August 12, 2026

A Pinhole Can Be Deadly to a Lineman

A pinhole can be deadly.

That is why each year the Association of Missouri Electric Cooperatives’ Rob Gerling and Brian Prenger arrive at SEMO Electric Cooperative with a trailer full of industrial-sized washing machines, dryers and specialized testing equipment to clean, inspect and electrically test the cover-up equipment used by lineworkers.

The bright orange and black rubber blankets and line hoses are designed to cover energized equipment and power lines, helping protect workers from accidental contact with electricity. Insulated fiberglass tools, including shotgun sticks used to install and remove protective equipment from a safe distance, are also inspected and tested.

Using high-voltage testing equipment, Gerling and Prenger send tens of thousands of volts through each piece of rubber protection, searching for microscopic holes, tears and defects that cannot be detected by the naked eye. Even the smallest flaw can allow electricity to pass through the material, creating a potentially fatal situation for a worker who is also in contact with a grounded surface.

While every blanket, hose and insulated tool is thoroughly tested, lineworkers also inspect their equipment before each use, looking for signs of damage, wear or deterioration. In the electric utility industry, these inspections are more than a routine procedure—they are a critical safeguard. When working around energized power lines, the difference between a safe day and a tragedy can be as small as a pinhole.

The Association of Missouri Electric Cooperatives’ Rob Gerling inspects and cleans a fiberglass jib insert used on a bucket truck during energized line work. The jib insert extends the reach of the truck’s boom while providing electrical insulation between the equipment and energized power lines, helping lineworkers safely perform work around high-voltage electricity.
The Association of Missouri Electric Cooperatives’ Brian Prenger, left, discusses the cover-up equipment testing process with SEMO Electric Cooperative linemen Brandon Church, center, and Hunter Hardin. The circled photo shows a microscopic tear discovered during testing. Defects too small to be seen by the naked eye can compromise protective equipment and create a life-threatening hazard for lineworkers working around high-voltage electricity.