Yes, range hoods can be operated without an exhaust duct by using a ductless or recirculating range hood. These types of range hoods use filters to capture grease and odors, and then recirculate the air back into the kitchen. While they are not as effective as ducted range hoods at removing cooking byproducts from the air, they can still help improve indoor air quality and reduce odors in the kitchen. However, it's important to regularly clean and replace the filters in a ductless range hood to maintain its effectiveness. **