Spinning long bolts by hand in tight engine bays is slow and tedious. An air ratchet solves this by using compressed air to spin a socket wrench head. It looks like a standard socket wrench but features a pneumatic motor inside the handle. Squeezing the trigger paddle spins the drive anvil, backing out or running down fasteners in seconds.
Air ratchets do not have high torque like impact wrenches. They are designed for speed, not breaking stuck bolts loose. If a bolt is seized, use the air ratchet like a manual wrench to break it loose first, then squeeze the trigger to spin it the rest of the way out. Keep your fingers clear of the ratchet head, as the tool can easily pinch your hand against surrounding engine parts when it spins.