If you work on a roof, power poles, tree trimming, cell towers or any other location, you should be aware of an additional risk you face, above and beyond the immediate risk of a fall. The technical name is orthostatic intolerance, and in some conditions it can kill a person hanging in a harness in 30 minutes or less.
When you don’t move your legs in a standing position, blood pools in the legs, which is called “venous pooling.” Gravity pulls the blood away from the heart and brain, and the lack of movement in the legs inhibits muscle movement that typically assists in moving the blood back to the upper body.
This is why people standing for long times can faint. For someone in a body harness, who has fallen, there is a risk that they could suffer orthostatic intolerance after their fall has been arrested, but while they are awaiting rescue.
If you work in conditions where this could occur, rescue procedures should be in place that could effectuate a rescue immediately. And workers who are exposed to this risk should be trained in how to respond.
If they cannot be brought up or lowered to the ground as soon as the fall has occurred, they should be instructed to constantly move their legs while they are suspended, if possible. If they are unconscious, it becomes critical that they are rescued with little delay, as leaving them suspended could lead to life-threatening conditions.
Rescue teams must also be aware that they are at risk if they must hang suspending for extended periods during a rescue.
Source: osha.gov, “Suspension Trauma/Orthostatic Intolerance,” Occupational Safety & Health Administration, SHIB 03-24-2004, updated 2011.