The Controlled Descent Apparatus (CDA), or more commonly referred to, as a boatswain chair is one of the most common types of equipment employed for exterior building maintenance.
Cal-OSHA Ruling on Suspended Scaffold System
Chairs are considered conventional equipment supplied by the window cleaning. A controlled descent apparatus is primarily intended to allow downward movement only.
The Controlled Descent Apparatus is the mechanism that allows the window cleaning technician to descend downward in a safe manner.
Independent Anchorages Required
When using a boatswain chair, you must have two lines secured to approved independent anchorages. The boatswain chair line, or “suspension line” is secured to one anchorage, and the “safety” or “lifeline” is secured to another anchorage. The chair is rigged directly to roof in line with the point of suspension, and the primary synthetic rope suspension lines are normally protected at the roof edge using contractor supplied carpet or other anti-protection devices. Alternatively, contractor supplied equipment such as outrigger beams with counterweights, parapet wall clamps or cornice hooks can be used to suspend the chair if they are approved. These devices must be tied back to permanently installed safety anchors.
Note: When the roof edge is not capable of supporting the applied loads, primary suspension support equipment such as outriggers supported on blocks or beam dollies, or davits, must be considered. A separate independent wall or roof anchor is required to secure the worker’s lifeline.
Cal-OSHA Ruling on Controlled Descent Apparatus’ (CDA)
When using such equipment for window cleaning applications, its design, use and maintenance shall conform to Cal-OSHA ruling,
Article 5, §3286. Cal-OSHA expects employers whose employees use descent control devices to implement the following procedures and precautions:
-Have documentation on file that employees have been trained by a competent person
-Review with employees of the written detailed work procedures for the work site provided by the building owner.
-Inspection each day before use of all equipment.
-Proper rigging, procedures utilized.
-Use of separate fall arrest system, which will quickly stop the employee’s fall.
-Ropes are effectively padded where they contact surfaces, which might cut or weaken the rope.
-While suspended, window cleaners shall not reach further than six (6) feet in any direction.
On October 25, 2001, the American National Standards Institute (ANSI) approved the International Window Cleaning
Association (IWCA) I-14.1 Window Cleaning Safety Standard for publication as ANSI/IWCA I-14.1-2001. This standard addresses the safe use of descent control equipment i.e. rope descent systems (RDS) shall not exceed 130’-0” (40 m) above grade unless the windows cannot be safely and practically accessed by other means.
When performing descents over 130 feet (40 m), special attention shall be given to prevent against dangers associated with wind, length of time workers are suspended, the ability of the rope descent apparatus to function without the worker to apply excessive force and the ability to provide a prompt rescue in the event of an emergency. Additionally, in California, special written permission from Cal-OSHA is required for descents over 130 feet (40 m).