Insulating duct pipes for range hoods prevents condensation from forming and dripping back into the hood, which can occur when cooler air passes over warm uninsulated ducting. Either applying insulation to the pipes or burying them in existing insulation is appropriate, based on the technology available as of 2015.
Installed range hoods with proper ventilation helps avoid health issues. Carbon monoxide and microparticles of food coated with toxic chemicals escape into the air during cooking. Incomplete combustion of food in gas flames produces nitrogen dioxide, which increases lung inflammation and asthma symptoms, especially in children.
Steps to improve range hood effectiveness include venting to the outdoors if possible, installing the hood within 24 inches of the heating surface, using the back burners and turning the unit on before turning on the stove.