The Definition of Machine Risk Assessment (ISO 12100)

Definition of Machine Risk Assessment

Machine risk assessment is the structured process of identifying hazards on a machine, estimating and evaluating the risk they create and deciding how to reduce that risk to an acceptable level.

ISO 12100 sets out the method most machine builders and safety engineers use. It works for any machine, from a single drill press to a full robotic line. A good assessment covers the whole life of the machine, not just normal production. Setup, cleaning, maintenance and troubleshooting are where many serious injuries happen.

Machine risk assessment matters to manufacturers, integrators, plant engineers, maintenance leaders and EHS managers. It is the basis for decisions about machine guarding, control system design and training. It is broader than a task-based job hazard analysis, which looks at the steps of a job. A machine risk assessment looks at the machine itself and everyone who interacts with it.

How Machine Risk Assessment Works

Risk Analysis

• Determine machine limits: define use limits (intended use and reasonably foreseeable misuse, users and their training), space limits (range of motion, access and clearance), time limits (service life and wear parts) and other limits such as materials and environment.
• Identify hazards: list hazards across all life-cycle phases, including transport, installation, operation, setup, cleaning, maintenance and decommissioning. Consider mechanical hazards plus electrical, thermal, noise, vibration, radiation, material and ergonomic hazards.
• Estimate risk: for each hazard, judge the severity of harm and the probability of that harm occurring.

Risk Estimation Elements

• Severity of harm: how bad the injury could be, from minor to fatal, and how many people could be affected.
• Frequency and duration of exposure: how often and how long people are in the hazard zone.
• Probability of the hazardous event: how likely the event is, based on reliability, history and human behavior.
• Possibility to avoid or limit harm: whether people can see it coming, react in time or get out of the way.

Risk Evaluation and the Three-Step Method

Risk evaluation decides whether risk reduction is needed. If it is, ISO 12100 uses a three-step method, applied in order:

• Step 1, inherently safe design: remove the hazard or reduce it through design, such as lower force, rounded edges or moving adjustments outside the hazard zone.
• Step 2, safeguarding and complementary protective measures: add guards, protective devices such as interlocks and light curtains, and complementary measures such as emergency stops.
• Step 3, information for use: provide warnings, signs, manuals and training for the risk that remains.

After each measure, the process repeats until the risk is adequately reduced and no new hazards have been introduced.

Regulations and Standards

ISO 12100:2010

ISO 12100:2010, "Safety of machinery, General principles for design, Risk assessment and risk reduction," is the basic type-A machinery safety standard. Other machinery standards build on it. ISO/TR 14121-2 gives practical guidance and worked examples of risk assessment methods. Results from the assessment feed the required Performance Level under ISO 13849 for each safety function.

ANSI B11.0

In the US, ANSI B11.0 (Safety of Machinery) sets out a similar risk assessment and risk reduction process. It ties risk reduction to the hierarchy of controls, from elimination through administrative controls and PPE.

OSHA

OSHA does not require a formal machine risk assessment by name. However, 29 CFR 1910.212 requires machine guarding to protect operators and other employees from hazards such as the point of operation, ingoing nip points, rotating parts, flying chips and sparks. A documented risk assessment is a practical way to show how guarding decisions were made. Maintenance tasks identified in the assessment also tie into lockout/tagout procedures under 29 CFR 1910.147.

European Union

Under the Machinery Directive 2006/42/EC, manufacturers must carry out a risk assessment before placing machinery on the market. The Machinery Regulation (EU) 2023/1230 replaces the directive from January 20, 2027, and keeps risk assessment as a core obligation.

Good Practices for Machine Risk Assessment

• Use a cross-functional team: include operators, maintenance technicians, engineers and safety staff. Operators know the shortcuts.
• Cover every task: assess setup, changeover, cleaning, jam clearing, troubleshooting and maintenance, not just production.
• Include foreseeable misuse: ask how people might reach in, climb on or bypass the machine, and design for it.
• Follow the three steps in order: do not jump to warning signs or training when a design change or guard is possible.
• Document assumptions: record limits, scoring method and reasons for each decision so others can review them.
• Review after changes: update the assessment after modifications, relocations, incidents or near misses.

Example of Machine Risk Assessment

A regional bakery bought a used dough sheeter and installed it with the original guards. Within weeks, a sanitation worker cut a finger while cleaning between the rollers with the machine jogging. The original assessment, done by the reseller, covered only normal production and did not consider cleaning.

The bakery repeated the risk assessment with operators and the sanitation crew. It added an interlocked cover with a low-speed hold-to-run mode for cleaning, wrote a lockout procedure for deep cleaning and updated training. The bakery now requires a full life-cycle risk assessment before any new or used machine goes into service.

Frequently Asked Questions: Machine Risk Assessment

What is ISO 12100?

ISO 12100 is the international type-A standard that sets general principles for machine design, risk assessment and risk reduction. Other machinery safety standards build on its method.

What is the three-step method in ISO 12100?

It is the order for reducing risk: first inherently safe design, then safeguarding and complementary protective measures, then information for use. Each step is applied before relying on the next.

Does OSHA require a machine risk assessment?

Not by name. OSHA requires effective machine guarding under 29 CFR 1910.212, and a risk assessment is a practical way to decide and document what guarding is needed.

How often should a machine risk assessment be updated?

Update it whenever the machine, its use or its location changes, and after any incident or near miss involving the machine. Many sites also review assessments on a set schedule.