A fastener driving apparatus for driving fasteners into a substrate. The fastener driving apparatus is a combination of a motor driven linear motion converter; a compression cylinder; an expansion cylinder and a valve arrangement. The linear motion converter converts a rotational motion of a motor to a linear motion of a compression piston within the compression cylinder causing a gas within the compression cylinder to be compressed. The compressed gas is communicated to the expansion cylinder through the valve arrangement wherein the compressed gas expands causing an anvil coupled to an expansion piston within the expansion cylinder to move axially. The axial movement of the anvil causes a fastener to be driven into the substrate. The fastener driving apparatus is an ergonomically designed portable hand held tool providing comfort to a user, meeting safety standards and performance efficiency requirements.