Alarms & Alarm Management Glossary
Alarm setpoints, deadbands, annunciation, rationalization, flooding, shelving, and on/off delays. 100 terms in this topic - each defined in plain English on its own page.
An alarm is only useful if it reaches the right person, means something, and demands an action. This topic covers the discipline of alarm management: how alarms are configured (setpoints, deadbands, delays), how they are presented and acknowledged, and how alarm systems degrade (nuisance alarms, chattering, floods) and get rationalized back to health. The vocabulary follows the lifecycle thinking of ISA-18.2 and EEMUA 191 without reproducing either standard.
100 Terms
What is an acceptable alarm rate per operator?
Benchmark rates for standing, average, and peak alarms that keep one operator able to keep up.
Read → GlossaryWhat Is Alarm Acknowledgment?
The operator action of ack'ing an alarm, plus the active/normal and acked/unacked state model.
Read → GlossaryHow are vibration alarm and trip levels set?
Choosing Alert and Danger setpoints from ISO zones and baseline, with voting and delays to avoid nuisance trips.
Read → GlossaryWhat Is an HMI Alarm Banner?
The persistent strip on every screen that surfaces the top unacknowledged alarms so none are missed.
Read → GlossaryWhat is an alarm beacon or strobe?
Visual alarm device that flashes for alarms in high noise, rated in candela and colour-coded by alarm type, driven by F&G logic.
Read → GlossaryWhat Is an Alarm Deadband?
The gap between an alarm's trip and reset points that stops chatter, sized to the signal's noise.
Read → GlossaryWhat Is Alarm Escalation?
Tiered routing of an unacknowledged alarm to on-call staff by SMS, email, and voice for unmanned sites.
Read → GlossaryAlarm Flood
A burst of alarms that overwhelms an operator - ISA-18.2's 10-in-10-minutes threshold, its causes, and how to prevent it.
Read → GlossaryHow is alarm flood rate measured?
The ten-in-ten-minute threshold that defines a flood, distinct from average rate, reported as time in flood.
Read → GlossaryWhat Causes an Alarm Flood and How Do You Find the Trigger?
How one trip cascades through interlocks or comms loss alarms every point, and how first-out and sequence-of-events reconstruction finds the root.
Read → GlossaryWhat Is Alarm Flood Suppression?
First-out logic, cause-based suppression, and grouping that cut the flood an operator sees during a trip.
Read → GlossaryWhat is alarm grouping?
Consolidating related points into one logical alarm by unit, cause, or geography so an event annunciates once.
Read → GlossaryWhat Are Alarm Management KPIs?
Average and peak alarm rate, time in flood, standing alarms, and the ISA-18.2 and EEMUA target values.
Read → GlossaryWhat Are Alarm On-Delay and Off-Delay?
Time delays that stop chattering and transient alarms by requiring a condition to persist first.
Read → GlossaryWhat is alarm persistence time?
The minimum duration a condition must stay true before the alarm annunciates, filtering momentary spikes that need no action.
Read → GlossaryWhat Is an Alarm Philosophy Document?
The governing rulebook defining priority, HMI, and rationalization rules as ISA-18.2 lifecycle stage one.
Read → GlossaryWhat Is Alarm Priority?
The ranking set by consequence and response time that tells operators which alarm to handle first.
Read → GlossaryWhat is alarm priority color coding?
Reserving specific colors and cues for alarm priorities so operators read severity at a glance, unused by normal graphics.
Read → GlossaryWhat is an alarm priority scheme?
The documented ABC framework that assigns every alarm a consistent priority from consequence and response time.
Read → GlossaryAlarm Rationalization
The ISA-18.2 review that decides which alarms are justified, what they mean, and how urgent each one really is.
Read → GlossaryWhat Are Alarm Setpoint and Limit Types?
The tiered LL, L, H, HH limits and how each level maps to escalating operator response.
Read → GlossaryAlarm Shelving
The controlled, time-limited way an operator silences a known nuisance alarm - with automatic re-activation so nothing stays hidden.
Read → GlossaryWhat is an alarm sounder?
