Sent Sunday, May 12, 2001
Is ASTM 462 (on Bathing Surfaces) a Valid Standard?
I regularly get calls and questions about ASTM F462, Standard Consumer Safety Specifications for Slip-Resistant Bathing Facilities. My users typically want to know how to test a bathtub or shower base with the English XL according to this standard. The answer is that you can't. But more significantly, why would you want to?
Background on F462
I have often heard Bob Brungraber say that this standard was developed for the CPSC to give them a test method that would pass all treated tubs and shower bases and fail all smooth ones. There was no study performed to determine what traction level is required for safety on bathing surfaces, and the passing score according to this test bears no correspondence to a threshold of safety, though it probably would be a fairly effective test of safety for surfaces that are new or pristine. It is absolutely ineffective for predicting the effectiveness of such surfaces in actual use, however.
The Test Protocol
The F462 standard calls for testing surfaces with a Brungraber Mk I (PAST) fitted with a Silastic slider pad, and it is performed with a very rich soapy water slurry on the interface. A passing score is .04! According to F462 only the PAST can be used. You can't test to this standard with any other instrument. Probably testing could be done in bathtubs using various other slipmeters with Silastic pads and the soapy film specified to devise a spreadsheet assigning a threshold of safety to each instrument. But this would serve no useful purpose for several practical reasons.
Why the Standard Does Not Work
The primary problem is that it is the soap scum that builds up on the tub surface (due to soap and shampoo interaction with water hardness and other contaminants) so as to apply a smooth coating over the slip-resistant surface, making it dangerous. The bather is not standing on the textured surface that was tested when the tub was new, she is standing on the soap scum film, which levels the texture significantly, reducing its slip resistance to a dangerous level. In actual normal usage, even treated tubs fail to perform adequately after a few weeks.
Also, the soapy water mixture is a bit problematic. The originally recommended liquid soap product became unavailable, and there was even some question about its consistency. But even if a consistent product were easily available, the resulting slippery mixture does not represent anything that actually goes on between a bather's foot and the tub surface while showering. If you experiment in your own shower, you'll find that the only way to get soap on the interface between your foot and the tub is to pick your foot up and soap it before putting it down. Shuffling it a little washes the soap away adequately.
Actually, a minute concentration of soap in water does not increase the slipperiness of a wet surface anyway. In tests I performed with the English XL (VIT) for a manufacturer of tub and shower mats we found that adding a small quantity of liquid soap to the test water actually increased the traction performance. I theorize that the wetting agent in the soap made for a thinner film which was more tenuous than pure water would have been. It is therefore my position that any bathtub/shower traction test should be performed with H2O as the lubricant. That is more representative of real-world conditions and is less problematic than soapy mixtures on several parameters.
So far I have seen no convincing reason why tubs and showers tested with the English XL (VIT) using the normal Neolite pad and water for wetting should not have the same .50 threshold of safety as normal walking surfaces. A special standard for bathtubs is not needed. But if you're interested in this problem, why not petition ASTM F15 to reconsider the F462 standard? It should probably be withdrawn.
But All of That Is Irrelevant
I have never metered a tub in a fall case, although I have done a number of them for both plaintiff and defense. The reason is that I never get called to consult until months or years later, and there is no way in the world that I could prove that what I am testing is the same condition that prevailed on the day of accident. Further, many defendants know how to have the tub treated before authorizing the testing by a plaintiff's consultant so that it passes. So unless you are standing out in the hall with your slipmeter in your hand at the moment of a tub or shower slip/fall, you'll be crossing a minefield if you start testing long after the fall occurrence.
I find that I have always been able to work from the plaintiff's fall scenario and the physical evidence. If the plaintiff's story is consistent with the physical evidence and human factors parameters, the ladies and gentlemen of the jury will likely buy the plaintiff's account after you explain its validity. If on the other hand the plaintiff's story doesn't match up with the physical evidence and the ergonomic body of knowledge, it is not difficult to persuade reasonable people that the claim is flawed, if not fraudulent. Actually, I have never testified in court or even in deposition in a tub fall case. They have all settled on the basis of my report, except for a couple of plaintiff cases I declined to accept because I didn't believe the plaintiff's fall description.
The answer to the tub fall dilemma is to not accept funny plaintiff cases and not to try to impress the jury with junkscience, even when using the world's best slipmeter. It all boils down to whether you're really an expert. Buying a slipmeter won't make you one, but even if you really are one, it is often better not to test.
What Is the Remedy for Slippery Tubs?
An insert rubber mat placed in the bottom of the tub will enhance traction, and installation of adequate grab bars on the walls of the shower enclosure will offer a means of possibly arresting an incipient slip/fall. Tub mats are not a sanitation problem. They can be laundered as easily as the towels and bathmat.
William English, Inc.
Phone 239/728-3254, FAX 239/728-2304.
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Copyright 2007 William English. This page may be forwarded freely if not altered in any way, but reproduction without the written permission of William English is prohibited.
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