Safety Harness Users Beware

Personnel who routinely use safety harnesses may feel that they are doing all the right things and therefore have nothing to worry about while using them. But managers and the technicians they oversee should be alert to a potentially hazardous situation in conjunction with the use of those harnesses.

The purpose of the safety harness is to prevent the wearer from falling from a great height such as the top of the fuselage of an aircraft. Most reputable employers now require these harnesses to be worn while doing work atop an aircraft. But there is a risk that many may not be aware of, not from falling, but from the harness itself. The hazard is called suspension trauma.

Suspension trauma occurs when the person wearing the safety harness has taken a fall, been caught by the harness, and hangs vertically suspended. This situation can be deadly whenever a worker is suspended for a duration of more than five minutes in an upright posture, with the legs relaxed straight beneath the body. According to an article in the Occupational Health & Safety magazine fall-protection researchers have recognized this phenomenon for decades. Unfortunately, users of the equipment have not been made aware of the potential hazard.

Suspension trauma is caused by orthostatic incompetence, a condition that occurs when the legs are immobile, and an upright posture is maintained. Gravity pulls the blood into the lower legs. Legs have a large storage capacity and eventually enough blood accumulates in them that return blood flow to the heart is reduced. The heart tries to compensate by beating faster but is ineffective. This can happen to soldiers who are required to stand at attention for long periods of time. Typically the soldier passes out and the slumping of the body allows the blood to flow and recovery is quick. But for those suspended upright in a harness, that is not the case. The legs are dangling, the harness itself exerts pressure on the leg veins, reducing blood flow, and the harness keeps the worker in the upright position regardless of loss of consciousness. This combination of circumstances can lead to the worker passing out, and death can occur in as little as 15 minutes.

Some guidelines from Occupational Health & Safety for using safety harnesses follow:

• Workers should never work alone in a harness.
• The onset of suspension trauma can be slowed by pushing down forcefully with the legs while suspended.
• Workers should be trained to move their legs in the harness and push against any foothold after a fall.
• Workers should also be trained to get their legs as high as possible and head as close to horizontal as possible.
• Time in suspension should be limited to less than five minutes.
• Ensure the harness user is conscious at all times.
• Workers in the shop should be instructed that a vertically suspended worker could be in a potentially fatal situation.