10. An employer shall ensure that—

(a) where it is possible for employees to open, close, adjust or secure windows skylights and ventilators—

(i) it may be done safely, and

(ii) when open, such windows, skylights and ventilators are not positioned so as to constitute a hazard to employees, and

(b) windows and skylights can be cleaned without risk to the safety, health or welfare of persons carrying out this work or of other persons present—

(i) by design,

(ii) by being fitted with devices, or

(iii) in conjunction with the use of equipment.