Cal. Civ. Code § 410.220
Natural and Mechanical Ventilation
Operative Text
(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.Section 410.220 of the Massachusetts Minimum Standards of Fitness for Human Habitation requires that habitable rooms and rooms containing a toilet, bathtub, or shower have either openable windows, skylights, or exterior doors totaling at least 4% of the floor area, or a mechanical ventilation system that exhausts air to the outside. If a local board of health finds that natural ventilation is not adequate to control excess moisture, mechanical ventilation becomes mandatory. Any mechanical ventilation system must be installed and maintained in line with the Massachusetts State Building Code and must include an accessible shut-off switch, unless the system is designed to run continuously or is barometrically controlled.
Plain English — not legal advice.
Under § 410.220, compliant operators ensure that every habitable room and every bathroom in their rental units meets the minimum ventilation threshold — either through openable windows or skylights covering at least 4% of the floor area, or through a properly installed mechanical exhaust system. Landlords generally keep mechanical ventilation equipment in good working order and in compliance with 780 CMR, the Massachusetts State Building Code, and make sure each system has an accessible shut-off control where required. If a local board of health issues a determination that natural ventilation is insufficient to address moisture problems in a unit, operators subject to § 410.220 are expected to install mechanical ventilation in response.
General guidance for property managers — not legal advice for your specific situation. Consult an attorney for advice on your case.
Section 410.220 establishes a baseline right for tenants to have adequate ventilation in living spaces and bathrooms, either through openable windows or a working mechanical exhaust system. If a tenant believes their unit lacks the required ventilation — for example, windows that cannot be opened or a broken exhaust fan — they may consider contacting their local board of health, which has authority under this provision to inspect conditions and require corrective action. Tenants can also reach out to a local tenant-rights organization to understand how a violation of § 410.220 might be raised in a housing court proceeding or used as a basis for a formal complaint.
General guidance for tenants — not legal advice for your specific situation. Consult a tenant-rights organization or attorney for advice on your case.
Generated September 30, 2026 — auto-generated, not yet human-reviewed. See /transparency for methodology.
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