Alarm Rationalization Explained: ISA-18.2, EEMUA 191, and What Good Looks Like

Most alarm systems were not designed. They grew. A new piece of equipment was commissioned, a few alarms were configured, and nobody went back to question whether they were still necessary, correctly set, or useful to the operator receiving them. Repeat that process over ten or fifteen years and you end up with a system where the majority of alarms are either redundant, misconfigured, or actively unhelpful.

Alarm rationalization is the process of fixing that. This post explains what it involves, what the standards require, and what a well-rationalized alarm system actually looks like in practice.

What Is Alarm Rationalization?

Alarm rationalization is a formal review process in which every configured alarm in a control system is individually justified. For each alarm, the review asks: is this alarm necessary? Is it set correctly? Does it give the operator enough time and information to respond? Is it assigned the right priority?

Alarms that cannot be justified are modified or removed. Alarms that are misconfigured are corrected. The output is a master alarm database where every alarm has a documented purpose, a defined operator response, and a verified set point.

This is not a one-time cleanup. ANSI/ISA-18.2 treats alarm rationalization as a mandatory, ongoing work process within a full alarm management lifecycle. It is not complete until it covers every alarm in the system, and it requires periodic review as the process and equipment change over time.

What the Standards Say

Two documents define the benchmark for acceptable alarm system performance: ANSI/ISA-18.2-2016, the North American standard for alarm management in the process industries, and EEMUA Publication 191, the globally recognised guideline for alarm system design and management. IEC 62682 aligns closely with both. All three were updated within the past few years and are now harmonised in their core requirements.

Their shared benchmark is straightforward. A well-managed alarm system should present no more than one alarm per operator per ten minutes during normal operations; roughly 150 alarms per operator per day. During a major plant upset, no more than ten alarms should present in the first ten minutes (EEMUA 191, 4th Edition, November 2024).

In practice, most unrationalised facilities exceed these targets by an order of magnitude. The gap between the benchmark and reality is not a measurement artefact. It is what happens when alarm systems are never systematically reviewed.

The Bad Actor Problem

Alarm rationalization sounds like it requires reviewing thousands of alarms, which puts many facilities off starting. In practice, the distribution of alarm activity is highly skewed.

The top ten alarms in a typical unrationalised system account for 60 to 80 percent of all alarm occurrences (Hexagon/PAS). Resolving those bad actors alone, through set point adjustment, alarm suppression logic, or removal, can reduce overall alarm rates by 60 to 80 percent. In one documented case, just seven alarms accounted for 98 percent of total alarm load.

This means the most impactful phase of an alarm rationalization programme is often achievable in days or weeks of targeted analysis, not months of exhaustive review. Starting with bad actor identification gives operations teams a fast, measurable win that builds momentum for the broader rationalisation effort.

What Alarm Rationalization Actually Involves

A full alarm rationalization programme covers several connected activities.

Alarm philosophy.  Before reviewing individual alarms, the facility needs a written alarm philosophy that defines what constitutes a valid alarm, how alarms should be prioritised, and what is expected of operators in response. ISA-18.2 treats this as a prerequisite for rationalization.

Baseline and bad actor analysis.  Alarm performance data is collected and analysed to identify the highest-frequency alarms. These bad actors are the first priority for rationalization.

Documentation and rationalization.  Each alarm is reviewed against the alarm philosophy. The review documents the alarm’s purpose, cause, consequence, operator response, and priority. Alarms that cannot pass this review are modified or removed.

Ongoing audit and management of change.  A rationalized alarm system degrades without discipline. Every change to the control system that affects alarms requires review. Alarm performance monitoring should be continuous, not periodic.

Rationalization Addresses Detection. Notification Is a Separate Problem.

This is the point that most alarm management programmes miss entirely.

Alarm rationalization addresses whether the right alarms are configured and set correctly. It does not address what happens after a valid alarm fires. Getting the alarm to the right person, on the right device, within the right timeframe is a separate capability; and one that ISA-18.2, EEMUA 191, and IEC 62682 have no published benchmarks for.

A fully rationalized alarm system that relies on an operator in the control room to pick up a phone and call the right person has solved half the problem. If that call goes unanswered, or if the operator is managing an upset and cannot make the call, the alarm notification has failed regardless of how well the alarm was configured.

This is the gap that SeQent’s FirstPAGE Alarm Manager (FPAM) addresses. Once a valid alarm fires, FPAM routes it automatically to the right person on the right device, two-way radio, smartphone, PA system, or Andon display, with automatic escalation if the first responder does not acknowledge within a defined window. The alarm rationalization work determines which alarms matter. FPAM ensures those alarms reach someone accountable every time.

Want to see how SeQent Alarm Management handles alarm notification and escalation in a manufacturing environment? Get in touch!

Sources

• EEMUA. Publication 191, 4th Edition. November 2024. https://www.eemua.org/products/publications/print/eemua-publication-191

• ISA. ANSI/ISA-18.2-2016: Management of Alarm Systems for the Process Industries. https://www.isa.org/products/ansi-isa-18-2-2016-management-of-alarm-systems-for

• Hexagon/PAS. The Most Important Alarm Improvement Technique in Existence. https://aliresources.hexagon.com/operations-maintenance/the-most-important-alarm-improvement-technique-in-existence

• ProcessVue. The Sense and Nonsense of Alarm System Performance KPIs. https://www.processvue.com/downloads/Alarm_system_performance_KPIs_V1_0.pdf