Audible notification device rated in dB(A) above ambient noise, with selectable tones and coverage spacing, wired to a supervised circuit.
Read → GlossaryWhat Is an Alarm Summary?
The live list of active alarms operators sort, prioritize, and acknowledge.
Read → GlossaryWhat Is Alarm Suppression?
Automatic, logic-driven hiding of alarms irrelevant to the current plant state, distinct from shelving.
Read → GlossaryWhat Is an Alarm System Audit?
The periodic ISA-18.2 review that benchmarks alarm performance against KPI targets and drives improvement.
Read → GlossaryWhat is an alarm annunciation sequence?
The ISA-18.1 style states a point moves through: flash, horn, acknowledge-to-steady, ringback, and reset.
Read → GlossaryWhat is a band alarm?
An alarm that trips when a value leaves a window bounded by both an upper and lower limit, for variables bad in either direction.
Read → GlossaryBenchmark an Alarm System
Sample a period with a real upset, compute the baseline metrics, and rank the bad actors into a target list.
Read → GlossaryBuild a Priority Matrix
Set the levels, define the consequence and response-time axes, and calibrate the cells to a bottom-weighted distribution.
Read → GlossaryHow do you build an alarm shelving policy?
Name who may shelve, cap the duration with auto-return, require a reason, exclude safety alarms, and audit every shelve.
Read → GlossaryBuild an Escalation Matrix
Map priority to contacts, define timing and the escalation path, pick channels, and build a backstop that cannot dead-end.
Read → GlossaryCalculate Alarm Rate
Draw the console boundary, count annunciations correctly, pick a fixed window, and report average and peak separately.
Read → GlossaryWhat is a calculated alarm?
An alarm triggered by an expression over several tags, like high flow with low pressure, only as good as its worst input.
Read → GlossaryWhat Is a Chattering Alarm?
An alarm that rapidly cycles active and clear near its setpoint, cured by deadband and delays.
Read → GlossaryWhat Is Collection Deadband Versus Alarm Deadband?
One controls when a historian stores a sample, the other prevents alarm chatter, both tuned in percent of span.
Read → GlossaryCommission Alarm Suppression
Define states and their detection, map suppressions with justification, and test every transition, especially the return.
Read → GlossaryWhat is a companion alarm?
A known downstream effect of another alarm, suppressed via defined cause-consequence pairs so operators see the root cause.
Read → GlossaryConduct an Alarm System Audit
Reconcile live config against the database, verify KPIs, confirm change control held, and record findings with actions.
Read → GlossaryHow do you configure a rate-of-change alarm?
Pick the window for the move's timescale, set the rate limit above the fastest normal move, and filter the input against noise.
Read → GlossaryWhat does CRM alarm management require?
A written, maintained alarm plan with performance review, and the SCADA practices that keep alarms meaningful to the controller.
Read → GlossaryDesign State-Based Suppression
Model only the states that matter, source a reliable state signal, and set per-state rules that never hide a live hazard.
Read → GlossaryWhat is the difference between a deviation alarm and an absolute alarm?
Deviation trips on error from a moving setpoint; absolute trips on a fixed value. A guide to which to use and how each misleads.
Read → GlossaryHow do you diagnose nuisance breaker trips in a control panel?
Identify which protective element operates and when: inrush at power restore, moisture leakage, heating terminations, or honest overload - measured, not guessed.
Read → GlossaryWhat Is EEMUA 191?
The UK alarm management guideline that set benchmark alarm rates like one alarm per ten minutes.
Read → GlossaryWhat is an email alarm notification?
An alarm sent to a mailbox by SMTP, fine for low-priority alerts but unreliable for time-critical ones.
Read → GlossaryWhat is an escalation matrix for alarm notifications?
The grid of severity and time-unacknowledged that maps who is contacted at each tier, designed so critical alarms never dead-end.
Read → GlossaryEstablish an Alarm Philosophy
Define what an alarm is, set the priority rules and KPI targets, settle the handling rules, and get it formally approved.
Read → GlossaryFirst-Out Alarm
The logic that flags which alarm tripped first in a shutdown cascade, so operators find the root cause instead of the symptoms.
