For an undertaking bound by a collective agreement, the employer and the employees' representatives may agree in writing to derogate from the provisions in section 12, first and second paragraphs, and section 13, second paragraph, if made necessary by objective or technical circumstances or circumstances related to the organisation of the work. Total daily working time must nevertheless not exceed 16 hours. The period for calculating an average in section 13, second paragraph, may not exceed 26 weeks.The provisions in these regulations may be derogated from for work that because of natural occurrences, accidental occurrences or other unforeseen events must be undertaken to avert a hazard or harm to life or property.Derogations under the first and second paragraphs are conditioned on the employees being assured compensatory rest periods, or, where this is not possible, suitable protection being arranged for the affected employees.