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

Advanced air purification

Some circumstances justify greater investment in air purification strategies. For example, proximity to highly traveled roads, manufacturing plants and seasonal variation can affect outdoor air quality, increasing ozone and VOC content, and in turn diminishing indoor air quality. Similarly, climates with high humidity levels and inadequate indoor ventilation can foster the development of mold and spores in indoor environments.

This feature requires the use of carbon filters to remove VOCs and ozone, and ultraviolet sanitizers to irradiate any bacteria, viruses and mold spores present in circulating indoor air.

Part 1: Carbon Filtration

To reduce VOCs in the indoor air, buildings which recirculate air use one of the following methods:

a. Activated carbon filters in the main air ducts to filter recirculated air. Replacement is required as recommended by the manufacturer.
b. A standalone air purifier with a carbon filter used in all regularly occupied spaces. Purifiers must be sized appropriately to the spaces they are serving. Filter replacement is required as recommended by the manufacturer.
Part 2: Air Sanitization

Spaces with more than 10 regular occupants, within buildings that recirculate air, use one of the following treatments or technologies to treat the recirculated air, either integrated within the central ventilation system or as a standalone device:

a.15 Ultraviolet germicidal irradiation.
b.15 Photocatalytic oxidation.
Part 3: Air Quality Maintenance

As evidence that the selected filtration/sanitation system chosen continues to be fully operational, projects must annually provide IWBI with:

a. Records of air filtration/sanitization maintenance, including evidence that the filter and/or sanitizer has been properly maintained as per the manufacturer's recommendations.

Applicability Matrix

Core & Shell New & Existing Buildings New & Existing Interiors
Part 1: Carbon Filtration O O O
Part 2: Air Sanitization O O O
Part 3: Air Quality Maintenance O O O
Commercial Kitchen Education Multifamily Residential Restaurant Retail
Part 1: Carbon Filtration O O O O O
Part 2: Air Sanitization O O O O O
Part 3: Air Quality Maintenance O O O O O

Verification Methods Matrix

Letters of Assurance Annotated Documents On-Site Checks
Part 1: Carbon Filtration MEP Spot Check
Part 2: Air Sanitization MEP Spot Check
Part 3: Air Quality Maintenance Operations Schedule

U.S. Environmental Protection Agency. Residential Air Cleaners: A Summary of Available Information. Washington, DC: U.S. Environmental Protection Agency; August 2009.


The EPA's "Residential Air Cleaners" notes that properly designed UVGI cleaners in typical airstream disinfection applications could reduce the viability of vegetative bacteria and molds, and could provide low to moderate reduction in viruses.


The EPA's Residential Air Cleaners document notes that photocatalytic oxidation cleaners are intended to change gaseous pollutants and associated odors into harmless products.