4.—(1) Except in the case of a substance dangerous for supply which is listed in Part I of the approved supply list, where a substance or preparation is required to have more than one indication of danger in either of the following groups listed in decreasing order of severity—
(a)explosive, oxidizing, extremely flammable and highly flammable: or
(b)very toxic, toxic, corrosive, harmful and irritant,
only one of the indications of danger with its symbol from each group corresponding to the most severe indication of danger in that group need be shown.
(2) The risk phrases R12 (extremely flammable) and R11 (highly flammable) need not be used if they repeat the indication of danger shown on the label.