Terms originally from detonating cord firing describing both the surface hook up and the firing sequence
of the blast based on echelon by echelon firing with cord delays between the echelons as shown below:

A measure of the rate, in metres per second, at which the detonation wave travels through an explosive.

A category of facility that includes, but is not restricted to, the following:
(a) Multistorey buildings, eg. above 4 storeys.
(b) Large glass fronted buildings of high population.
(c) Health care facilities, childcare facilities, schools.
(d) Public buildings or structures of major historical value.
(e) Major traffic terminals, eg. railway stations, airports.
(f) Major public utilities, eg. gas, water, electricity works.