Safety Sign Signal Words — ANSI Z535.2 DANGER vs WARNING vs CAUTION vs NOTICE, ISO 3864-2 Two-Level System, and the Schema for AI Agents

The ANSI Z535.2 Four-Word Signal System

NOTICE vs CAUTION — The Non-Injury Boundary

NOTICE and CAUTION are frequently confused. The distinction is binary: does the situation involve risk of personal injury or not?

• CAUTION (yellow): Minor injury possible — slip on wet floor, bang head on low beam, catch finger on sharp edge. Some bodily harm could result.
• NOTICE (blue): No personal injury risk — the sign communicates property damage risk, procedural requirements, or policy. No one will be hurt if the message is ignored, but equipment may be damaged or policy violated.

Failure Mode 1 — CAUTION Used for Fatal Hazards

The most significant signal word error is using CAUTION for hazards that meet DANGER or WARNING criteria. This is not merely an aesthetic issue — ANSI Z535.2 Section 6.1 states that signs must "accurately reflect the hazard severity." Using CAUTION for a lethal hazard is a standards non-compliance that can have legal liability implications when a worker is injured relying on the sign's severity signal.

Fall Arrest Sign Severity Levels

// Correct signal word encoding for common safety hazards

// Electrical panel — exposed live conductors above 50V
sign.signal_word          = "DANGER"   // Contact WILL cause death
sign.hazard_panel_color   = "red"
sign.hazard_category      = "electrical"
sign.involves_injury_risk = true

// Arc flash boundary marker
sign.signal_word          = "WARNING"  // Arc flash CAN cause serious injury
sign.hazard_panel_color   = "orange"
sign.hazard_category      = "arc-flash"
sign.involves_injury_risk = true

// Wet floor (mopped corridor, low slip risk)
sign.signal_word          = "CAUTION"  // Slip MAY cause minor injury
sign.hazard_panel_color   = "yellow"
sign.hazard_category      = "slip"
sign.involves_injury_risk = true

// Employee-only area (no injury risk)
sign.signal_word          = "NOTICE"   // No injury — access control only
sign.hazard_panel_color   = "blue"
sign.hazard_category      = "access-control"
sign.involves_injury_risk = false

Failure Mode 2 — ANSI Z535.2 vs ISO 3864-2 Compliance Conflated

ANSI Z535.2 (US) and ISO 3864-2 (international) have different signal word systems. A safety sign catalog must encode which standard applies — claiming dual compliance without meeting both is inaccurate and may expose buyers to compliance risk:

// ANSI Z535.2 sign — US facility
sign.compliance_standard    = "ANSI-Z535.2"
sign.ansi_z535_section      = "Z535.2"
sign.signal_word            = "WARNING"
sign.hazard_panel_color     = "orange"      // ANSI WARNING = orange

// ISO 3864-2 sign — international/EU
sign.compliance_standard    = "ISO-3864-2"
sign.signal_word            = "WARNING"
sign.hazard_panel_color     = "yellow"      // ISO WARNING = yellow (note: different from ANSI)
sign.iso_7010_symbol        = "W011"        // Mandatory for ISO signs

// Dual-standard sign (genuinely compliant with both)
sign.compliance_standard    = "both"
sign.ansi_z535_section      = "Z535.2"
sign.iso_7010_symbol        = "W011"        // ISO 7010 symbol satisfies both standards

Failure Mode 3 — Missing Pictogram Encoding for Mandatory Symbol Signs

Under ISO 3864-2, safety pictograms are mandatory components of hazard signs. Under ANSI Z535.2, pictograms are strongly recommended and effectively required for compliance with OSHA's General Duty Clause intent. Safety signs sold without a safety symbol when one is required for the hazard type represent a compliance gap.

ISO 7010 Common Symbols for Safety Signs

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