There are some devices, referred to as "initiating explosives"[9] , which transmit signals from one place to another using electrical or chemical (non-electric) energy, in order to obtain the detonation of explosive charges at a controlled time. Initiation sequences can be controlled by using electrical timing systems or chemical delay elements. Initiating explosives systems incorporate various explosive and inert components which may be wholly or partly consumed in the blast.

Non-electric initiation systems utilise chemical reactions, which can range from rapid burning to violent detonation, to initiate explosive charges either directly or via non-electric detonators. Electric initiation systems require a device which can generate or store electrical energy that is transmitted to electric detonators by a circuit of insulated conductors. A combination of electric and non-electric initiating explosives can be also used to initiate blasts. Non-electric systems cause little disruption to surroundings as they function and provide a high level of safety against accidental initiation by static electricity, stray electrical currents and radio frequency energy.

One of the key components in non-electric initiating systems is non-electric tubing - plastic tubing coated on the inside with a reactive powder. Non-electric tubing or signal tube is commonly attached at one end to a non-electric detonator to form a "detonating assembly". Signal tube has the particular advantage that it cannot be initiated by flame, friction or impact normally encountered in mining operations.

Another commonly used initiating explosive device utilised in blasting is the non-electric primer. A non-electric primer is formed when the non-electric detonator of a detonator assembly is located within a booster.

It is also known to use a cartridge of packaged explosives as a primer. Packaged explosives consist of a paper cylinder or plastic film tube which is filled with soft explosive composition. When used as a primer, a slit is made in the paper or plastic and a detonator inserted.


Primer is an initiation device which consists of a container, which holds the explosive, and a cap received on the open end of the container. The container has two lateral opposing cord tunnels which run the length of the container. The cord tunnels protect the fuse cord on the inside of the primer. The cap has two apertures which align with cord tunnels in the container. The cap has capwell for receiving the detonator. The capwell is pierceable so that a detonator can be inserted through the capwell and embedded directly in the explosive composition inside the container. In addition, the primer contains grooves in the bottom of the container and in the cap. The grooves communicate with the apertures and the recess in the cap and the cord tunnels to create a continuous conduit so that a fuse cord can be threaded therethrough to secure the cord to the primer and selectively position the primer in a borehole at the blast site.


A detonator is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the latter two being the most common.
The commercial use of explosives uses electrical detonators or the capped fuse which is a length of safety fuse to which an ordinary detonator has been crimped. Many detonators' primary explosive is a material called ASA compound. This compound is formed from lead azide, lead styphnate and aluminium and is pressed into place above the base charge, usually TNT or tetryl in military detonators and PETN in commercial detonators.
Other materials such as DDNP (diazo dinitro phenol) are also used as the primary charge to reduce the amount of lead emitted into the atmosphere by mining and quarrying operations. Old detonators used mercury fulminate as the primary, and it was often mixed with potassium chlorate to yield better performance.

Electrical detonators

There are three categories of electrical detonators: instantaneous electrical detonators (IED), short period delay detonators (SPD) and long period delay detonators (LPD). SPDs are measured in milliseconds and LPDs are measured in seconds.
In situations where nanosecond accuracy is required, specifically in the implosion charges in nuclear weapons, exploding-bridgewire detonators are employed. The initial shock wave is created by vaporizing a length of a thin wire by an electric discharge.
A new development is a slapper detonator, which uses thin plates accelerated by an electrically exploded wire or foil to deliver the initial shock. It is in use in some modern weapon systems. A variant of this concept is used in mining operations, when the foil is exploded by a laser pulse delivered to the foil by optical fiber.

Non-electric detonators

Non-electric detonators usually take the form of an ignition-based explosive. Whilst they are mainly used in commercial operations, non-electric detonators are still used in military operations. This form of detonator is most commonly initiated using safety fuse, and used in non time-critical detonations i.e. Conventional Munitions Disposal.


In an explosive, pyrotechnic device or military munition, a fuse (or fuze) is the part of the device that initiates function. In common usage, the word fuse is used indiscriminately. However, when being specific (and in particular in a military context), the term fuse describes a simple pyrotechnic detonating device, like the cord on a firecracker, whereas the term fuze is used to indicate a more sophisticated ignition device incorporating mechanical and/or electronic components e.g. a proximity fuze for an M107 artillery shell, magnetic/acoustic fuze on a sea mine, spring-loaded grenade fuze, pencil detonator or anti-handling device.

Modern day safety fuses are often used in mining and military operations, to provide a time-delay before ignition, and they more often than not are used to initiate an explosive detonator, thereby starting an explosive chain reaction to detonate a larger more stable main charge. Safety fuses are typically colored black (military) or fluorescent orange (commercial) to distinguish them from detonating cords such as Primacord, which are brightly colored or transparent. Fuses are found in fireworks, model cannons, matchlock firearms, some improvised explosive devices and many forms of pyrotechnics.

Burning fuses