171. An employer shall—

(a) for the purpose of preventing and providing protection against explosions, take technical and organisational measures that are appropriate to the nature of the operation and in order of priority ensure that those measures—

(i) either

(I) prevent the formation of explosive atmospheres, or

(II) where the nature of the activity does not allow that, avoid the ignition of explosive atmospheres including by electrostatic discharges where persons at work or the working environment act as charge carrier or charge producer, and

(ii) mitigate the detrimental effects of an explosion so as to ensure the health and safety of persons at work,

(b) where necessary, combine and supplement the measures referred to in paragraph (a with measures against the propagation of explosion,

(c) review the foregoing measures regularly and whenever significant changes occur,

(d) take the necessary measures, in compliance with Regulation 169, to ensure that—

(i) where explosive atmospheres may or are likely to arise in such quantities as to endanger the safety and health of persons at work, or of others, the working environment is such that work can be performed safely,

(ii) in working environments where explosive atmospheres may arise in such quantities as to endanger the safety and health of employees—

(I) there is appropriate supervision of employees, and

(II) that supervision includes the appropriate technical measures,

(iii) any escape or any release, or both, whether intentional or not, of flammable gases, vapours, mists or combustible dusts which may give rise to explosion hazards are suitably diverted or removed to a safe place or, if that is not practicable, safely contained or rendered safe by some other suitable method and

(iv) if an explosive atmosphere contains several types of flammable or combustible gases, vapours, mist or dusts, or any combination of them protective measures are appropriate to the greatest potential risk.