Where a night worker’s job involves special hazards or heavy physical or mental strain, no averaging of hours is allowed. Instead, the employer must ensure that the worker does not exceed eight hours’ work in any 24-hour period that includes night work (regulation 6(7), WTR). This includes work that a risk assessment carried out under the Management of Health and Safety at Work Regulations 1999 (see Chapter 3) shows to involve a significant risk.