Good afternnon NT, this is from The Fire Safety (Scotland) Regulations 2006, Part 1, 'Preliminary', Regulation 2(1)
"Dangerous Substance" means–
(a) a substance or preparation which meets the criteria in the approved classification and labelling guide for classification as a substance or preparation which is explosive, oxidising, extremely flammable, highly flammable or flammable, whether or not that substance or preparation is classified under the CHIP Regulations;
(b) a substance or preparation which because of its physico-chemical or chemical properties and the way it is used or is present in relevant premises creates a risk; and
(c) any dust, whether in the form of solid particles or fibrous materials or otherwise, which can form an explosive mixture with air or an explosive atmosphere;
"explosive atmosphere" means a mixture, under atmospheric conditions, of air and one or more dangerous substances in the form of gases, vapours, mists or dusts in which, after ignition has occurred, combustion spreads to the entire unburned mixture;
"hazard", in relation to a dangerous substance, means the physico-chemical or chemical property of that substance which has the potential to give rise to fire affecting the safety of a person, and references in these Regulations to "hazardous" are to be construed accordingly;
preparation" means a mixture or solution of two or more substances;
"safety data sheet" means a safety data sheet within the meaning of regulation 5 of the CHIP Regulations;
I am presuming that the NI version is similar.
However, Phil's anorak claim is a very accurate account where all the versions came from