Underwriters Laboratories, Inc. (UL) is an agency that lists products they have tested against criteria deemed appropriate for public safety. The classifi cation for HVAC air filters confirms that the filters will meet local and state requirements for most applications.
UL 900 covers both washable and throwaway filters, used for the removal of dust and other airborne particles from mechanically circulated air in equipment and systems. This is in accordance with the Standards of the National Fire Protection Association (NFPA) for Installation of Air Conditioning and Ventilating Systems, of Other Than Residence Type, NFPA No. 90A, and for Installation of Residence Type Warm Air Heating and Air Conditioning Systems, NFPA No. 90B.
After a period of service, the combustibility and smoke generation of an air filter will depend upon the nature and quantity of the material collected by the filter. The test requirements of this Standard, for classification purposes, applies only to air filters in a clean condition.
A UL 900 Classified Filter is an air filter which, when clean, will burn moderately when attacked by flame, or emit moderate amounts of smoke, or both. The air filter unit shall not produce flame or extensive sparks, which are sustained beyond the discharge end of the test duct described in the Standard, when subjected to the flame exposure test. In addition, the burn shall not cause the development of an area of more than 9 square inches as measured below the smoke-density time curve.
Additionally, the adhesive material used for coating the filtering media, or other parts of an air filter unit, shall have a fl ash point of not less than 325 degrees F, Cleveland Open-Cup Method ASTM D92-5a (ANSI Z11.6- 1966).
It is important to note that the toxicity of the products of combustion, resulting from a filters exposure to flame, is outside the scope of UL 900, as is the filter’s particle capture efficiency before or after flame exposure.
To obtain a UL listing for a product, an application is made to Underwriters Laboratories and several samples are then submitted for testing. All of these samples must successfully pass the criteria established for the Standard.
A listing is then granted only if the manufacturer further agrees to a followup service procedure. In this procedure, a UL representative visits each point of manufacture quarterly, and selects a random sample for annual testing. This sample is returned to UL for retest to assure continued compliance with the appropriate test criteria.
For Camfil, UL periodically selects samples from our Riverdale, NJ, Corcoran, CA, Crystal Lake, IL, Conover, NC, France, Germany, Malaysia and China facilities.
Only products which meet the criteria for listing may use the UL label. Products not required by UL to comply with UL 900, even though they may be similar in appearence, will not bear the UL label. The UL Standard ensures that the end user is receiving a product that meets a specific level of quality, or meets the requirements as published byb the filter’s specifier.
It is important to note that currently, there is only one UL 900 classification for air filters. The decision to sunset the dual-class Standard, Class 1 and Class 2, was made in September of 2009. Manufacturers have until May of 2012 to move into full product labeling conformance with the new marking classification.
A listing of product Certifications, for all manufacturers is available on the UL website at http://www.ul.com, under the menu choice of Online Certifications.