217Obstruction in blast hole

217 Obstruction in blast hole (1) This section applies if an obstruction is met in a blast hole after charging has begun. (2) The person charging the hole may only remove the obstruction by— (a) a flow of water or water and compressed air; or (b) if a pressure water supply is not available—a flow of air applied through a length of safety tubing that has no ferrous metal fittings, and is advanced gently, without force, into the blast hole. (3) If the obstruction cannot be removed, the person charging the hole (a) add a primer cartridge to the charge; and

(b) continue charging above the obstruction until the stemming height is reached; and (c) after the charge is fired, search for any unexploded explosive. safety tube means a semiconductive plastic or rubber hose with an electrical resistance of— (a) no less than 15 000Ω per metre; and (b) no more than 2MΩ, measured along the length of the hose.