The National Air Duct Cleaners Association (NADCA) is recognized today as the premier standard setting organization in the world, in the field of HVAC system cleaning. In 1995, NADCA created a program to certify professionals in the air duct cleaning field. Individuals who pass the NADCA certification examination are designated certified "Air System Cleaning Specialists" (ASCS). The NADCA website provides information regarding what is required for NADCA certification. Those who pass the ASCS exam must also sign a NADCA Code of Ethics, which in essence, verifies that each NADCA certified ASCS maintains a high level of ethical behavior and professional performance. The ASCS pledges that he will at minimum, clean all air duct systems to industry performance standards established by NADCA. These standards require that all interior surfaces of the air duct system be cleaned, from the point where air enter the system, downstream to where it exits the system at the registers, and this includes the air conditioner and furnace.