What is the difference between HAZOP and HAZID?

HAZID (Hazard Identification) is a broader, earlier-stage review used to identify hazards at the concept or front-end engineering stage. HAZOP is a more detailed, node-by-node analysis applied at the detailed engineering stage when P&IDs (piping and instrumentation diagrams) are available.

GLOSSARY

HAZOP: Hazard and Operability Study — Definition, Process & When to Use It

HAZOP, or Hazard and Operability Study, is a structured risk assessment technique used to identify hazards and operability problems in process systems. A multidisciplinary team applies guidewords to process nodes, examines deviations from design intent, and documents consequences, safeguards, and actions.

Last updated 2026-05-01

What Is a HAZOP?

HAZOP definition: a qualitative risk identification technique in which a multidisciplinary team uses guidewords (MORE OF, LESS OF, NO FLOW, REVERSE, etc.) to systematically examine every part of a process design for potential deviations from the intended design intent — and then identifies the consequences and safeguards for each deviation.

HAZOP Guide Words

Guideword	Meaning	Example Deviation
NO / NOT	Complete negation of intention	No flow when flow is required
MORE OF	Quantitative increase	Higher pressure than designed
LESS OF	Quantitative decrease	Lower temperature than intended
AS WELL AS	Additional elements	Contamination in flow
PART OF	Only part of intention achieved	Missing component in mixture
REVERSE	Opposite of intention	Reverse flow in pipeline
OTHER THAN	Complete substitution	Wrong material in process

When Is a HAZOP Required?

Design of new process plants or significant modifications
OSHA Process Safety Management (PSM) covered facilities (29 CFR 1910.119)
COMAH (Control of Major Accident Hazards) regulated facilities in the UK/EU
Pre-startup safety reviews for new or modified equipment

Frequently asked questions

What is the difference between HAZOP and HAZID?: HAZID (Hazard Identification) is a broader, earlier-stage review used to identify hazards at the concept or front-end engineering stage. HAZOP is a more detailed, node-by-node analysis applied at the detailed engineering stage when P&IDs (piping and instrumentation diagrams) are available.

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