When you hang your clothes and linens outside to dry, there is a reason your sense of smell enjoys the result: there is a scientific chemical process that happens. According to this site, a study shows that towels that dried in the sun produced a range of aldehydes and ketones – organic compounds that our noses associate with the scent of plants or perfume. Line-dried towels emitted pentanal, a compound found in cardamom; octanal, which emits citrus-like aromas; and nonanal, which has a rose-like odor. Your dryer sheets can’t come close.