"Avoid oversized range fans, which can depressurize homes and cause back-drafting of combustion appliances. For most kitchen applications, a range hood fan with a capacity of ~200 CFM is more than adequate." change to "Avoid oversized range fans, which can depressurize homes, cause back-drafting of combustion appliances and fireplaces, and lead to higher energy bills. For most kitchen applications, a range hood fan that is sized to meet the requirements in ASHRAE Std. 62.2 will suffice."