By Jordan Hollingsworth, MS, ASP, CHST, CHSP, CRIS®
Safety Advisor, Design and Construction
To children, few things are as thrilling as a jump from a “high” location. We can all remember jumping off of playground equipment, tree limbs, or small hills -- along with the occasional scrapes and bruises we received to remind us of the hazards.
By the time we become adults, the sense of falling takes on a different feeling. Part of that is that we rarely fall deliberately, and the surfaces that break our falls tend to be less forgiving than grassy fields and playground surfaces. Our bones and joints tend to be less forgiving, too. Knowing the physics of a fall underscores the danger: when you fall from just six feet, your body will hit the ground at 13 miles per hour.
Falls are a particular concern to safety professionals, in part because workers often underestimate the inherent danger, and because elevated work surfaces are quite common in construction and maintenance projects. Fall-protection strategies are a critical component of safety programs, but workers don’t always understand proper fall protection strategies and the correct use of personal protective equipment such as shock-absorbing lanyards. That creates both a false sense of security and the very real prospect of danger.
How far will you fall?
It might seem obvious that the potential distance for a fall is the key consideration in identifying proper fall protection, but it’s a concept that’s lost on many workers. You can wear the highest-quality lanyard available and tie it securely to a safe anchorage point, but if you haven’t properly computed the fall distance, you may hit the floor before that lanyard has the opportunity to do its job. Or, you may find yourself dangling in an uncomfortable and potentially dangerous position while your co-workers struggle to find a way to rescue you.
The physics involved in computing fall distance can be complex, but the math needed on a worksite is quite simple. When manufacturers test products such as retractable or shock-absorbing lanyards, they usually do so in a vertical situation. The fall distance is generally determined by measuring from the anchorage point, adding the length to which the lanyard will stretch out, plus the length of the body.
Let’s consider a situation in which a six-foot-tall worker is using a six-foot shock-absorbing lanyard that has been attached to a full-body harness. The lanyard’s specifications note that the maximum elongation of the shock absorber as the worker decelerates is three and one-half feet.
If we add the worker’s height to the length of the lanyard, and then add in the maximum elongation, we arrive at a total length of 15 1/2 feet. Most people would assume that this would be the potential fall distance, but we actually have to take another step.
What if the harness hasn’t been fitted properly, or the worker loosens the leg straps to make them more comfortable? Suppose he’s really 6’3” tall? Suppose he has overestimated the height of his work area? The best way to account for potential situations such as these is to add in a safety factor of three feet.
Doing that brings the total safe fall clearance distance in this example to 18 1/2 feet. In other words, the worker must attach his fall protection device to an anchorage at least 18 1/2 feet above the floor or the equipment that’s below the place where he’ll be working.
What should he do if the available clearance is less than that? In those cases, workers (and safety professionals) will need to consider the use of other safety equipment, such as self-retracting lifelines (SRLs).
The general guidance is to tie off to an anchorage point that’s as far above the worker’s head as is practical. Doing so will reduce the chances that the worker will strike the ground or objects underneath the work area. It will also limit the potential fall distance and the forces his body will experience in a fall, and may even keep him close enough to his work area to allow for self-rescue if he falls.
Finding a safe anchorage
The highest-quality personal protective equipment becomes worthless when a worker uses it improperly, and that holds true for personal fall-protection equipment. A worker can use the best lanyard available, but hooking it to an unsafe anchorage point will provide a false sense of security.
Just because a potential anchorage point is part of the structure or made of a presumably strong material such as steel will not ensure that it provides a safe place to attach a lanyard personal fall protection device. The standard construes that an employer may establish an anchor point of a tolerance that is more or less than 5,000 pounds as long as the entire fall protection system maintains a safety factor of two per its anticipated load, and is designed, installed and used under the supervision of a qualified person. Additionally, the standard requires employers to establish the 5,000 pound rating for anchorage if it will not be used under the supervision of a qualified person. According to OSHA, a “qualified person” is one who, by possession of a recognized degree, certificate or professional standing, or by extensive knowledge, training and experience, has successfully demonstrated the ability to solve or resolve problems relating to the subject matter, the work or the project.
