Powder-Actuated Tools (PAT) and Associated Hazards

A powder-actuated tool (PAT, often generically called a Hilti gun or a Ramset gun after their manufacturing companies) is a type of nail gun used in construction and manufacturing to join materials to hard substrates such as steel and concrete. Known as direct fastening or explosive fastening, this technology is powered by a controlled explosion of a small chemical propellant charge, similar to the process that discharges a firearm.

In fact, they are so dangerous that they must be operated only by specially trained employees.

When using powder-actuated tools, an employee must wear suitable ear, eye, and face protection. The user must select a powder level – high or low velocity – that is appropriate for the powder-actuated tool and necessary to do the work without excessive force.

The muzzle end of the tool must have a protective shield or guard centered perpendicular to and concentric with the barrel to confine any fragments or particles that are projected when the tool is fired. A tool containing a high-velocity load must be designed not to fire unless it has this kind of safety device.

To prevent the tool from firing accidentally, two separate motions are required for firing. The first motion is to bring the tool into the firing position, and the second motion is to pull the trigger. The tool must not be able to operate until it is pressed against the work surface with a force of at least 5 pounds (2.2 kg) greater than the total weight of the tool.

If a powder-actuated tool misfires, the user must hold the tool in the operating position for at least 30 seconds before trying to fire it again. If it still will not fire, the user must hold the tool in the operating position for another 30 seconds and then carefully remove the load in accordance with the manufacturer’s instructions. This procedure will make the faulty cartridge less likely to explode. The bad cartridge should then be put in water immediately after removal. If the tool develops a defect during use, it should be tagged and must be taken out of service immediately until it is properly repaired.

Safety precautions that must be followed when using powder-actuated tools include the following:

• Do not use a tool in an explosive or flammable atmosphere.
• Inspect the tool before using it to determine that it is clean, that all moving parts operate freely, and that the barrel is free from obstructions and has the proper shield, guard, and attachments recommended by the manufacturer.
• Do not load the tool unless it is to be used immediately.
• Do not leave a loaded tool unattended, especially where it would be available to unauthorized persons.
• Keep hands clear of the barrel end.
• Never point the tool at anyone.

When using powder-actuated tools to apply fasteners, several additional procedures must be followed:

• Do not fire fasteners into material that would allow the fasteners to pass through to the other side.
• Do not drive fasteners into very hard or brittle material that might chip or splatter or make the fasteners ricochet.
• Always use an alignment guide when shooting fasteners into existing holes.
• When using a high-velocity tool, do not drive fasteners more than 3 inches (7.62 centimeters) from an unsupported edge or corner of material such as brick or concrete.
• When using a high-velocity tool, do not place fasteners in steel any closer than 1/2-inch (1.27 centimeters) from an unsupported corner edge unless a special guard, fixture, or jig is used.