Hitachi brad nailer - firing it empty against a hard surface
Don't dry fire brad nailers against anything you wouldn't drive a nail into. The instructions (PDF) specifically state, "against the workpiece," don't they? Use a scrap piece of wood for the initial testing. You may also want to limit dry firing to initial setup and any future troubleshooting procedures. Many newer nail guns have a dry-fire lockout that prevents the tool from firing when fasteners run out. This is partly to protect a workpiece from being marred by the hammer, and partly to extend the life of the tool.

Why would you test fire it against concrete? You bought a brad nailer, not a Ramset!