Ventless, or ductless, range hoods are generally safe, as they use filters to remove the heat, smoke and grease particles that are created during cooking. However, this type of range hood system does require regular charcoal filter replacement to ensure that the smoke it absorbs is cleaned.
As of 2015, a typical ventless range hood can only filter out certain types of particles from cooking smoke. Additionally, as this system does not vent air outside of the kitchen, any excess heat and moisture are generally released into the kitchen again. In general, a ventless range hood is also cheaper when compared to a ducted range hood.