Warm air furnaces (also known as forced-air furnaces) were regulated for the first time by the U.S. Environmental Protection Agency (EPA) with new regulations finalized in February 2015.
- Smaller-sized furnaces (those under 60,000 BTUs) had an effective date of May 15, 2016 (one year after the regulation was finalized).
- Larger furnaces (those equal to or greater than 60,000 BTUs) had an effective date of May 15, 2017.
EPA recognized that, since these were new regulations, manufacturers needed time to review the new requirements and develop products that meet the standards.
Today, all warm air furnaces are EPA-certified to the Step 1 requirements that came into effect in 2016 and 2017. 
View the list of EPA-certified warm air furnaces