18. Any unintended collapse or partial collapse of—
(a)any building or structure (whether above or below ground) under construction, reconstruction, alteration or demolition which involves a fall of more than 5 tonnes of material;
(b)any floor or wall of any building (whether above or below ground) used as a place of work; or
(c)any false-work.
19. An explosion or fire occurring in any plant or premises which results in the stoppage of that plant or as the case may be the suspension of normal work in those premises for more than 24 hours, where the explosion or fire was due to the ignition of any material.
20.—(1) The sudden, uncontrolled release—
(a)inside a building—
(i)of 100 kilograms or more of a flammable liquid,
(ii)of 10 kilograms or more of a flammable liquid at a temperature above its normal boiling point, or
(iii)of 10 kilograms or more of a flammable gas; or
(b)in the open air, of 500 kilograms or more of any of the substances referred to in sub-paragraph (a) above.
(2) In this paragraph, “flammable liquid” and “flammable gas” mean respectively a liquid and a gas so classified in accordance with regulation 5(2), (3) or (5) of the Chemicals (Hazard Information and Packaging for Supply) Regulations 1994(1).
21. The accidental release or escape of any substance in a quantity sufficient to cause the death, major injury or any other damage to the health of any person.