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10.2 Use of Explosives
Explosives are used in construction and mining. Properly handled by experienced people they are very useful. Used by untrained workers they can cause fires and unwanted explosions.
| Term | Meaning |
|---|---|
| Blast area | The area where explosives are loaded and blasting is carried out. |
| Blasting agent | A mixture of fuel and oxidiser used for blasting that is not itself classed as an explosive. |
| Blasting cap | A metal tube, closed at one end, holding a charge of detonating compounds that can be set off by a safety fuse. |
| Electric blasting cap | A blasting cap designed to be set off by an electric current. |
| Detonating cord | A flexible cord filled with high explosive that can set off other explosives it touches. |
| Detonator | Blasting caps, electric blasting caps, and delay caps. |
Heat can raise the ambient temperature and so the risk of deflagration or detonation. Friction, impact, electricity, focused laser light and chemical incompatibility can start an explosive too, with effects from mild decomposition to detonation.
Transport
- Hire only licensed, physically fit drivers and check their knowledge of the local, state and federal rules on transporting explosives.
- Nobody may smoke, carry flame producing devices or carry firearms in or near a vehicle carrying explosives.
- Do not carry explosives or blasting agents together with other cargo, including blasting caps.
- The vehicle must be in good mechanical condition and strong enough for the load.
- Explosives travel in the maker's original containers or a Class II magazine, secured. Cover any exposed spark producing metal in the cargo area with wood or wool.
Storage
- Use special designated areas and approved magazines.
- Never store detonators, blasting caps, electric blasting caps or cartridges with other explosives or blasting agents.
- Do not smoke or use any fire producing device within 50 feet of a magazine.
- Do not store explosives underground unless there are at least two exits, and keep hoists, shafts and work areas at least 300 feet from underground storage.
- Keep magazines with detonators at least 50 feet from other explosives and blasting agents.
Initiating charges
- Do not use electric blasting caps where there is an external electrical source. Keep the leg wires short circuited, or shunted, until they are connected to the firing circuit.
- The blaster surveys the blast area to be sure that there is no stray current, and removes any extraneous current before the holes are loaded.
- All electric blasting caps in one blast must be of the same style and from the same manufacturer.
- Follow the maker's instructions or the contractor's guidelines for blasting and power circuits.
Firing the blast
- Clear the blast area of all people.
- Post warning signs where everyone can see them.
- Give a loud warning signal before firing.
- Check that no extra explosives are in the area and that people, equipment and vehicles are at safe distances.
- Station a flagger on nearby highways to warn traffic.
- The blaster fixes the time of the blast.
Misfires
After the blast the blaster inspects for misfires, makes sure that the area is cleared, warns everyone about the danger zone, and lets only qualified people enter it. Never try to pull explosives out of a misfired hole. Place a new primer in the hole and blast again. If that would be hazardous, the blaster may have the explosive washed out of the hole with water, or blown out with air if the hole is under water.
A study aid, not published or endorsed by IOSH or OSHA. Laws and limits differ between countries.