Section 410.220 - Natural and Mechanical Ventilation(A) Habitable rooms, and rooms with a toilet, bathtub or shower shall have: (1) Windows, skylights, or doors through the exterior walls or roofs that can be easily opened with a combined opening of at least 4% of the floor area of that habitable room or room containing a toilet, bathtub or shower; or(2) Mechanical ventilation capable of exhausting air to the outdoors.(B) When the board of health has determined that natural ventilation is insufficient to remove excess moisture, mechanical ventilation is required.(C) Mechanical ventilation shall be installed and maintained in accordance with 780 CMR: Massachusetts State Building Code.(D) Each mechanical ventilation system shall be equipped with a readily accessible means for shut-off, unless such system is designed to run constantly or is barometrically controlled.Adopted by Mass Register Issue 1495, eff. 5/12/2023.Amended by Mass Register Issue 1497, eff. 5/12/2023.