Buyers Guide: Descent-Control Devices Descent-control devices (or descenders) provide workers-at-height a means to descend at a controlled rate. Specific hands-on training is required for use of all descent-control devices. This article gives a brief overview of the descenders commonly used by modern professionals along with some thoughts based on our own experience. Descenders employ the concept of friction to control the rate of descent. Most descenders can be used for either lowering or rappelling (abseiling). Technicians rappel by using the descender as a traveling brake to control their own rate of descent. Technicians can also lower personnel and loads by operating the descender as a fixed brake attached to an anchor.

Descenders used in most industrial work applications should be outfitted with a self-braking mechanism that engages if the operator lets go of the device. This self-braking mechanism is integral to the device (e.g. Petzl Stop or I'D) or can be added by the user in form of a mechanical or rope prusik when using a rappel rack or figure 8. An independent back-up safety system should be used during most rope-supported activities. A method of reversing the descent operation (ascending or raising) should be available in case of unexpected complications.

While there are numerous descenders used world-wide for rope access and rescue applications, we profile some of the most commonly-used devices: the Petzl Stop, Petzl I'D, Fisk Descender, Petzl Gri Gri, Petzl Rappel rack, Petzl Huit (Figure 8), and RA/SMC (Rescue 8).

Petzl STOP MSRP: $85. Tech Notice Weight: 326g		The Petzl Stop is the most-commonly used device in rope access applications because it is lightweight, reliable, easy to inspect, and reasonably priced. Originally developed for caving, the Stop has a long track record of reliable performance in rope access operations. The Stop is often compared to the Petzl I'D as they are both equipped with a self-braking mechanism. However, the Stop doesn't quite stop. It creeps and must be tied off while working or negotiating obstacles. The Stop does operate smoothly on a variety of terrain from low angle to vertical. Unlike the I'D, the Stop doesn't function well as a progress capture device, belay device, or ascender. It isn't outfitted with a panic lock, positive locking mechanism, or lock if threaded backwards. In other words, only experienced and well-trained users with appropriate supervision should be trusted with the Stop. The Stop will wear out under extreme conditions and is not recommended for routine use on long descents (over 100 m). While we generally prefer the I'D, the Stop is definitely a good piece of gear. There are some applications that the Stop may be the best tool for the job, especially on lower angle descents. For many of the reasons mentioned above, the Stop will continue to be the work-horse of choice for many rope access companies.
Petzl I'D MSRP: $185. Tech Notice Weight: 1.2 lbs.		The I'D is our descender of choice for most rope access and industrial applications because of its versatility and safety features. It can be used as a progress capture device, belay device, and ascender. It's safety features include a positive locking mechanism, a self-braking mechanism that really stops, a panic lock if the user pulls back on the lever too hard, and an anti-idiot mechanism if it is loaded backwards, which is done commonly. There are 2 sizes that cover a variety of rope diameters. Some of the disadvantages of the I'D include that it is more expensive and a bit heavier than the Petzl Stop, it is impossible to inspect all the parts in the field, and it doesn't operate well on long descents (over 100 m) or on low angle slopes. The I'D has been operating reliably within our rope access and rescue operations for about 5 years. As with all technical equipment, proper training is essential. Note: Petzl is working on an even stronger model of the I'D that will not have the latch on the clam shell. The goal is to have an NFPA G-rated device. This will unfortunately come at the expense of the latch which is quite useful for rope access work.
Petzl Gri Gri MSRP: $79.95 Tech Notice Weight: 7.9 oz		The Gri Gri, the predecessor to the Petzl I'D (Industrial Descender), was originally designed as a belay device for the recreational climbing market. The most appropriate use of the Gri Gri in the industrial market is as a work positioning device and as a descender for low-angle slopes or any application where the full weight of the technician is not on the device. The I'D does not excel in this environment because the panic lock engages too easily when not fully loaded. While the Gri Gri has a self-braking mechanism, it does not have a positive lock, panic lock, or error capture device if it is loaded backwards. There is a risk of dropping it because it must be removed from the carabiner when not in use. The Gri Gri can only be used on rope diameters of about 10-11 mm (appx 3/8"-7/16"). We do not recommend using the Gri Gri as a primary descender because of the lack of safety features mentioned above and it is not very smooth under fully loaded conditions. However, in certain work-positioning and low-angle applications, it is the best tool for the job.
Brake Bar Rack MSRP: $92.50 Tech Notice Weight: 1.15 lbs.		The Brake Bar Rack is a very durable, smooth, and reliable lowering and rappel device commonly used by technical rescuers, window cleaners, and cavers. While it is considerably heavier and bulkier than most descenders used in industrial rope access, the main advantage is that the number of bars can be changed to alter the amount of friction required by various rope diameters, pitch lengths, load weights, and slope angles. The steel rappel bars are very durable for extreme use, long descents (100+ meters), gritty ropes, or constant and repetitive use. It does not have a self-braking or locking mechanism and it can not serve as a progress capture, ascender or belay device. While we don't recommend the rack for complicated rope access maneuvers, it is our device of choice for big descents (e.g. face of Glen Canyon Dam) and routine high-rise maintenance (e.g. window cleaning).
Figure 8 & Rescue 8 (Petzl Huit Antibrulure and SMC Rescue 8) MSRP: $22 & $40.85 Tech Notice Weight: 3.9 & 6.5 oz		The Standard 8 and the Rescue 8 are used commonly in recreational applications as well as tactical operations. The rescue 8 has additional ears to assist with tying off the device. While we see Figure 8's used in rescue and industrial applications we believe there are better tools for the job. The main advantage of the figure 8 is that it is lightweight, inexpensive, and relatively easy to use. The figure 8 and the Fisk descender twist ropes considerably which can be a hassle. The other disadvantages include: no self-braking mechanism; doesn't dissipate heat well on longer descents; and difficult to tie off (standard 8).
Alpine Brake Tube (Petzl Tuba) MSRP: $170 Tech Notice Weight: 43.7oz		The Alpine Brake Tube is a specialized lowering device that has the ability to conveniently pass knots through it. It is generally not recommended as a rappel device. The amount of friction applied to the system can be changed easily with the number of wraps around the tube. It has no self-braking mechanism and is the largest and heaviest lowering device reviewed.
Fisk Descender MSRP:$155 Tech Notice Weight: 1.8 lbs.		We haven't logged many hours on the Fisk Descender. From our perspective, it is an antiquated device even though it is still commonly used in tower rescue applications. It provides more friction and dissipates heat better than the figure 8 for two-person loads, however, it is unnecessarily complicated, twists ropes like crazy, and is a bit heavy for what it does. It doesn't have a self-braking mechanism, but, it is relatively easy to tie it off. While we can sell you a Fisk descender, we will probably try to talk you into upgrading to an I'D.