(a) In case of emergency involving danger to life, health or property or which requires immediate correction to continue the operation of a major industrial plant, or to assure the continuity of public utility service, excavation or demolition without explosives may be made without notice required by section 16-349 provided notice thereof is given as soon as reasonably possible.
(b) In case of an emergency involving an immediate and substantial danger of death or serious personal injury, explosives may be discharged if notice thereof is given at any time before discharge.