This Standard provides for the safe design of powered platforms for building maintenance, where window cleaning and related services are accomplished by means of suspended equipment at heights in excess of 35 ft (11 m) above a safe surface, e.g., grade, street, floor, or roof level.

The provisions of the Standard are intended to apply to all known systems used to support suspended maintenance equipment as well as the suspended equipment itself (either permanently installed or transportable equipment). Guidelines are also included for a building’s structural support areas as well as the building surfaces that actually interface with the equipment.

The Standard does not apply to other suspended powered platforms used for remedial renovations or modifications to buildings. The safe use of these types of scaffolds is addressed by American National Standard ANSI A10.8. The A120.1 Standard also does not relate to any service performed by persons supported by equipment covered by any of the ANSI A92 standards. The purpose of this Standard is to ensure the protection of all powered platform users as well as persons potentially exposed to use of the equipment. In developing this Standard, safety has been held as the primary consideration. The Standard requires that permanently installed or transportable equipment be properly designed by a qualified professional engineer, taking into account specific building features rather than attempting to accommodate the system to a building’s structure and facade features that may not be suitable for its safe operation. In addition, care has been taken so as not to exclude or render obsolete any existing product or equipment.

This Standard reflects the evolution of a project begun in 1962 by the American National Standards Committee on Window Cleaning Safety, A39. At that time, the Committee recognized that a new method was being developed for cleaning fixed sash windows by means of a special scaffolding. In order to deal expertly with this new development, a new project was established, separate from that handled by the A39 Committee. Following a general conference, the American National Standards Committee on Powered Platforms, ANSI A120, was formed, with the National Safety Council acknowledged as sponsor. In 1965, The American Society of Mechanical Engineers was approved as cosponsor. In 1984, the Building Owners and Managers Association International was approved as Secretariat.

A previous edition of the Standard, A120.1-1970, was administratively withdrawn in 1989. This Standard had established safety requirements for the design, construction, installation, inspection, and use of power-operated platforms for exterior building maintenance. The Standard did not apply to temporary equipment used for construction work or to devices raised and lowered manually.

A120.1-1992 was the result of joint action by participating organizations under the auspices of the American National Standards Institute. That Standard was approved through two votes of the ANSI A120 Committee, at a meeting in New York City (October 17, 1991) and by letter ballot (dated December 30, 1991).

In 1995, ASME again assumed sponsorship of the Standard. ASME A120.1-1996 was approved by ANSI on April 17, 1996. ASME A120.1-2001 was approved by ANSI on July 3, 2001. ASME A120.1-2006 was approved by ANSI on September 20, 2006.

This revision was approved by the American National Standards Institute on July 16, 2008.