Fire and life safety dampers manufactured after July 1, 2002 must be tested and qualified to meet new Underwriter’s Laboratory (UL) requirements. Dampers rated to function at 165F, 212F, 250F, 350F, and other elevated temperatures must now be tested at these temperatures. This includes leakage testing, testing to establish airflow velocity and pressure ratings, and fire temperature closure tests. Previously most of this testing was done at room or ambient temperatures. Levels of qualification have been established for airflow velocity and differential pressure. These levels of qualification require testing at higher pressures and velocities to provide a safety factor and ensure reliability. Dampers intended for use in dynamic HVAC systems, which include combination fire smoke dampers, smoke dampers, and dynamic fire dampers, have pressure and velocity qualification levels as follows: • Airflow velocity rating levels of 2,000, 3,000, and 4,000 fpm • Pressure rating levels of 4-, 6-, and 8-in. W.G. Under previous standards, no safety factors, minimum velocity, or pressure rating levels were required. This deficiency has been corrected by the 1999 versions of the standards. All airflow, pressure, and leakage ratings must be established with airflow in both directions through the damper. Previously, these ratings could be established with airflow in only one direction. If the damper was installed backwards, or if airflow reversed during a fire emergency, the damper's ratings were suspect, Cycling requirements have been significantly increased. Dampers must be qualified with specific electric or pneumatic actuators (which must now be furnished as a part of a damper assembly when it is shipped from the factory). Each damper/actuator assembly must complete 20,000 cycles prior to the other testing required by the new standards. Only damper/actuator assemblies that have completed the 20,000 cycles can be used when testing to qualify for temperature, pressure, and airflow ratings. Previously only 5,000 cycles were required and separate (uncycled) damper/actuator assemblies could then be used for other qualification tests. Underwriters Laboratory is an independent, not-for-profit product safety testing and certification organization, first published UL Standard 555 (Fire Dampers) in 1968. UL Standard 555S (Leakage Rated Dampers for Use in Smoke Control Systems), which established requirements for Smoke dampers, was published in 1983. In June 1999, UL 555, Fire Dampers, 6th edition and UL 555S Smoke Dampers, 4th edition were issued. These two UL Standards define the qualifications for all fire dampers and smoke dampers required by building codes in current use throughout the USA. The June 1999 editions also establish specific requirements for combination fire & smoke dampers. Some damper manufacturers already have fire, smoke, and combination fire smoke dampers qualified to the new and upgraded UL Standards. UL listings of all smoke and dynamic fire dampers qualified under earlier versions of these standards will expire as of June 30, 2002. Commencing July 1, 2002, damper manufacturers may not apply UL labels or claim UL listing of smoke and fire dampers unless they have been qualified to the requirements of the June 1999 versions of these UL Standards. To identify products that comply with the latest UL Standards, refer to the UL’s website ( under product category code EMME. The products listed under this code have been tested to comply with the most current requirement.