How Does a Safety Harness Work?
I recently wrote an article detailing how to ensure you are using your fall protection equipment properly. If you are the inquisitive type, it may have left you asking the question, “How, exactly, does a safety harness work?” In reality, there is a fairly simple answer to this question: distribution of force. But what does that mean and why is it necessary?
Bye Bye Body Belts
To see why it’s necessary, we only need to go back a few years – prior to January 1, 1998 to be exact. For the more seasoned safety professionals among us, this may conjure up an image of a time when fall protection, if worn at all, sometimes consisted of a body belt. Nowadays, the body belt has been banished to the Island of Misfit Toys (or, more accurately, to the role of ‘positioning device only’ [29 CFR 1926.502(d)]) and for good reason. What the body belt accomplished, when the forces exerted on the body in a fall were too great, was to concentrate those forces into a person’s waist, essentially causing them to snap in half. This was not, obviously, the desired outcome of a fall event.
Protect the Vitals
According to OSHA, personal fall arrest systems (PFAS) must limit the maximum arresting force on an employee to 1800 pounds when used with a body harness [29 CFR 1926.502(d)(16)]. The harness then takes these forces and, through its system of straps and buckles, distributes them to the parts of the body best suited to absorb force and support your weight: the large muscles of the upper thighs, chest and shoulders, as well as the bony mass of the pelvis. In doing so, it diverts the forces from the more vulnerable parts of your body: the groin, stomach and neck. Keep in mind, however, that safety harnesses are designed to protect you in a fall and, unlike harnesses such as those used for mountain climbing, are not designed for prolonged suspension. The same technology used to distribute force throughout your body could cut off circulation, leading to suspension trauma.
In addition to distributing force, the design of a full body harness serves to keep an employee upright in a fall. This allows a deceleration device to properly deploy, but also keeps the spine vertical, which is the position in which it can best absorb compressive forces of a fall. Ultimately, this position is the optimal position for rescuing or lowering a worker to a safe location. Even so, this upright position could cause blood to pool in the legs. Upon retrieving a fallen worker, emergency personnel will often lay him or her down. The blood that had been pooled in the legs can, in this situation, rush to the heart causing cardiac arrest. This is why rescue plans are so critical. This potentially fatal result of suspension could occur after as little as 10-20 minutes.
Remember, as I stated in the aforementioned article, none of this matters if the harness isn’t worn properly or does not properly fit the user. Adjust all of the straps and buckles to ensure a snug, but not overly-tight fit. It is important to note that while that the majority of harnesses out there were not designed with women in mind. While a typical harness will do the required job, there are women’s harnesses on the market that do things such as keep shoulder straps to the side of the chest, support the hip and pelvic area different, and/or reduce stress on the lower back. Research the products available to you, and make sure to select the harnesses most appropriate for you or your workforce.