This is the twelfth article in our special series to commemorate a century of innovation in the HVAC&R arts and sciences.

In the October issue of ASHRAE Journal, John E. Janssen provides a history of research and standards development aimed at improving indoor air quality. That article reveals that such activities are at least as old as civilization. Now at the brink of a new millenium, it is a good time to take stock as to where we are and what may lie ahead in our quest for better air and in our understanding the influence air quality has upon the complete indoor environment.