Powder actuated tools are most often used to drive nails into concrete. The design is similar to a long-barreled hand-gun except it has a piston in the barrel that actuates a nail which is held in the muzzle temporarily with a nylon grommet. Firearms maker, Remington, is among several prominent manufacturers. There are a wide variety of powder actuated tools, many with varying trigger mechanisms. Repair varies depending on the individual product, but the repair process is similar.
Remove nails or any other object from the bore. Never look into the bore; just observe from the side.
Clean the tool thoroughly with a commercial gun powder solvent. This is the most common source of malfunctioning. These tools are very prone to gun powder fouling where gunpowder residue affects the function of the tool or causes the breech to jamb -- often with a shell casing in it.
With the tip of the gun pointed down, pour the gunpowder solvent into the breech. Hold the tool sideways and pour more solvent into the breech, letting it flow into and behind the breech mechanism and soak thoroughly.
Open the breech and apply more solvent. Open and close the breach thoroughly as it's soaking with solvent, working the powder fouling free of the moving parts and wiping residue away with a cloth or paper towel.
Insert the rod from a barrel cleaning kit and, with the breech open, press the barrel rod-down on the ground to eject a jammed cartridge after the solvent cleaning.
Disassemble the tool and replace any damaged parts if the thorough solvent cleaning and cartridge removal fail to solve the problem.