Air fresheners are possibly the worse way to attempt to improve air quality. At best they do nothing positive and at worse they fill the air with dangerous chemicals that may cause respiratory health problems. Air fresheners are only effective at creating an unnatural aroma that disguises the real problem.
If you feel that you need air fresheners because your home smells, think again! What you really need is to locate the source of the bad smells and eliminate them, or treat them directly. Disguising bad smells will worsen indoor air quality, not improve it.
If you need to scent your home use essential oils instead. These natural oils also provide some therapeutic properties that can help you relax and unwind.