2.3 Hierarchy of Controls (Elimination to PPE)

2.3 Hierarchy of Controls (Elimination to PPE)

Introduction to the Hierarchy of Controls

The Hierarchy of Controls is a structured, universally recognized framework used in occupational health and safety to determine the most effective strategies for eliminating or reducing exposure to hazards. Mandated under DOLE Department Order No. 198-18 and international standards such as ISO 45001, the hierarchy dictates that hazard mitigation must follow a strict order of priority.

The controls are arranged from most effective at the top to least effective at the bottom:

  +--------------------------------------------------------+  MOST EFFECTIVE
  |  1. ELIMINATION       (Physically remove hazard)      |
  +--------------------------------------------------------+
  |  2. SUBSTITUTION      (Replace the hazard)            |
  +--------------------------------------------------------+
  |  3. ENGINEERING       (Isolate people from hazard)   |
  +--------------------------------------------------------+
  |  4. ADMINISTRATIVE    (Change the way people work)   |
  +--------------------------------------------------------+
  |  5. PPE               (Protect worker with PPE)      |  LEAST EFFECTIVE
  +--------------------------------------------------------+

Reliability Principle

Controls at the top (Elimination, Substitution, Engineering) physically remove the hazard or place an automated physical barrier between the hazard and the worker. They operate independently of human behavior. Conversely, controls at the bottom (Administrative, PPE) rely entirely on human behavior, supervision, and continuous compliance, making them inherently less reliable.

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Level 1: Elimination (Most Effective)

Elimination involves physically removing the hazard completely from the workplace environment. It is the absolute gold standard of hazard control.

• Mechanism: If the hazard no longer exists, the risk drops to zero.
• Implementation Phase: Elimination is easiest to achieve during facility design or process planning (Prevention through Design - PtD).
• Industrial Examples:
  • Eliminating high-altitude roof maintenance by installing equipment at ground level.
  • Eliminating manual lifting of 50 kg cement bags by installing automated pneumatic conveyor pipelines.
  • Discontinuing toxic solvent-based degreasers in favor of automated ultrasonic hot-water cleaning.

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Level 2: Substitution

Substitution involves replacing a hazardous material, machine, or process with a less hazardous alternative.

• Mechanism: Operation continues, but inherent risk is significantly downgraded.
• Caution: The SO2 must evaluate replacements to avoid introducing new hazards (regrettable substitution).
• Industrial Examples:
  • Substituting lead paints with non-toxic water-based acrylic paints.
  • Replacing volatile organic solvents (benzene, toluene) with citrus-based bio-solvents (d-limonene).
  • Substituting noisy air compressors (105 dBA) with quiet rotary screw compressors (72 dBA).
  • Replacing AC high-voltage power tools with 12V DC battery-operated cordless tools in damp work areas.

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Level 3: Engineering Controls

Engineering Controls involve physical modifications to equipment, structures, or ventilation systems to isolate workers from a hazard.

• Mechanism: Hazard remains in the workplace, but physical barriers or mechanical systems prevent human contact.
• Key Feature: Operates automatically and does not depend on worker compliance.
• Primary Categories of Engineering Controls:
  1. Enclosure & Isolation: Encasing hazards in sealed containers or soundproof rooms (e.g., acoustic enclosures around generators, glove boxes).
  2. Machine Guarding: Installing fixed barriers, interlocked guards, or light curtains on power presses and lathes (DOLE Rule 1200).
  3. Ventilation Systems:
     • Local Exhaust Ventilation (LEV): Captures chemical fumes, dust, or welding smoke directly at origin before entering breathing zones.
     • General Dilution Ventilation: Dilutes contaminant concentrations by introducing fresh outdoor air.
  4. Ergonomic Engineering: Height-adjustable scissor-lift tables, hydraulic drum lifters, and anti-vibration tool mounts.

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Level 4: Administrative Controls

Administrative Controls establish policies, procedures, schedules, and training programs to alter how work is performed, reducing exposure duration or frequency.

• Mechanism: Controls worker behavior and work organization rather than modifying physical equipment.
• Limitation: Vulnerable to human error, fatigue, complacency, or supervision lapses.
• Key Types of Administrative Controls:
  • Standard Operating Procedures (SOPs): Written mandatory step-by-step safe work instructions.
  • Job Rotation: Rotating workers among tasks (e.g., 2 hours on a noisy stamping press, 6 hours in a quiet office) to keep daily exposure below DOLE Rule 1074 limits.
  • Workplace Scheduling: Scheduling high-hazard tasks during off-peak hours or night shifts when fewer employees are present.
  • Permit-to-Work (PTW) Systems: Formal authorization systems for high-risk work such as hot work, confined space entry, and high-voltage servicing.
  • Safety Training: Mandatory OSH orientation, BOSH training, toolbox meetings, and emergency drills.
  • Warning Signs & Markings: Posting safety signs (under DOLE Rule 1080), floor line markings, and visual warnings.

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Level 5: Personal Protective Equipment (PPE) (Least Effective)

Personal Protective Equipment (PPE) includes wearable clothing and equipment designed to protect individual workers from workplace hazards.

• Mechanism: Places a physical barrier directly on the worker's body.
• Why PPE is the Last Line of Defense:
  1. PPE does not eliminate or reduce the hazard itself; the hazard remains at full strength.
  2. If PPE fails, is damaged, fits improperly, or is removed by the worker, exposure occurs immediately.
  3. PPE can cause discomfort, restrict movement or vision, and induce heat stress.
• Requirement: Mandated under DOLE Rule 1080 when higher-tier controls are technically infeasible or while engineering controls are being installed.

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Defense-in-Depth: Combining Controls

Effective safety programs utilize Defense-in-Depth by combining multiple layers from different levels of the hierarchy (e.g., using low-VOC paint [Substitution] inside a downdraft LEV booth [Engineering] with worker rotation [Administrative] and respirators [PPE]).