Unplug the air ratchet from the power supply, if it's still plugged in.
Use a lint-free washcloth to clean dirt, dust and debris from the trigger area. If you don't regularly clean the area, a buildup may occur and cause the trigger to stick.
Apply a high grade, light machine oil to the throttle pivot area, if the trigger is sticking but cleaning didn't rectify the issue. This should be done periodically to keep the trigger well-lubricated and working properly.
Remove the pin that holds the trigger in place so you can replace the trigger, if it is damaged. Each air ratchet make and model is different, so removing the pin may vary slightly. Typically, the pin is removed with a screwdriver or Allen wrench in a counterclockwise direction. There may be a special tool from the manufacturer used to remove the pin.
Order a new trigger from the air ratchet manufacturer. Insert the new trigger, and replace the pin in a clockwise fashion until snug or according to the manufacturer's instructions.