This is a legacy version of the WELL Building Standard. Please check the latest version here.

Direct source ventilation

Direct source ventilation


To preserve air quality in occupied spaces through the isolation and proper ventilation of indoor pollution sources and chemical storage areas.


Air pollution can be created from a number of indoor sources, including cleaning products, office equipment and humid environments. Chemical storage closets can be a source of harmful vapors, including VOCs that are linked to cancer, organ and central nervous system damage. Copy rooms can contribute to the production of ozone, which is linked to asthma and other respiratory diseases. Bathrooms can be a source of mold and mildew that release spores and toxins, which can trigger asthma and allergies in susceptible individuals.

Part 1
Pollution Isolation and Exhaust

All cleaning and chemical storage units, all bathrooms, and all rooms that contain printers and copiers (except those meeting the low-emission criteria of Ecologo CCD 035, Blue Angel RAL-UZ 171, or Green Star) meet the following conditions:
Are closed from adjacent spaces with self-closing doors.
Air is exhausted so that all air is expelled rather than recirculated.

Part 2
Exhaust Hood Design Guidelines

The following requirements are met:
Canopy hoods have side or partial panels, when allowable by code.
Type II hood overhangs and setbacks comply with ASHRAE 154-2011 (Table 3 - Minimum Overhang Requirements for Type II Hoods) on all open sides, measured in the horizontal plane from the inside edge of the hood to the edge of the top horizontal surface of the appliance.
The vertical distance between the front lower lip of the hood and cooking surface is less than or equal to 1.2 m [4 ft].

Part 3
Makeup Air System Design

The following requirements are met:
Makeup air velocity near (or directed at) the hood is less than 0.25 m/s [75 fpm].
Replacement air introduced directly into the exhaust hood cavity does not exceed 10% of the hood exhaust airflow rate.
At least 50% of the air that replaces the exhaust air is conditioned transfer air rather than make up air.

Part 4
Appliance Guidelines

The following requirements are met:
Appliances are grouped under exhaust hoods according to effluent productions and associated ventilation requirements, as specified in ASHRAE Standard 154-2011 per hood type (defined by the classifications used in ASHRAE Standard 154-2011 for light, medium, heavy and extra-heavy appliance duty levels).
Appliances have a rear seal between the appliance and the wall, when allowable by code.
Appliances located at the end of a cook line requiring exhaust airflow rates greater than 460 L/s/m [300 cfm/ft], have a full side panel or an end wall.

Part 5
Locker Rooms

Locker rooms, if present, must be ventilated in the following manner:
The return air is vented outdoors and not recirculated.
The ventilation rate is at least 1.33 Air Changes per Hour (ACH).