The only difference between this hand tool and a handgun is that the bullet is a pin. Don't be caught looking down its barrel.

It’s coffee time. The carpenter at the construction project is working with a powder actuated tool to attach strapping to a concrete wall when he hears the lunch truck blowing its horn outside. He immediately puts down the tool and goes to join the line for coffee. When he comes back, he starts chatting with the plumber who hadjoined him for the break.
Without thinking, the plumber casually picks up the powder actuated tool and points it at the wall. He pulls on the trigger a few times. Nothing happens. He keeps talking with the carpenter and cocks the gun. He aims at the wall and again pulls on the trigger. Nothing happens. He pushes the tool against the wall and notices that the guard on the muzzle is spring loaded and that it moves in and out. Curious, he puts his hand over the muzzle and pushes on it to test the strength of the spring. At the same time, he pulls the trigger again. This time it fires, and the plumber seriously injures two of his fingers.

Powder actuated tools are as dangerous as handguns. Referred to as "powder actuated" or "explosive actuated", these tools use a powder charge to fire a pin or fastener into hard materials such as concrete, mild steel or masonry.

There are two types of powder actuated fastening tools: direct-acting and indirectacting. In a direct-acting tool, the "load" essentially a firearm cartridge without the lead bullet - acts directly against the fastener so that it is shot out the barrel of the tool, usually at high velocity, into the material. In an indirect-acting tool, the load acts on a piston within the tool’s barrel, which in turn drives the fastener that is sitting at the end of the barrel. Because the mass of the piston acts on the pin, the pin’s velocity does not need to be as high as in a direct-acting tool.

Most powder actuated tools used in construction are low velocity. That wasn’t always the case. When the tools were first introduced in 1947, most were direct-acting, high-velocity. If the pin ricocheted or "fish-hooked" in the material, it could easily fly across a room with sufficient velocity to injure either the operator or a bystander. Many accidents occurred because of the high velocity of the tools. However, powder actuated tools today are almost all indirect-acting, low velocity (because the fastener has a low velocity, it is very rare for the pin to ricochet). In fact, many provinces discourage or do not allow the use of high-velocity tools, and most powder actuated tool manufacturers will not supply pins and loads for these tools anymore. Anyone who still has a high-velocity tool should consider retiring it immediately. It takes two separate actions to fire a powder actuated tool. First, the muzzle must be pressed squarely against the work surface with at least five pounds of force to release the spring-loaded safety device that blocks the trigger. Then, with the tool in position, the trigger must be pulled.

There are many different regulations across Canada regarding the use of powder actuated tools. They can be found in the occupational heath and safety legislation for each province under "explosive actuated fastening tool"
. Most provincial regulations require that only a qualified operator trained by the tool manufacturer or a related agent operate the tool. Most manufacturers of powder actuated tools offer free, standard training programs for operators and instructors. After training, operators and instructors are issued certificates stating that they are qualified to operate a tool and/or to train others.

Accidents involving powder actuated tools, like the one described above, are rare. When incidents do happen, it is usually because of improper handling. The most common accident is accidental firing of the tool on oneself, followed by injuries to the eyes from the base material breaking and debris being propelled upward. Also, longterm use of powder actuated tools without hearing protection can result in hearing loss. Operators should be wearing hearing protection, eye protection and a face shield. Heavy shirts and pants provide some protection against ricochets and flying fragments of materials and fasteners.

Always check if a powder actuated tool is loaded when you pick it up. This is the most important and primary safety precaution. The most common injury occurs when people fire a tool thinking it is not loaded. (This has even happened to instructors when, for example, they are not looking and a student loads the gun and puts it back down.) It is also important to read the instructions carefully for each model of tool.
Never place your hand or fingers over the front (muzzle) end of the tool. Also, never alter parts for use in the tool. This can affect the built-in safety features of the tool. Operators and people working within the vicinity must be wearing eye and hearing protection.
Before fastening with the tool (after making sure it is unloaded), conduct the functional check described in each tool’s manual. Without a fastener, push the tool against the work surface and pull the trigger (you should hear the firing mechanism click), then release the tool from the work surface. Carry out several functional tests to ensure the cocking slide and firing mechanism operate freely. (Check the tool’s manual for specific details.) A powder actuated tool should only be used on poured concrete, structural steel, and hollow and grout filled masonry units. Do not try to guess the hardness of a material. And never fire into very hard or brittle materials such as cast iron, tile, glass or rock. These can shatter and result in injury.

Before fastening into any unidentified material, check to see if it is too hard, too soft or too brittle by using the "centre-punch test": Try to drive a pin into the material using a standard hammer. (Wear eye protection during this test.)
Do not use the powder actuated tool on the material if, a) the fastener point is flattened (the material is too hard); b) the fastener penetrates the material easily (the material is too soft); or c) the material cracks or shatters (the material is too brittle).
If the pin makes a small indentation, the material is suitable. Next, as a final safety measure, test fire into the base material using the lowest power level load for the tool being used.

There are acceptable fastener placement and penetration guidelines for concrete and steel. If fastening into concrete, do not fasten closer than 76 millimeters (three inches) from the edge; do not fasten closer than 76mm (three inches) to another fastener; and concrete must be at least three times as thick as the fastener penetration.
If fastening into steel, do not fasten closer than 13mm (a half inch) from the edge; do not fasten closer than 38mm (1-1/2 inches) to another fastener; and the steel must be at least as thick as the fastenershank diameter.

Again, it is important to follow the instructions supplied with the tool. The loads used in powder actuated tools come in different power levels. The load levels are designated by numbers, marked on each box of loads: As the number increases, the power level increases. Power level is also indicated by the colour of the box, or the colour on each load. Loads of different power levels should not be mixed together - the operator may pick up the wrong power level load.

Tools should be cleaned according to the manufacturer’s instructions to ensure the parts continue to move freely. In general, the piston rod, barrel assembly, and receiver should all be cleaned on a daily basis. And the piston should be checked for damage.

Powder actuated tools are safe if care and common sense are applied. Again, most injuries are caused by accidental firing: Users should be trained to always unload a tool and always check to see if a tool is loaded when they pick it up. Ultimately, operators should treat the tools with the same respect they would a handgun.