Clean air is a critical component to our health. Air pollution is the number one environmental cause of premature mortality, contributing to 50,000 premature deaths annually in the United States and approximately 7 million, or one in eight premature deaths worldwide.

Globally, outdoor air quality is deteriorating due to pollution from traffic, construction, agricultural activity, combustion sources and particulate matter. Because ambient air diffuses easily, even distant sources of pollution have a huge impact on the more than 15,000 liters of air we breathe every day. Indoor air quality can be degraded by these outdoor sources, as well as by off-gassing from building materials, indoor combustion sources and water leaks. Poor ventilation practices can fail to address these sources, exposing us to volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs) and microbial pathogens. Another way in which indoor air quality may be diminished is via surfaces, which can accumulate airborne germs. All of these contaminants contribute to a range of negative health outcomes such as asthma, allergies and other upper respiratory illnesses. In addition, air quality issues can diminish work productivity and lead to sick building syndrome (SBS), where no disease or cause can be identified, yet acute health effects are linked to time spent in a building. SBS symptoms include various nonspecific symptoms such as eye, skin and airway irritation, as well as headache and fatigue.

The reactions people have to air pollutants vary widely and depend on multiple factors including the concentration of the contaminant, the rate of intake and the duration of exposure. Pollution source avoidance, proper ventilation and air filtration are some of the most effective means of achieving high indoor air quality. In the U.S., the Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS) according to ongoing research and monitoring. These Standards have been credited with dramatic improvements in outdoor air quality, and create exposure limits based on both duration of exposure and concentration for the six major air pollutants: carbon monoxide (CO), lead (Pb), nitrogen dioxide (NO₂), ozone (O₃), particulate matter (PM₁₀ and PM₂.₅) and sulfur dioxide (SO₂). The WELL Building Standard® expands upon these requirements by incorporating standards from additional agencies, such as the World Health Organization (WHO). To help minimize transmission through contact with unsanitary surfaces, the WELL Building Standard provides an approach that combines the installation of appropriate materials with the implementation of effective protocols to regularly disinfect targeted areas.

In addition to limiting pollutant and contaminant concentrations, WELL incorporates best practices from industry organizations, whose guidelines are evidence-based and recommended by professionals. One such group is the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), which regularly updates its building handbook to include new techniques for enhancing air quality within buildings. Although ASHRAE is a technical society without a legal mandate, many state and local governments have modeled their codes based on ASHRAE’s standards. In addition, the U.S. Green Building Council's LEED® program continues to set new standards for both air filtration and building material selection to improve air quality.