I don't work in Human Resources but work with them directly on a daily basis. HR is a very diverse group that covers many disciplines. Ours is broken up into a Health care group, employee training group and employee relations. Beside their daily responsibilities they serve on committees and put together all of our corporate functions. The group has a VP of HR, a senior level manger for each section and departmental mangers inside the employee relations group. Several have went on to receive certification.
There is a certification agency for human resources specialist that is broken into three levels at http://www.hrci.org/Certification/OV/
You can apply for certification after working in the field for at least two years in an exempt position according to the web site.
Hope this helps and good luck in your career change.