NCN (acronym), see ‘nitro-carbon-nitrate’. near field, the distance from a point of interest in relation to a geometric quantity e.g. bore-

hole diameter or hydraulic radius of a drift or tunnel. The limit between far, intermediate and near field should be defined for each special use of the term. Some examples; for large diameter hole blasting on the surface, the region smaller ∼25 m from the source of the blast may be regarded as near field. In blasting underground, the near field ends at about two hydraulic diameters from the excavation drift or tunnel.