Ductless hoods are one option that some restaurant owners may choose to consider. Like the Type 1 and Type 2 commercial hoods, ductless hoods will remove contaminants from the cooking area in the kitchen. The main difference is that the ductless hoods will clean and filter the air but then return it to the kitchen area, rather than directing it to the outdoors. While directing the contaminated air to the outdoors is the ideal solution to commercial kitchen ventilation, ductless vents are often the only option for certain kitchen designs and may be appropriate.
When choosing to use a ductless commercial hood in a restaurant kitchen, certain conditions should be explored carefully to ensure that the ductless hood is safe for the particular situation. Ductless hoods do tend to be less effective at fully cleaning the contaminated air and should therefore be generally avoided in high volume restaurant kitchens.
All commercial and restaurant kitchens require adequate ventilation, and a ductless hood is certainly a better choice than no hood at all (which would not only lead to unsafe and unsanitary conditions, but health and fire code violations as well).
Any time that a ductless hood is used in a restaurant kitchen, the filters should be regularly inspected and either completely cleaned or replaced, depending on the particular type of filter that is used. Filters must be very effective, as they are removing contaminants and allowing the filtered air to be recirculated.
Having too many contaminants recirculated can lead to dangerous conditions. Because there is no ductwork and the air does not actually leave the kitchen area, it must be cleaned as much as possible.
Typically, ductless commercial hoods use charcoal filters that must be periodically replaced and cannot be cleaned. Replacement frequency depends somewhat on the volume of usage in the kitchen.
Generally speaking, ductless commercial hoods are less desirable than the standard type of vented commercial hood, but they are often adequate for smaller kitchens that may not be properly equipped for more elaborate commercial kitchen ventilation systems.