You will need this licence if you intend to keep flammable liquids of Class 2 LPG, Class 3 and dangerous substances of Class 6 and 8.
Class 6.1 poison (toxic) substances are solids and liquids that present an immediate and serious hazard through ingestion, inhalation or skin absorption. Examples are agricultural chemicals (pesticides, herbicides), arsenic and its compounds and cyanide compounds.
Class 8 corrosive substances may be solid or liquid and will attack steel or aluminium or damage livery tissues (chemical burns on skin). Examples are sulphuric acid (battery acid), hydrochloric acid (spirits of salts for soldering) and sodium hydroxide (caustic soda, drain cleaner).