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Software Architecture Guide

Hazard Warning

Explanation

Section titled “Explanation”

Hazard warning is one of five Safety sub-characteristics in ISO/IEC 25010. The product provides warnings of unacceptable risks. The warnings go to operations or to internal controls. Safety was added in the 2023 revision, which has nine quality characteristics. See the articles ISO/IEC 25010 Product Quality Model and Safety.

The other four Safety sub-characteristics

  • Operational constraint: the product keeps its operation within safe parameters or states when it meets an operational hazard.
  • Risk identification: the product can identify event sequences or operations that could expose life, property or the environment to unacceptable risk.
  • Fail safe: after a failure, the product automatically enters a safe operating mode or returns to a safe condition.
  • Safe integration: the product stays safe during and after integration with other components.

Where hazard warning fits

Hazard warning is about telling someone or something about a risk. The other four cover identifying risk, limiting operation, handling failure, and combining components safely.

An alarm design problem

Too many warnings can defeat the purpose. Alarm flood means too many alarms sound during a plant upset. EEMUA 191 and ANSI/ISA-18.2 are the main alarm management guidelines.

Example

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A generic machine-monitoring system detects a risky condition. It sends one warning to the operator console. It also sends a signal to an automatic internal control. Either can then react. The team checks that a single upset does not trigger a flood of alarms.

Trade-offs

Section titled “Trade-offs”

More warnings do not mean more safety. Too many alarms at once, known as alarm flood, make the important ones hard to act on. Alarm management guidelines such as EEMUA 191 and ANSI/ISA-18.2 address this.

Checks

Section titled “Checks”
  • The document states who receives risk warnings: operations, internal controls, or both.
  • Hazard warning is distinguished from operational constraint, risk identification, fail safe and safe integration.
  • The design addresses alarm flood during upsets.
Section titled “Related”

Sources

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