How often should a risk assessment take place?

The Health and Safety Executive (HSE) says risk should be assessed "every time there are new machines, substances and procedures, which could lead to new hazards."  

An employer should carry out a risk assessment:  

• whenever a new job brings in significant new hazards. If there is high staff turnover, then the way new staff do their work should be checked against the risk assessment, and training provided in safe working practices if necessary; 
• whenever something happens to alert the employer to the presence of a hazard – for example, an unusual volume of sickness absence, complaints of stress and bullying, or unusually high staff turnover; 
• in response to particular changes to the level of risk to individual employees – for example, where an employee returns to work after a period of long-term sickness absence; or 
• Where an employee is pregnant or breastfeeding and their work might involve a risk to them or their unborn child’s health and safety. (Regulation 16, Management of Health and Safety at Work Regulations 1999).