Why Operators Bypass Alarms: Diagnosing Alarm Fatigue and Systemic Trust Failure

Operators bypass alarms because the frequency of non-actionable alerts has exceeded their cognitive processing limit, leading to alarm fatigue and a psychological phenomenon known as the normalization of deviance. When an industrial control system triggers "nuisance alarms"—alerts that do not require immediate intervention or represent a true deviation from safety—operators begin to perceive the alarm system as an obstacle to production rather than a safety tool. Consequently, bypassing or "shelving" alarms becomes a learned survival mechanism to maintain throughput.

To understand this behavior, one must look beyond individual negligence. According to the ISA-18.2 standard, an operator should ideally handle no more than one to two alarms every ten minutes. In many brownfield environments, operators are bombarded with hundreds of alerts per shift. This volume forces the brain to desensitize itself to the auditory and visual stimuli of the HMI (Human-Machine Interface). When the cost of responding to a false alarm (lost production time) consistently outweighs the perceived risk of ignoring it, bypassing becomes the rational, albeit dangerous, choice.

The Root Causes of Alarm Bypassing

The decision to bypass an alarm is rarely a result of laziness; it is typically a rational response to a poorly configured system. There are three primary systemic drivers:

1. Alarm Fatigue and Cognitive Overload

The human brain is biologically ill-equipped to process high-frequency, low-priority data. When a system generates "chattering alarms"—sensors that oscillate rapidly across a threshold—the operator experiences cognitive overload. If an operator is managing a complex process and receives 50 alerts in an hour, they cannot perform the root cause analysis required for each one. Over time, the "crying wolf" effect takes hold. The operator stops asking "What is wrong with the machine?" and starts asking "How do I make this noise stop?" This is a primary reason why operators ignore maintenance alerts across various manufacturing sectors.

2. The Normalization of Deviance

Coined by sociologist Diane Vaughan, the "normalization of deviance" occurs when people within an organization become so accustomed to a deviant behavior that they no longer consider it deviant. In a plant setting, this looks like a "stale alarm" that has been active for six months. Because the machine hasn't exploded despite the active alarm, the workforce subconsciously concludes that the alarm is "wrong" and the current state is "safe." Bypassing the alarm then becomes a standard operating procedure passed down from senior operators to juniors, creating a systemic trust failure regarding the plant's instrumentation.

3. Poor Alarm Rationalization (Nuisance Alarms)

Many alarms are programmed during the initial commissioning of a plant without a follow-up "rationalization" phase. This leads to:

• Chattering Alarms: A sensor set too close to an operating limit with no deadband, causing it to trigger dozens of times per minute.
• Standing Alarms: Alarms that stay active during normal maintenance or specific product changeovers.
• Consequential Alarms: A single pump failure triggering 20 different low-pressure and low-flow alarms downstream, masking the actual source of the problem.

The Engineering Physics of the Bypass

From a systems engineering perspective, bypassing often occurs because the alarm logic fails to account for the physics of peak production. For example, a motor might be designed to trigger a high-temperature alarm at 90°C. However, during a high-speed summer shift, the motor naturally runs at 92°C without failing. The operator, knowing the motor is fine but tired of the siren, bypasses the alert. The system has failed to adapt to the environmental reality, forcing the human to intervene.

What to Do About It: A Step-by-Step Remediation

Fixing alarm bypass issues requires a shift from punishing operators to optimizing the technical environment.

Step 1: Perform an Alarm Audit (The 80/20 Rule)

Identify the "Top 10" most frequent alarms. In most facilities, 80% of the noise is generated by less than 20% of the alarm tags. Use the ISA-18.2 Management of Alarm Systems framework to categorize these. If an alarm does not require a specific, documented operator action, it should be downgraded to an "event" or "log" and removed from the HMI's audible alerts.

Step 2: Implement Technical Filters

• Deadbands: If a temperature limit is 100°C, set the "clear" signal at 95°C to prevent the alarm from toggling rapidly at the threshold.
• On/Off Delays: Require the condition to persist for 5–10 seconds before alerting the operator to filter out momentary spikes.
• State-Based Alarming: Automatically suppress low-pressure alarms when the pump is intentionally turned off for cleaning or changeovers.

Step 3: Transition to Predictive Monitoring

The fundamental flaw of traditional alarming is that it is reactive—it triggers after a threshold is breached. This is why many preventive maintenance schedules fail; they don't account for the actual condition of the asset.

Modern reliability teams are moving away from simple threshold alarms toward AI-driven pattern recognition. Factory AI offers a solution here: it is a sensor-agnostic, no-code platform that can be deployed in "brownfield" environments in under 14 days. Instead of screaming at an operator when a bearing is already failing, these systems detect subtle harmonic shifts weeks in advance. This allows maintenance to be planned during scheduled downtime, eliminating the "emergency" nature of the alarm and the subsequent temptation to bypass it.

Step 4: Cultural Re-alignment

Management must ensure that operators are never punished for a machine failure that occurred while they were following alarm protocols. Conversely, bypassing a "Critical" or "Safety" ranked alarm must be treated as a significant near-miss event that triggers a formal review, not to punish, but to understand why the operator felt the bypass was necessary.

Related Questions

What is the difference between an alarm and an alert? An alarm requires immediate operator action to prevent an unscheduled shutdown or safety incident. An alert (or event) is a notification of a status change that does not require immediate intervention but should be noted for future maintenance. Confusing the two is a leading cause of alarm fatigue.

How many alarms per hour is considered acceptable? According to EEMUA 191 and ISA-18.2 guidelines, an average of 6 alarms per hour (one every 10 minutes) is considered manageable. Anything exceeding 12 alarms per hour is considered "overloaded," and the operator's ability to respond effectively drops significantly.

Can AI reduce the number of bypassed alarms? Yes. AI reduces bypass rates by filtering out "noise" and providing high-confidence early warnings. By using a platform like Factory AI, plants can move from 1,000 reactive threshold alarms to 10 proactive "health scores," which restores operator trust in the system and ensures that when an alert does fire, it is taken seriously.

What are "chattering" and "stale" alarms? A chattering alarm is one that repeatedly transitions between the alarm and normal states in a short period. A stale alarm is one that remains in the alarm state for an extended period (typically more than 24 hours), often because the underlying condition is considered "normal" by the staff, leading to the normalization of deviance.