Random Numbers

By David H. Glabe, P.E. / November 1, 2009

As a prime example, take the standards that relate to the height of toprails in a guardrail system.  Here are the numbers: 36; 38; 39; 42; 45; 48.  How about the height above the level below when fall protection is required?  Here are the numbers:  5 feet; 6 feet; 7 and a half feet; 10 feet; 15 feet; 30 feet.  And just for fun, midrails on a guardrail system are to be either “halfway” or “approximately halfway” depending on which standards apply.  (Can you imagine the “halfway” concept: off by 1/64th of an inch and you just violated the standards!)

Dimensions and measurements are not limited to fall protection but these numbers typify the contradiction in the industry.  It is particularly nasty for those who “just want to build scaffolds” as one frustrated scaffold erector told me.  So, how random is it?  Let’s take a look at the height at which fall protection is required.  The OSHA Maritime standards require fall protection at 5 feet while the OSHA construction standards require fall protection at 6 feet except for scaffolds where the height is 10 feet.  The Army Corps of Engineers, in their recently updated standards, determined that fall protection should be required at 6 feet for all situations including scaffolding.  Apparently things are more dangerous in military construction after all.  Or maybe workers on construction scaffolds know how to fall safely.  Actually there may be a legitimate reason why guardrails are not required for scaffolds until 10 feet above the level below.  It’s based on the increased hazard of attempting to work from scaffolds in the typical commercial ceiling height environment while contending with a guardrail system.  Why the Army Corps chose not to agree with that is unknown to me.  But then, as far as I know, the Army Corps didn’t ask anybody in the Scaffold Industry Association for any comments regarding the revamped Army Corps standards.

What’s interesting about all of this is the apparent lack of solid scientific data to support the numbers.  It is often argued that death can occur from any height—and it’s true.  For example, I am aware of a worker who fell backwards off a scaffold platform approximately 4 feet above the ground.  He unfortunately hit his head on a concrete block and died instantly.  But, on the other hand, you hear about workers who fall from 20 or 30 feet without any lasting injuries, much less death.

So where do the numbers come from?  Based on my research, it appears that much of it extends from earlier standards and codes; unfortunately, the real, original basis for these disparate numbers is lost to history.  In other words, we seem to perpetuate the randomness of the numbers.  I don’t particularly have a problem with that.  For example, 42 inches seems to be a good number for a guardrail height.  (Far be it for me to argue what so many people agree is the right height.  Besides, I don’t have any research to argue that 42 inches isn’t a good height. However, I wonder what the National Basketball Association might have to say about it.)

The real mystery here is why there is so much variability in the required heights and distances.  Why does California insist on a 7’-6” height while the rest of the country is at 10 feet?  Why do the Maritime standards insist on a threshold of 5 feet and the Army Corps of Engineers insist on 6 feet?  The erector I mentioned earlier erects scaffolds in California, Arizona, Nevada, Washington, and Hawaii.  One week he may be erecting scaffolding in a shipyard in Washington (Maritime applies) or maybe at an office building in Seattle where Washington OSHA (WISHA) standards apply.  The next week he may be in the middle of California working on a scaffold at a water treatment plant where California OSHA (Cal/OSHA) standards apply.  But if he is on a Native American reservation in the middle of California, the federal standards apply.  Hopefully he doesn’t go next door to the US Army VA hospital because the Army Corps standards apply!  Unfortunately, the following week our confused erector is in Nevada working on a casino in Las Vegas and since Nevada is a “state plan” state, he must know the nuances of Nevada’s standards.  From there our erector goes to Arizona which is also a state plan state with its own peculiarities.  Hopefully our erector doesn’t have to travel to Hawaii anytime soon; it’s a state plan state too with the potential for variations in the applicable standards compared to other jurisdictions.

Surprisingly, it appears that most, if not all, the standards agree on one thing: the strength of the toprail shall be no less than 200 pounds.  If we can agree on that, why can’t we agree on the rest?  Oh, by the way, those numbers I listed at the beginning of this article are all real and correct.  Do you know which standards they came from?

Tags: Fall Protection Scaffolding Army Corps of Engineers OSHA Standards & Regulations Resources WISHA

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David H. Glabe, P.E.

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