An occupational health risk assessment is simply a careful examination of what could cause harm in the workplace, so that you can decide whether you have taken enough precautions or need to do more to prevent occupational illnesses.
You are legally required to assess the health risks in your workplace. The important things you need to decide are whether a health hazard is significant, and whether you have it sufficiently covered by precautionary measures so that the risk is small.
STEP 1: Look for the hazards.
How Dangerous is the Hazard?