There are several major risk factors that can lead to a nail gun injury including:
Understanding these hazards will help you to prevent injuries on the jobsite. This module will take a closer look at these important risk factors and hazards.
Unintended nail discharges from double fires usually occurs when using contact firiing triggers.
The Consumer Product Safety Commission (CPSC) found contact trigger nailers are susceptible to double firing. This occurs a lot when workers are trying to accurately place the nailer against the work piece. Researchers found a second unintended firing can happen faster than the user is able to react and release the trigger.
Double fire can also be a particular problem for new workers who may push harder on the tool to compensate for recoil. It can also happen when the user is in an awkward position, such as tight work spaces, where the gun doesn't have the necessary space to recoil. The recoil of the gun can also cause a non-nail injury in tight spaces if the nail gun hits the user's head or face.
Nail guns with contact and single actuation triggers will fire if the trigger is being squeezed and the safety contact tip gets knocked or pushed into an object or person by mistake. For example, a framer might knock his leg going down a ladder or bump into a co-worker passing through a doorway. Contact trigger nailers can release multiple nails and single actuation trigger nailers can release a single nail to cause injury.
Holding or carrying contact firing trigger or single actuation trigger nail guns with the trigger squeezed increases the risk of unintended nail discharge. Construction workers tend to keep a finger on the trigger because it is more natural to hold and carry an 8-pound nail gun using a full, four-finger grip. Tool manufacturers, however, do warn against it.
A contractor was on a roof with a framing nailer. He had his finger on the trigger with the autofire engaged. However, when he sat up from a crouched position, he accidentally pushed the tip of the gun against his knee, causing the gun to fire. The nail grazed his bone inside his leg and he was unable to straighten his leg. Paramedics had to carry him off the roof and down the stairs. He didn't have to undergo surgery, as doctors were able to remove the nail.
This can happen with ALL trigger types. Nails can pass through a work piece and either hit the worker’s hand or fly off as a projectile nail. A blow-out nail is just one example. Blow-outs can occur when a nail is placed near a knot in the wood. Knots involve a change in wood grain, which creates both weak spots and hard spots that can make the nail change direction and exit the work piece.
Nail penetration is especially a concern for placement work where a piece of lumber needs to be held in place by hand. If the nail misses or breaks through the lumber it can injure the non-dominant hand holding it, or as you can see in the image to the right, some other part of the body.
Two framers were working together to lay down and nail a subfloor. One framer was waiting and holding the nail gun with his finger on the contact trigger. The other framer was walking backwards toward him and dragging a sheet of plywood. The framer handling the plywood backed into the tip of the nail gun and was shot in the back. The nail nicked his kidney, but fortunately he recovered. As a result of this incident, the contractor switched to using only sequential triggers on framing nail guns. Co-workers can get injured if they bump into your contact trigger nail gun. You can prevent this by using a full sequential trigger.
When a nail hits a hard surface, it has to change direction and it can bounce off the surface, becoming a projectile. Wood knots and metal framing hardware are common causes of ricochets. Problems have also been noted with ricochets when nailing into dense, laminated beams. Ricochet nails can strike the worker or a co-worker to cause an injury. This can happen with ALL trigger types.
Injuries may occur when the tip of the nail gun does not make full contact with the work piece and the discharged nail becomes airborne. This can occur when nailing near the edge of a work piece, such as a plate. Positioning the safety contact is more difficult in these situations and sometimes the fired nail completely misses the lumber. Injuries have also occurred when a nail shot through plywood or oriented strand board sheeting missed a stud and became airborne. This can happen with ALL trigger types.
Nailing in awkward positions where the tool and its recoil are more difficult to control may increase the risk of injury. These include:
"Toe-nailing" is driving a nail in at a slant to secure floor joists to the plate. It’s more likely to cause an injury because the user cannot hold the gun flush against the workpiece.
Nailing from a ladder also makes it difficult to position the nail gun accurately. Nailing beyond a comfortable reach distance from a ladder, elevated work platform, or leading edge places the user at risk for a fall.
While injuries can happen with all trigger types when working in awkward positions, accidental discharges using single-action triggers are a special concern.
This unsafe practice can occur with all trigger types. Bypassing or disabling features of either the trigger or safety contact tip is an work practice that increases the risk of injury. A worker may believe it's more efficient to bypass safety mechanisms, but all it takes is one mistake to eliminate any benefit.
For example, removing the spring from the safety contact tip makes an unintended discharge even more likely. Modifying tools can lead to safety problems for anyone who uses the nail gun.
Nail gun manufacturers strongly recommend against bypassing safety features, and voluntary standards prohibit modifications or tampering. OSHA's Construction Standard at 29 CFR 1926.300(a) requires all hand and power tools and similar equipment, whether furnished by the employer or the employee shall be maintained in a safe condition. Nail guns that have modified safety mechanisms must be repaired or taken out of service.
Pneumatic tools and compressor use are regulated under OSHA’s Construction Standard at 29 CFR 1926.302(b). The provisions in this standard that are relevant for nail guns are provided below.
Pneumatic nail guns produce short (less than a tenth of a second in duration) but loud "impulse" noise peaks: one from driving the nail and one from exhausting the air. Most nail gun manufacturers recommend users wear hearing protection when using a nailer.
Nail gun noise can vary depending on the gun, the work piece, air pressure, and the work setting. The type of trigger system does not appear to affect the noise level. The sound level from pneumatic nail guns average 94.5 dBA and peak noise emission levels for several nailers can range from 109 to 136 dBA. These loud short bursts can contribute to hearing loss.
Employers should provide hearing protection in the form of earplugs or muffs and make sure they are worn correctly. Employers should also ask about noise levels when buying nail guns.
Methods to reduce nail gun noise include:
Framing nail guns can weigh up to 8 pounds and many framing jobs require workers to hold and use nail guns for long periods of time while working in awkward postures. Using nail guns for tasks that require awkward postures is likely the cause for most ergonomic injuries.
Holding an 8-pound weight for long periods of time can lead to musculoskeletal symptoms such as soreness or tenderness in the fingers, wrist, or forearm tendons or muscles. These symptoms can progress to pain, or in the most severe cases, inability to work.
If use of a nail gun is causing musculoskeletal pain or symptoms of musculoskeletal disorders, medical care should be sought. The probability and severity of ergonomic injuries while using nail guns may be eliminated or reduced by:
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