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

Air filtration

Air quality is subject to variability due to weather, dust, traffic and localized pollutant sources. Seasonal variations in pollen can trigger asthma and allergies in sensitive individuals. Similarly, exposure to high levels of coarse and fine particulate matter introduced from the outside can lead to respiratory irritation and has been associated with increases in lung cancer as well as cardiovascular disease and mortality. Carbon filters are designed to absorb such volatile pollutants and remove the largest particles, while media filters are meant to address smaller particles.

Part 1: Filter Accommodation

If recirculated air is used, the following requirements are met in ventilation assemblies in the main air ducts for recirculated air:

a. Rack space and fan capacity is in place for future carbon filters or combination particle/carbon filters.
b. The mechanical system is sized to accommodate the additional filters.
Part 2: Particle Filtration

One of the following requirements is met:

a.1 MERV 13 (or higher) media filters are used in the ventilation system to filter outdoor air.
b. Project demonstrates that for 95% of all hours in a calendar year, ambient outdoor PM₁₀ and PM₂.₅ levels measured within 1.6 km [1 mi] of the building are below the limits set in the WELL Air Quality Standards feature.
Part 3: Air Filtration Maintenance

To verify that the filtration system continues to operate as designed, projects must annually provide IWBI with:

a. Records of air filtration maintenance, including evidence that filters have been properly maintained as per the manufacturer's recommendations.

Applicability Matrix

Core & Shell New & Existing Buildings New & Existing Interiors
Part 1: Filter Accommodation P P P
Part 2: Particle Filtration P P P
Part 3: Air Filtration Maintenance P P P
Commercial Kitchen Education Multifamily Residential Restaurant Retail
Part 1: Filter Accommodation P P P P P
Part 2: Particle Filtration P P P P P
Part 3: Air Filtration Maintenance P P P P P

Verification Methods Matrix

Letters of Assurance Annotated Documents On-Site Checks
Part 1: Filter Accommodation MEP Spot Check
Part 2: Particle Filtration MEP Spot Check
Part 3: Air Filtration Maintenance Operations Schedule

U.S. Green Building Council. LEED v4: Reference Guide for Building Design and Construction. Washington D.C.: U.S. Green Building Council; 2013: 37, 43-44, 541-552, 567, 605, 623, 645-53, 658-61, 682-3, 685-6, 723-4.


USGBC's LEED v4 EQ Credit: Enhanced Indoor Air Quality Strategies requires ventilation systems for outdoor air with particle filters to have a MERV of 13 or higher or Class F7 or higher (CEN Standard EN 779-2002) particle air filters.