Smart Building Management System

Hazard & Risk Analysis (HRA) — ISO/IEC/IEEE 15289 — Report | IEC 61508 Phase 3
Generated 2026-03-27 — UHT Journal / universalhex.org

Hazard Register

Hazard	Severity	Frequency	SIL	Safe State
H-001: Smoke spread via HVAC ducts due to failure to shutdown on fire alarm	catastrophic	low	SIL 3	all supply fans de-energised, smoke extraction fans running, fire dampers closed
H-002: Access control doors fail to release during fire evacuation	catastrophic	low	SIL 3	all access-controlled doors on evacuation routes fail-safe open (electromagnetic locks de-energised)
H-003: HVAC overcooling/overheating from sensor failure	major	medium	SIL 1	HVAC output clamped to safe range (15-28°C), alarm raised to facility manager
H-004: Cyber intrusion via BACnet/Modbus network compromises building systems	critical	low	SIL 2	network isolation — OT network air-gapped from IT, all controllers revert to local standalone mode
H-005: Legionella proliferation from DHW temperature control failure	catastrophic	low	SIL 2	DHW heater energised to maintain >60°C storage, pasteurisation cycle forced, alarm to facilities
H-006: Stairwell pressurisation failure during fire evacuation	catastrophic	low	SIL 3	pressurisation fans running at maximum, stairwell doors held closed by differential pressure

Safety Case Structure (GSN)

Goal Structuring Notation per GSN Community Standard v3. Top goal decomposes into hazard mitigation sub-goals, each supported by SIL-allocated requirements and verification evidence.

flowchart TD
  G0["<b>G0: Top Goal</b><br/>Smart Building Management System is acceptably safe"]
  S0{"<b>S0: Strategy</b><br/>Argument by hazard<br/>mitigation per IEC 61508"}
  G0 --> S0
  G1["<b>G1: H-001</b><br/>Smoke spread via HVAC ducts due to failure to shutdown on fi...<br/>SIL 3"]
  S0 --> G1
  G2["<b>G2: H-002</b><br/>Access control doors fail to release during fire evacuation<br/>SIL 3"]
  S0 --> G2
  G3["<b>G3: H-003</b><br/>HVAC overcooling/overheating from sensor failure<br/>SIL 1"]
  S0 --> G3
  G4["<b>G4: H-004</b><br/>Cyber intrusion via BACnet/Modbus network compromises buildi...<br/>SIL 2"]
  S0 --> G4
  G5["<b>G5: H-005</b><br/>Legionella proliferation from DHW temperature control failur...<br/>SIL 2"]
  S0 --> G5
  G6["<b>G6: H-006</b><br/>Stairwell pressurisation failure during fire evacuation<br/>SIL 3"]
  S0 --> G6

GSN Export (YAML)

Machine-readable safety case structure. Import into GSN tools (Astah GSN, ASCE, NOR-STA).

# GSN Safety Case — Smart Building Management System
# Generated 2026-03-27
# Goal Structuring Notation (GSN) per GSN Community Standard v3

goals:
  G0:
    text: "Smart Building Management System is acceptably safe"
    type: top-goal
    supported_by: [S0]

strategies:
  S0:
    text: "Argument by hazard mitigation per IEC 61508"
    supported_by: [G1, G2, G3, G4, G5, G6]

  G1:
    text: "H-001: Smoke spread via HVAC ducts due to failure to shutdown on fire alarm"
    sil: 3
    safe_state: "all supply fans de-energised, smoke extraction fans running, fire dampers closed"
    supported_by: []
    evidence: []
  G2:
    text: "H-002: Access control doors fail to release during fire evacuation"
    sil: 3
    safe_state: "all access-controlled doors on evacuation routes fail-safe open (electromagnetic locks de-energised)"
    supported_by: []
    evidence: []
  G3:
    text: "H-003: HVAC overcooling/overheating from sensor failure"
    sil: 1
    safe_state: "HVAC output clamped to safe range (15-28°C), alarm raised to facility manager"
    supported_by: []
    evidence: []
  G4:
    text: "H-004: Cyber intrusion via BACnet/Modbus network compromises building systems"
    sil: 2
    safe_state: "network isolation — OT network air-gapped from IT, all controllers revert to local standalone mode"
    supported_by: []
    evidence: []
  G5:
    text: "H-005: Legionella proliferation from DHW temperature control failure"
    sil: 2
    safe_state: "DHW heater energised to maintain >60°C storage, pasteurisation cycle forced, alarm to facilities"
    supported_by: []
    evidence: []
  G6:
    text: "H-006: Stairwell pressurisation failure during fire evacuation"
    sil: 3
    safe_state: "pressurisation fans running at maximum, stairwell doors held closed by differential pressure"
    supported_by: []
    evidence: []

solutions: