Nail guns are used in connection with virtually every kind of carpentry including framing, roofing, flooring and finishing. Some nail guns are powered by electricity or gas, but most use compressed air. These pneumatic nail guns vary in their application and power, but all are commonly triggered by one of two different mechanisms: contact and sequential triggers. These mechanisms may look the same but they can pose significantly different degrees of risk to operators.

Contact trip trigger mechanisms allow the user to fire the tool at any time the trigger and the nose of the gun — the contact element — are both depressed. This enables “bump nailing:” When the operator depresses the trigger, and bumps the nose of the nailer against a surface, the gun will fire. Research shows that nail guns with contact triggers carry twice the risk of acute injury of those with sequential triggers.

Sequential triggers require the nose of the gun — the contact element — be depressed before the trigger can be pulled. That helps avoids inadvertent discharge of nails. Research shows that tools with sequential triggers carry half the risk of acute injury associated with contact triggers.

Just how do nail guns work? See this presentation prepared by the staff of the Sacramento Bee, which is part of a series on nail gun safety produced by the newspaper.  Click here.