The terms risk and hazard are used often in the safety world, many times interchangeably. They have very different meanings, however, and when using these terms, care should be taken to use them appropriately. When evaluating a process or procedure, assigning these terms appropriately can help simplify the safety assessment process.

What is a hazard?

A hazard refers to a potential source of harm. Examples can include chemical, biological, radiological, and physical hazards. Toxic chemicals, infectious biologics, and moving mechanical parts are all different types of hazards. The hazard level of a particular item or condition is static, meaning it does not vary. However, it can be evaluated relative to other hazards. Simply put, a hazard is a material or condition that can have an adverse effect on a person’s health or physical property.

What is risk?

Risk is the potential for interaction with a hazard. Generally speaking, risk is referenced in relative quantitative terms as related to a specific hazard. For example, some situations are considered high risk, like walking on a sloped roof, while others are low risk, such as walking on a flat roof. In this case, falling off the roof is the hazard. Walking on a sloped roof carries greater risk of this occurrence than walking on a flat roof does.

When assessing safety programs, it is important to evaluate each hazard, and determine the risk associated with the specific use of that hazard. The same hazard can carry different levels of risk, depending on how it is used. Chemical hazards are a good example of this. If a scientist is using 5ml of methanol as part of an assay, that is a low risk compared to another scientist who wants to use 5 gallons of the same chemical. Because it can be quantitative, a line can be drawn that defines acceptable levels of risk for each associated hazard. The goal of the safety professional is to review the hazard information and evaluate the risk level to ensure each procedure does not exceed that line of risk tolerance.

One approach to these evaluations is to use a hazard risk assessment matrix. This is a simple tool to help determine if a particular procedure or process can be performed without excessive risk. For each evaluation, a value is assigned to the hazard level and another value to define the risk level, or the probability of a significant interaction with the associated hazard. Depending on the matrix being used, the numbers are then added or multiplied and compared to a predetermined range of numbers that delineate what work is acceptable, not acceptable, or needs further evaluation. This tool does not necessarily work for every scenario, and appropriate professional judgement is required for choosing the proper hazard and risk values. However, it is one way to evaluate a particular task in simplified terms.

This is the fourth blog in a ten-part Industrial Hygiene series that we are featuring monthly. We welcome your input on the series! For questions about hazard and risk analysis at your facility please email