What is the least cfm allowed for an intermittent exhaust in a residential bathroom?

The minimum required airflow for an intermittent exhaust fan in a residential bathroom is typically established to ensure adequate ventilation and effective removal of moisture and odors. A rating of 50 cubic feet per minute (cfm) is deemed sufficient as it balances the need for adequate air exchange while being practical for effective operation in most bathroom sizes.

Ventilation standards, such as those set by building codes or health organizations, generally recommend that exhaust fans should have the capacity to handle typical bathroom moisture generated from activities like showering or bathing. The 50 cfm specification reflects an understanding of the average conditions in residential bathrooms, making it a widely accepted standard for achieving effective moisture control and improving air quality.

Values below this minimum often do not provide enough airflow to properly ventilate a bathroom, potentially leading to issues like mold growth and improper humidity levels. Therefore, the choice of 50 cfm aligns with best practices for ensuring a healthy indoor environment in residential settings.