Gas-phase air cleaners are used to remove a wide variety of contaminants from the air. However, it is often difficult to judge which air cleaner works for which contaminants and, further, to determine which air cleaner is best for a given application. Most gas-phase air cleaners use sorbents (eg, activated carbon) to remove the contaminants from the air. Since sorbents vary in which contaminants they can remove and air cleaners contain different sorbents in various configurations, it is critical to have test data to document the performance of air cleaners. To meet this need, ASHRAE has published a new laboratory test standard giving the HVAC market its first gas-phase test standard for air cleaning devices. The air cleaners were chosen to cover a wide range of the capabilities of currently available devices, and include two residential and three commercial units. All of the air cleaners are sorbent-based, but the sorbents are designed to apply best to different contaminants.