The Planning (Hazardous Substances) Regulations (Northern Ireland) 2015

3.  In categories 6, 7, 8 and 9 “flammable”, “highly flammable” and “extremely flammable” mean—

(a) flammable liquids: means substances and preparations having a flash point equal to or greater than 21°C and less than or equal to 55°C (risk phrase R 10), supporting combustion;

(b) highly flammable liquid means—

(i) substances and preparations which may become hot and finally catch fire in contact with air at ambient temperature without any input or energy (risk phrase R 17); and

(ii) substances and preparations which have a flash point lower than 55°C and which remain liquid under pressure, where particular processing conditions, such as high pressure or high temperature, may create major-accident hazards;

(iii) substances and preparations having a flash point lower than 21°C and which are not extremely flammable (risk phrase R11, second indent);

(c) extremely flammable gases and liquids means—

(i) liquid substances and preparations which have a flash point lower than 0°C and the boiling point (or, in the case of a boiling range, the initial boiling point) of which at normal pressure is less than or equal to 35°C (risk phrase R12, first indent); and

(ii) gases which are flammable in contact with air at ambient temperature and pressure (risk phrase R12, second indent), which are in a gaseous or supercritical state; and

(iii) flammable and highly flammable liquid substances and preparations maintained at a temperature above their boiling point.