Heinrich's Law illustration
Safety / Management / Risk
Safety / Management / Risk

Heinrich's Law

Serious failures rarely come from nowhere; they sit atop a pyramid of smaller signals.

Popularity
Usefulness
Aliases
Hain's law / accident triangle / 1:29:300 rule / safety pyramid
Domains
Safety engineering, aviation, operations, risk management, quality

Definition

  • Heinrich's Law holds that behind every serious accident there are many minor incidents and a far larger number of near misses and latent hazards, so small warnings should be treated as signals of larger risk.

Core Idea

  • Serious failures rarely come from nowhere; they sit atop a pyramid of smaller signals.
  • For every major accident there are roughly 29 minor injuries and 300 near misses (and many latent risks).
  • Acting on small incidents prevents the rare catastrophe.

How It Works

  • The same unsafe conditions produce mostly near misses, occasionally minor harm, and rarely disaster.
  • Ignoring frequent small signals lets the underlying hazard persist.
  • Reducing minor incidents shrinks the base of the pyramid and the chance of the top event.

Usage Example

  • An airline that rigorously logs and investigates every minor anomaly and near miss catches systemic issues before they cause a crash.

Famous Example

  • Example: Herbert William Heinrich's 1:29:300 ratio, echoed in aviation safety as "Hain's law" (behind every serious accident lie 29 minor ones, 300 near misses, and 1,000 hidden hazards).
  • Why it fits this rule: It quantifies the warning pyramid beneath major accidents.
  • Verification status: The ratio is an influential heuristic; the exact numbers are dated and debated, but the principle of escalating signals is widely accepted.

Use Cases / Situations Where It Applies

  • Safety management and incident reporting.
  • Aviation, industrial, and operational risk.
  • Quality systems that track defects and near misses.

When Not to Use or Common Misuse

  • Do not treat the 1:29:300 numbers as exact across all settings.
  • Do not assume reducing minor injuries alone prevents all major ones (some major events have distinct causes).
  • Do not ignore systemic/organizational factors by focusing only on counts.

Rule Invention / Origin

  • Invented by: Herbert William Heinrich; the aviation variant is associated with the name "Hain/Heinrich."
  • Year of invention: 1931 (Heinrich's industrial safety work).
  • Country / context of origin: United States industrial safety; later aviation.

Evidence / Research Basis

  • The accident-triangle concept underpins modern safety practice, though contemporary research refines and critiques the fixed ratios.