Proven Proficiency: Demonstrated proficiency and competence in diagnosing, repairing, installing, and maintaining HVAC, plumbing, and electrical systems, as evidenced by a skill-based pre-employment exam. Qualifications: Demonstrated proficiency and competence diagnosing, repairing, installing, and maintaining HVAC, plumbing, and electrical systems, as evidenced by a skill-based pre-employment exam.