Read → GlossaryWhat Is a First-Out Annunciator?
The alarm panel whose first-out logic flags the initiating trip alarm.
Read → GlossaryWhat are the alarm setpoints on a combustible gas detector?
The two-stage %LEL scheme: a low alarm near 20% LEL and a high alarm near 60% LEL, both below the explosive limit.
Read → GlossaryWhat is a general alarm?
Site-wide emergency signal telling everyone to stop and respond, sitting above gas and prepare-to-abandon in the tone hierarchy.
Read → GlossaryIEC 62682 vs ISA-18.2: how they relate
Why the international alarm standard tracks ISA-18.2 so closely, how aligned they are, and which one to cite for a given project.
Read → GlossaryWhat is a high wet well overflow alarm?
The critical high-high alarm that warns of an imminent sewer overflow and triggers an operator callout.
Read → GlossaryWhat Is an Independent High-Level Alarm?
The overfill alarm that uses its own sensor, wiring, and logic separate from the tank gauging transmitter.
Read → GlossaryInvestigate an Alarm Flood
Reconstruct the sequence, find the first-out and initiating event, separate consequential alarms, and prevent recurrence.
Read → GlossaryWhat Is ISA-18.2?
The alarm management standard defining a lifecycle from philosophy through audit, aligned with IEC 62682.
Read → GlossaryWhat are the stages of the ISA-18.2 alarm lifecycle?
Philosophy, identification, rationalization, design, implementation, operation, maintenance, monitoring, change, and audit, in order.
Read → GlossaryWho is responsible for the ISA-18.2 alarm system?
How ownership splits across a philosophy owner, a rationalization team, control engineers, operators, and an independent auditor.
Read → GlossaryISA-18.2 vs EEMUA 191: which do you follow?
A standard versus a guideline: how their status and structure differ, and why most alarm programs use both together.
Read → GlossaryWhat Is a Latched Alarm?
An alarm that stays annunciated after the condition clears until reset - latching vs non-latching for trips.
Read → GlossaryWhat Is a Master Alarm Database?
The D&R record of every alarm's setpoint, cause, consequence, and required operator action.
Read → GlossaryWhat is mode-based alarm suppression?
Automatically hides alarms expected in the current mode, like startup or shutdown, so operators avoid nuisance floods.
Read → GlossaryWhat Is NFPA 72?
The National Fire Alarm and Signaling Code: initiating devices, notification, integrity monitoring, and F&G-to-ESD interface.
Read → GlossaryWhat is alarm notification deduplication?
Suppressing repeat notifications for the same recurring condition so one event does not send dozens of messages.
Read → GlossaryWhat is an alarm notification digest?
A periodic summary that batches low-priority alarms instead of sending one message per event.
Read → GlossaryNuisance Alarm
The chattering, fleeting, and stale alarms that clutter a screen without any real action - and the deadband and delay fixes for them.
Read → GlossaryWhat Is an Off-Delay Timer (TOF)?
The timer that holds an output ON for a set time after its input turns OFF, for run-on and cooldown logic.
Read → GlossaryWhat is an off-normal alarm?
A discrete alarm that fires when a device leaves its expected state, like a running pump that stopped or a breaker that opened.
Read → GlossaryWhat Is an On-Delay Timer (TON)?
The most-used PLC timer - preset, accumulator, and done bit - that delays an action after an input turns on.
Read → GlossaryWhat is an out-of-service alarm state?
The ISA-18.2 state for an alarm intentionally removed for maintenance or decommissioning, requiring authorization and tracking.
Read → GlossaryWhat is a PAGA (public address and general alarm) system?
A combined voice-and-tone system that alerts an entire facility, engineered for intelligibility and driven by F&G and ESD.
Read → GlossaryWhat is a pre-alarm?
A low-priority advisory that fires before the main alarm, giving operators lead time to correct a trend before it becomes an excursion.
Read → GlossaryPrepare a Rationalization Workshop
Scope a completable batch, stage every input, pre-sort the easy alarms, and brief the team before the room burns money.
