A hazard is something that can cause harm. Risk is the probability that a hazard will cause harm. A hazard assessment is simply a concerted effort to identify hazards present, assess the risks associated with those hazards, and select appropriate control measures to reduce those risks. A hazard assessment is an iterative process with no set end point. Hazard assessment should be revisited when any new hazards are identified either by observation, near miss, or accident and when the scope of work changes. Not revisiting the hazard assessment when the procedure or area initially assessed changes is a leading indicator for accidents.
There are several methods to perform a hazard assessment, but the first step is to identify the scope of the assessment. A single area or process will likely define the scope of the assessment. For example, when creating a Standard Operating Procedure, the scope of the hazard assessment is likely defined by the steps of the procedure to be performed and the area in which the procedure takes place.
The recommended method of hazard assessment is a Job Hazard Analysis (JHA). A JHA begins with a specific procedure to be performed. Each step is considered individually and hazards associated with each step are identified. After hazards are identified, risks associated with each hazard are assigned based on how likely the event is to occur and how harmful the hazard may be. Safety controls are then selected to reduce each risk, giving priority to the highest risks first.
For more information, examples, and templates to use in hazard assessments see the resources provided by the American Chemical Society.