You don't want "heritage" from former owners
If your new home had a former owner, most likely you know little about his or her life habits. Were there any pets in the house? Has a house been ever inspected? Has there ever been a mold source found? If you care about air quality, better get an inspection to know what you will have to deal with.
The first step is to keep windows open for several hours and use a disinfector. If the former owner suffered from any disease, sneezed and coughed everywhere, germs and bacteria probably remained in the air.
The second step is to clean your ducts.