What Are Proper Safety Distances for Guarding Openings to Prevent Access to Hazards?

Proper safety distances refer to the minimum required space between a guarding opening and a hazardous zone, designed to prevent a person from reaching through the guard and contacting a dangerous part of the machine. These distances are based on human body dimensions and are essential for meeting OSHA and ANSI machine safety requirements.

Key Reference:

ANSI/CSA B11.19 and ISO 13857 provide detailed tables specifying minimum safe distances based on opening size and shape (e.g., mesh, slots, holes) and the location of the hazard.

Common Safety Distance Guidelines:

• Openings ≤ ½ inch (12 mm): No minimum distance required—fingers cannot reach through.

• Openings of ¾ inch (19 mm): Hazard must be at least 4 inches (100 mm) away to prevent finger access.

• Openings of 1 ¼ inch (32 mm): Hazard must be at least 5 ½ inches (140 mm) away to prevent hand access.

• Openings ≥ 2 inches (50 mm): Distance increases significantly to prevent arm or full body access.

Why It Matters:

Improper safety distance allows access to pinch points, rotating parts, or other hazardous areas—even if a guard is present. OSHA 1910.212 requires that guards “prevent the operator from having any part of their body in the danger zone during the operating cycle.”

Summary:

• Always measure from the nearest guarding opening to the hazard.

• Use ANSI/ISO safety distance tables to determine the minimum allowable separation.

• Consider mesh size, slot orientation, and likelihood of access during risk assessment.