positioned between the top cap 12 and the base plate 13 as shown in fig2 the top cap 12 is prevented from moving towards the base plate 13 thereby preventing igniter activation the safety pin 21 can be provided with a positive lock in its engaged position for example the safety pin u201c fork u201d 23 fig3 is larger than half the circumference of the bellow 14 and is flexible and preloaded to require certain amount of force in the direction of the arrow 24 to disengage it from the inertial igniter 10 this provision is made for the sake of safety and to prevent accidental pulling disengagement of the safety pin 21 in certain applications the safety pin 21 may.