Fall Arrest Systems:can workers tie off at foot level?6 min read
Your Company just scored a complex new construction project. Your task is to plan out the fall protection – but this project is a tricky one. There aren’t many options for overhead anchorage points. So you wonder, can I have the workers tie off at foot level instead?
For workers at height, fall arrest systems are, quite literally, lifesaving systems. But like most safety devices, they’re only effective if used properly. Falls represent 39.2% of worker deaths in the construction industry. It’s clear that fall safety should be the top priority for employers and employees alike.
So, can workers tie off at foot level and still remain safe? Generally speaking, this practice should be avoided. However, with the proper equipment and training, it is allowable. If it is necessary for your project, there are a variety of factors to consider before going this route.
Clearance Is King
The most important factor to consider when tying off anywhere is clearance. OSHA requirements provide insight on the rigging of personal fall arrest systems. They state that a worker cannot free fall more than six feet or come into contact with any lower level.
Workers tied off at foot level experience a greater fall distance in the event of a fall. It’s not uncommon for them to exceed a six-foot free fall. This is only permissible if the employer cannot provide a more suitable anchorage or other form of fall protection. Of course, this means that you need more clearance to arrest the fall, and not all worksites have that kind of space.
Puzzlingly, neither the OSHA regulations under Title 29 CFR nor the ANSI Z359 standards present a clear and simple method for calculating clearance. It requires a little bit of critical thinking. ANSI Z359.6 (Specification and Design Requirements for Active Fall Protection Systems) does present some useful information, although you may find it dry and overly technical.
At its most basic level, the following variables need to be taken into account:
- Available Clearance (AC): AC is the distance from the position of the anchor to the nearest obstruction
- Required Clearance (RC): RC comprise the total fall clearance that your equipment will require based on your rigging; it must be less than the total distance
- Lanyard/Device Length (L): This is the total length of the lanyard (often six feet)
- Deceleration Distance (D): This distance involves the elongation of the deceleration device (e.g. shock pack on lanyard) when deployed (calculations should use a distance of 3.5 feet, or the specification of the manufacturer)
- D-Ring Height (H): This is the distance from the worker’s feet to the dorsal D-ring on the harness
- Stretch Out (SO): This is the additional distance attributable to the shifting of the D-ring and stretch exhibited by the harness at the conclusion of the arrest
- Extra Clearance (C): Extra clearance is the distance from the obstruction after a fall; it must be at least 2.5 feet
Given this information, the equation to calculate fall clearance looks like this:
RC = L + D + H + SO + C
(Where RC must be less than AC.)
Hazards to Consider
Working at heights poses a degree of danger. Tying off at the level of the walking-working surfaces comes with its own set of risks. Before moving forward with this practice, it’s critical to conduct a thorough risk assessment. You can then determine what hazards workers face and how to address them.
Workers must be careful not to tie off in such a way that will cause them to swing into an obstruction if they fall. These swing-fall hazards can be as dangerous as falling to the ground.
Delayed SRL Lockup
Self-retracting lanyards (SRLs) work like seatbelts. They’re designed to lock up when the cable leaves the housing at a certain speed. But SRLs anchored at foot level don’t reach this threshold until after the worker’s D-ring is past the leading edge and below the level of the anchor. By the time the device knows to lock up and arrest the fall, the worker has already free fallen about five to seven feet.
(Check out Fall Protection Fundamentals: Self-Retracting Lanyards to learn more.)
Impact on the Body
Free falling can be tough on the body. Tying off at foot level results in a greater fall distance. As a result, the body absorbs greater force from the fall. Workers anchoring at foot level should use a fall arrest system with energy-absorbing devices that are designed to absorb the impact forces that can result from this added free fall distance. Products rated for leading edges typically offer this added protection.
(Find out how much clearance you need to use a leading edge SRL.)
Leading Edge Hazards
If you are tying off at foot level, you may be exposing your connecting device to leading edge contact. The edge may be sharp, abrasive, or serrated and could cause significant damage to your device.
You may have noticed that there are a lot of “Leading Edge” products available nowadays – it is important to note that most of the testing that is done to validate these products in the ANSI Z359 standard simulates best-case scenarios in steel erection. Elements of risk found in various concrete construction and deck work are not simulated in these tests. As a result, many of these products may not offer the protection that you may be expecting.
The Right Equipment for the Application
While a standard energy-absorbing lanyard will work for most applications, tying off at foot level is not one of them. The special equipment needed for this practice is often overlooked. This can result in unnecessary safety risks.
If you are using an energy-absorbing lanyard, ensure that it is rated for a 12 foot free fall. If it is not, you will see an arresting force that exceeds the 18,000 lb limit and may cause injury to the falling worker – or worse, it may fail to arrest the fall entirely.
Self-retracting lanyards can also be a good choice for arresting falls. But generally speaking, most are not capable of dealing with the forces associated with free fall distances seen in foot-level tie-offs. If you choose to use some type of self-retracting lanyard, ensure that it is rated for the type of free fall that it will be subjected to in a foot-level tie-off (most are not). If there is a leading edge hazard, make sure that the product you are using is leading edge rated, and consult with your manufacturer of choice with regard to the specific characteristics of your leading edge.
It’s also important to note that the required clearance distances for these products can be anywhere between 13 and 18 feet. Typical clearances when tying off overhead range from only 10 to 15 feet. There is very little margin for error and this gear may not be suitable for every worksite.
Overhead Anchors vs. Tying Off: It’s a Matter of Safety
Anchoring at foot level should be a last resort. Only use it when there is no suitable alternative. As a rule, the best outcomes always come from workers tying off to overhead anchors.
Anchorage points that are higher than a worker’s dorsal D-ring are ideal. This positioning means the device will engage to arrest the fall quickly. It prevents the worker from free falling too far and minimizes the impact on their body.
Horizontal lifelines function as an extension of the anchorage system. They allow a worker to move back and forth across a work area. Employers must ensure that horizontal lifelines, if used, are installed correctly. Proper installation minimizes sag and limits the distance a worker can fall.
Of course, the equipment needed to keep workers safe is only effective if it’s used right. For this reason, it is critical that employers invest in thorough training for workers who are using fall arrest systems. It is crucial for crews to understand their safety risks and the procedures to follow to stay safe. This is especially true if tying off at foot level is the only available option.
Tying off at foot level isn’t prohibited under OSHA regulations. But best practices dictate avoiding this option if at all possible. Alternatives exist that keep workers even safer. And that, at the end of the day, is what really matters.