Regardless of the scope of your project, find out what you need to do to prepare your home for their visit. For example, the HVAC professional will need access to the areas in question and may need access to other mechanical or ventilation points. Make sure pets and children are kept out of the way. Ask if your project will involve removing dry wall or making any other structural changes – you may need to hire a professional drywall contractor to patch up HVAC work. If you are adding a unit that may contribute to carbon monoxide within the home, find out if you need to purchase a carbon monoxide detector.