Shock (or signal) tubing is the basis of all non-electric initiation systems. Shock tubing consists of a 3 mm outer diameter plastic tube with a 1 mm hollow core. The core is lined with a coating of reactive powder (HMX and Aluminium) at around 16 grams per kilometre.

Shock tube can be reliably initiated by detonators or detonating cord but is succeptible to failure from shrapnel damage.

Fired shock tube above - note core is slightly blackened

Unfired shock tube above - note aluminium appears as a silvery coating

Shock tube is a robust and reliable product however liquid penetration of the core will cause failure. The common modes are:

• Oil penetration due to excessive sleep times in bulk explosives
• Water ingress through damaged sections. Damage is primarily caused by shrapnel from detonators, detonating cord or rock fragments projected across the blast.