ANSI Standard Z83.18 Recirculating Direct Gas-Fired Industrial Air Heaters, which covers any unit that might use recirculated air for part of its operating range, was substantially revised earlier this year. However, some say the new standard is causing confusion for HVAC engineers and building code authorities.

As of January 1, 2003, manufacturers who wished to abide by the new standard had to make some significant changes to their equipment. They were also required to place more complete information on a unit’s nameplate, including certified capacities, inputs, maximum temperature rise, and discharge temperature.