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More on belay devices... 13-Aug-2003 At 5:11:31 PM dodgy

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As the "Weird ways to get wasted" forum is so random now, here is the (edited) excerpt from "Rock and Ice - Gear" on the loads generated by different devices and techniques:
Sport and gym climbers who usually belay from the ground often become complacent because they have never had to catch a hard fall - fall factors greater than 0.8 can happen only if the leader plummets below the belayer. (Up to factor 1 is theoretically possible, but rope stretch means the climber hits the ground.) Particularly worrisome to traditional climbers is the force placed on the top piece of protection in a hard fall. In one series of tests by REI, most belay devices in a factor 1 fall kept the load on the top piece to about 4.5 kN, while a GriGri averaged over 9.8 kN.
Another test series in Germany showed that a 0.375 factor fall with a 70-kg climber subjects the top piece to about 5.3 kN with a GriGri on the harness, while a Munter yielded 3.8 kN and a figure eight kept it to 3.5 kN. Attaching the belay device to your harness, rather than an anchor, lessens the impact on the climber and anchors. One test showed that forces are reduced from 15 to 30 percent due to the belayer being pulled forward or lifted into the air. If the belayer jumps in the direction of the rope while catching a fall with a GriGri, the peak force on the top piece drops to about 3.4 kN. That's great for sport climbers belaying on the ground. But this technique is next to impossible at a small stance or hanging belay, and the forces allowed by a GriGri should cause serious concern for the many did climbers now using these convenient devices to belay on walls.