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

Microbe and mold control

Microbe and mold control


To reduce mold and bacteria growth within buildings, particularly from water damage or condensation on cooling coils.

Part 1 applies to all cooling coils and drain pans located within the primary air handling unit and any secondary equipment downstream. Note, a combination of UV lights and/or quarterly inspections is acceptable to comply​ with the part. ​

To comply with Part 1 Option b, the Multi-family developer / landlord would need to offer a quarterly inspection to residents at no additional charge. Individual households are free to opt out of this service, and this should be recorded in the maintenance log to demonstrate that effort was made to communicate and extend the inspection offer to residents but that access was denied to complete the checks. The maintenance log, along with photos of successful inspections, still need to be submitted to the IWBI once a year as part of ongoing documentation requirements.

Project teams should calculate the power (irradiance) received by the cooling coils from the ultraviolet lamps to ensure the effectiveness of the system.

Yes, in order to demonstrate compliance with the preventative maintenance plan requirement, photos must be taken during the quarterly inspection. These photos will then need to be submitted to the IWBI once a year as part of the ongoing documentation requirements.

No, a mold inspection will be conducted by the WELL Assessor during the projects Performance Verification.

All air handling units and fan coil units with cooling capabilities must meet either Part 1a (UV systems) or Part 2a (regular inspection and cleaning). Not all units are required to use the same option.

Yes, projects which meet the cleaning and reporting requirements outlined in option b of part 1 are not required to use UV lamps.