Stuffy homes are unhealthy homes, while homes with plenty of fresh air are healthy. That’s been a commonly held belief for at least 200 years. In the mid-19th century, the connection between ventilation and human health was championed by sanitarians, a group of health experts who blamed the spread of bubonic plague and cholera on “miasma.”According to Michelle Murphy, the author of Sick Building Syndrome and the Problem of Uncertainty, “Ventilation engineers had previously promoted the mechanical supply of ‘fresh air’ in the name of healthfulness, not comfort. The fight against foul air, excess carbon dioxide, and miasma … had allied ventilation engineers with public health reformers, called sanitarians, who sought to improve the living conditions of the worthy laboring poor by … legislating standards for fresh air in tenements, schools, and factories.”The miasma theory of contagion was disproved in the 1860s. However, the connection between ventilation and human health is still trumpeted by various organizations, including “healthy house” groups and fan manufacturers. For example, marketing materials from Broan, a fan manufacturer, claim that “microbial pollutants like mold, pet dander and plant pollen along with chemicals such as radon and volatile organic compounds (VOCs) create a toxic environment in your home.”Similarly, a document posted on the website of the Healthy House Institute declares, “Ventilation is a critical component for home durability and occupant health.”Since experts have posited a connection between mechanical ventilation in homes and human health for the last 160 years, perhaps it’s time to ask two questions:The answer to the first question is no, not really. And the answer to the second question is an emphatic no.The standard for residential ventilation in the U.S. is ASHRAE 62.2. Among the members of the committee that developed ASHRAE 62.2 were Joseph Lstiburek, a principal of… This article is only available to GBA Prime Members Start Free Trial Already a member? Log in Sign up for a free trial and get instant access to this article as well as GBA’s complete library of premium articles and construction details.