Sprinkler fitters are pipe fitters who work specifically in fire protection. These workers install and design overhead sprinkler and hose systems, fire mains, underground systems and underground closed valves. They inspect and test systems, as well as repair defective, worn or broken parts. They may be tasked to perform National Fire Protection Association inspections on buildings or new installations. While most sprinkler fitters are hired by plumbing and heating contractors, the U.S. Bureau of Labor Statistics notes that 11 percent of workers were self-employed in 2012.