HVAC mechanics and installers work on heating, ventilation, cooling, and refrigeration systems that control the temperature and air quality in buildings. Heating, air conditioning, and refrigeration mechanics and installers typically do the following: Use blueprints or design specifications to install or repair HVACR systems Connect systems to fuel and water supply lines, air ducts, and other components Install electrical wiring and controls and test for proper operation Inspect and maintain customers’ HVACR systems Test individual components to determine necessary repairs Repair or replace worn or defective parts Determine HVACR systems’ energy use and make recommendations to improve efficiency