Read → GlossaryReduce Standing Alarm Count
Root-cause the recurring offenders, fix the underlying issue, and close the inflow so the list cannot refill.
Read → GlossaryWhat is a reflash alarm?
Re-annunciation of an acknowledged group when a new or higher sub-condition arrives, so operators are re-alerted.
Read → GlossaryWhat is remote alarm acknowledgment?
Acknowledging an alarm off-site by text reply, push tap, or voice keypress, with audit and security implications.
Read → GlossaryWhy Does the Same Alarm Keep Repeating and How Do You Find the Cause?
How bad-actor frequency analysis isolates a repeating alarm's cause and why fixing repeaters cuts alarm load fastest.
Read → GlossaryRetire an Obsolete Alarm
Confirm it is truly obsolete, remove it through change control from plant and database, and update every dependent record.
Read → GlossaryWhat is a return-to-normal (RTN) alarm event?
The transition of an alarm from active back to normal, confirming a condition cleared as a tracked event.
Read → GlossaryReview Alarm KPIs Monthly
Pull the standard metrics, read them against target, find the bad actors, and open a tracked action for every miss.
Read → GlossaryRun a Rationalization Session
Seat the right roles, bring the right inputs, and drive every alarm through cause, consequence, action, and priority.
Read → GlossarySet Deadband to Stop Chatter
Confirm it is chatter, size deadband against the real noise, and add a short delay only if needed without masking events.
Read → GlossaryHow do you set a gas detector alarm setpoint?
Take the low and high values from the site design in the right units, enter them in order, and prove each drives its annunciation and executive action.
Read → GlossarySet Priority From Consequence
Rate the realistic consequence, estimate the response window, and read priority off the matrix instead of guessing.
Read → GlossaryHow do you suppress alarms by plant mode?
Define the modes, tie suppression to a reliable state signal, suppress only the irrelevant, and keep it visible and reversible.
Read → GlossaryHow do you set up first-out alarm detection?
Group the trip's alarms, latch which came first, mark it distinctly, and rest it on sound time sync and fine resolution.
Read → GlossaryHow do you set alarm and trip setpoints?
Order the limits outward from the operating envelope, size the margins, document each basis, and review every change under MOC.
Read → GlossarySetting API 2350 Alarm Levels
Place overfill levels from a response-time budget, not tank percentage.
Read → GlossaryShelve an Alarm Safely
Confirm it is a nuisance, shelve through the controlled function with a time bound, keep it visible, and escalate repeats.
Read → GlossaryWhat is a shelved and disabled alarm report?
A standing report of every suppressed or disabled alarm, with who did it and when it expires, so bypasses are not forgotten.
Read → GlossaryWhat is an SMS alarm gateway?
The component that sends SCADA alarms as text messages via a local GSM modem or a cloud SMS API.
Read → GlossaryWhat Is a Stale Alarm?
An alarm active far past a threshold like 24 hours, tracked as an ISA-18.2 health metric.
Read → GlossaryWhat is a stale-data alarm?
Fires when a tag has not updated within its expected interval, catching a source that stopped refreshing while comms look up.
Read → GlossaryWhat Is the Difference Between a Standing Alarm and a Fleeting Alarm?
One stays active for hours signalling an unresolved condition, the other flickers in and out - and what each pattern reveals.
Read → GlossaryWhat Is the Difference Between a Trip Setpoint and an Alarm Setpoint?
Why the alarm warns the operator and the trip acts automatically, and how the gap between them buys response time.
Read → GlossaryTune Out Nuisance Alarms
Identify the ignored alarms, diagnose why each adds no value, and apply the matching fix instead of bulk-disabling.
Read → GlossaryValidate Alarm Setpoints
Clear the normal swing, leave enough response time, and size deadband against noise before a setpoint enters the database.
Read → GlossaryHow do you verify a high wet-well overflow alarm?
Confirm the setpoint and datum, inject a level to trip it, keep the high-high independent, and prove the notification reaches a responder.
Read → GlossaryWhat is a voice callout for SCADA alarms?
An automated phone call that reads an alarm aloud and takes a keypad acknowledgment when texts get missed.
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