Kitchen hoods are broadly classified into ducted hoods and ductless hoods. The primary disadvantage of ductless air conditioners is their cost. Two main types exist, ducted and recirculating (ductless). Their products include window, thru-the-wall, portable and ductless air conditioners, as well as dehumidifiers. Therefore, endocrine glands are regarded as ductless glands. Like ductless minisplits, VRFs use refrigerant as the cooling and heating medium. Endocrine glands are termed as ductless and release their secretions directly into the blood. In addition, ductless systems offer higher efficiency, reaching above 30 SEER. There are variations that allow for split systems, high-velocity systems, and ductless systems. An expert said that he might have a "deranged ductless gland". Ductless kitchen hoods do not have a duct that is used to process the air.