Rather than allow workers to choose their own anchorage points before beginning a task, safety professionals along with the qualified person should identify appropriate anchorage points before work begins. They need to consider the highest possible tie-off locations, where staff will be working in relation to the anchorage points, and then identify and mark safe anchorage points. That way, workers won’t have to guess where they should tie off, and they’re less likely to tie off to a site that can’t safely support them. Consulting with the architect and structural engineer is an added bonus. Remember, proper planning prevents poor safety performance.
In addition to considering structures, thought should be given to fall protection when lift equipment is being used. Safety professionals need to identify appropriate options for fall protection in these situations and consult with the lift manufacturers.
Consider more than vertical distance
In discussing fall distance, we generally focus on the height involved in the task, but it’s just as important to look at the horizontal aspects. For example, if a worker falls, his body may swing back and forth in a pendulum effect. He could easily swing into other workers, nearby structures, or even equipment that is moving or dangerously hot.
A common situation is that a worker who is going to perform tasks at multiple locations on a roof or open floor area will select a retractable lanyard to allow freedom of movement. He may believe that once the lanyard has been secured, he can move anywhere in that range with complete safety. But that isn’t the case, because if he stretches the lanyard out horizontally and falls over the edge, he may fall the full distance before the safety clutches can kick in. He could hit the ground, or could find himself swinging like a pendulum. That explains the recommendation from most manufacturers that workers use no more than a 30 percent offset from the anchorage point to the body position.
Another consideration when choosing a tie-off location is hazards that may be located within the potential fall area. For example, if energized equipment, moving machinery such as exposed drive shafts, or other potentially hazardous objects are in the immediate area, the fall distance must ensure that the fall will be stopped before the worker comes in contact with the hazards. Think about impalement hazards, too. Workers may neglect to place rebar caps on bars sticking out of forms, so roofers or others working above the forms may be at risk for being impaled upon the exposed portions of the rebar.
Fall protection in warmer weather
Humans have an innate desire to feel more comfortable, and that can lead to increased hazards on a worksite. When temperatures and humidity increase, workers may begin to resent their fall-protection harnesses. It’s not unusual for them to respond to heat-related discomfort by loosening the straps, but doing so dramatically reduces the protection the equipment provides. If one set of straps is loosened, the others (usually the leg straps) will end up providing most of the support in a fall, which could cause an injury.
If hot weather (or hot work) conditions create these issues on a jobsite, a safety professional can recommend several solutions, such as harnesses made with material that wicks perspiration away from the body (similar to the apparel worn by athletes). Some harnesses allow for options padding that can improve comfort. Workers may be tempted to remove their shirts and use their harnesses on the bare skin, but this could create more pain in the event of a fall.
Also consider issuing clip-on water bottles with drinking tubes to workers who use fall protection it hot areas. They may not have easy access to water sources, putting them at greater risk for dehydration and heat illnesses.
Consider rescues
A worker stumbles or slips, and his fall protection arrests the fall before he can become injured. He’s out of the woods, right? Not necessarily. A worker suspended in a harness has to be brought down within five minutes before he can begin to lose circulation in his legs and even develop blood clots. If the pressure is relieved too quickly, the sudden rush of blood through the circulatory system can lead to other problems.
If you’re counting on local emergency responders to bring him down, they may not be able to reach your location within that time frame, so it’s critical to develop your own rescue plan for all of the elevated aspects of your project before work begins. The plan should address how you’ll recover workers who are conscious, and what type of equipment on the site – such as vertical lifts, manlifts, or ladders – are available. It should also include training for employees in the area.
Making sure all employees in the area know the proper rescue procedures is extremely important, because well-intentioned efforts to help may actually complicate the situation. A worker who reaches down to grab the lanyard and pull his co-worker to safety can easily injure himself, turning one elevated rescue into two. If the suspended worker is unconscious or has significant injuries, pulling him up may worsen his condition and make it more difficult for the rescue team to provide assistance.
Training provides the best protection
Lanyards and other devices can help protect workers from the hazards associated with falls, but it’s all too easy for workers using those devices (and the supervisors responsible for them) to become complacent about safety.
Companies that want to protect workers from falls need to place a high priority on training everyone involved. In addition to proper identification of anchorage points and use of equipment, that training should ensure that everyone knows what to do when a mishap occurs. That knowledge makes the difference between having only a perception of safety and achieving effective protection.