What must be present on the muzzle of a power-driven nailer and stapler to prevent accidental fastener ejection?

A safety device must be present on the muzzle of a power-driven nailer and stapler to prevent accidental fastener ejection. This safety mechanism is crucial because it helps ensure that fasteners are only discharged when the tool is properly positioned against the work surface and the operator intentionally activates the tool.

The purpose of the safety device is to minimize the risk of accidental shootings, which can lead to injuries. It helps create a controlled operating environment by requiring certain conditions to be met before the fastener can be ejected. The presence of this device is a standard requirement in safety regulations to protect both the operator and those nearby during use.

Other components mentioned, such as a trigger safety, while important in some tools, do not specifically address the need for a muzzle mechanism directly related to fastener expulsion. A sound barrier and exhaust vent serve entirely different functions related to noise reduction and exhaust management, respectively, which do not contribute to preventing accidental fastener ejection.