Hello, a number of our workers are familiar with Fire Fighting Bunker gear being retested before going back in service after a fire and have asked how we know they have washed off combustible materials adequately from their FR-Arc Rated work clothing to safely put back in service.
Does anyone have any established approach on this subject? Kind regards, Jason Hoffman

There's no retesting I've ever seen done. The actual test for the fabrics (ASTM 1959 is not a clothing test, it's a fabric test) is destructive. You expose samples of cloth covering copper calorimeters at different distances to an arc source looking for the threshold value where either 50% of the samples break open or 50% of the samples fail to keep the incident energy measured by the calorimeters below the Stoll curve. The Stoll curve is based on the onset (50% point) of a second degree burn on human skin. It is about 1.2 cal/cm2 at 1 second, and grows to about 2 cal/cm2 at 2 seconds.

Needless to say, you can't duplicate that kind of test in the field, nor is it in any way a nondestructive test.

A Canadian mining company had several work uniforms (coveralls) tested under various typical working conditions for them (soaked in salt water to simulate sweat, used uniforms after 2 years in service, soaked in oil, smeared with grease). The only case that really "failed" as such is the grease test. In this case they smeared a huge glob of grease on a uniform. What happened in the video is that the grease lit on fire and burned for several seconds after the arc flash stopped, and eventually went out. The uniform itself as I understand it from someone that sponsored the test didn't look all that damaged. The cloth itself doesn't support combustion so essentially from what he described and it looked like on the video, the grease lit on fire and burned, then went out, leaving the uniform with minor damage. This test failed the ASTM 1959 test because of the grease fire, not because the FR PPE actually "failed" by itself. It's been almost 10 years and I'm sure if I've misspoke here Hugh would respond but to me this was a real eye opener as to conditions other than an office environment.

Suggest carefully reading and following the manufacturer's laundering instructions, followed by examining the garment for fraying.

Hello,
Just repeating Paul and Steven's reply above. Pending on the type of fabric your workers are wearing, you may want to check out a series of arc flash videos @ www.westexinc.com follow your way to the videos section. They have a number of videos produced with a maniken wearing arc rated flame resistand clothing after it had been laundered 100 times in an industrial laundering facility. As they mention and as is also mentioned in the previous comments, to follow the manufacturers laundering instructions. Finally, more than a few years back, Hugh Hoagland together with the Mining Safety Association and the Electrical Safety Authority up here in Ontario produced a presentation called "The effects of Contaminants on arc rated clothing and PPE". It is excellent. I believe you can view the presentation/ videos from the ESA (Electrical Safety Authority) web site or just google "effects of contaminant on PPE and clothing. Hope that this is of some help

More technically there are really 3 issues to consider when it comes to FR PPE for arc flash purposes. The first one is preventing the material from sustaining a flame. All of the inherently FR fabrics (aramids such as Nomex, Kevlar, or Spectra) or the ammonia-treated cottons such as Westex Indura or Glengard have this property. It doesn't go away. Some of the old "welding greens" use a process that basically coats the cotton that does wash out over time so just be carefl to look for ones that are "inherently" FR.

The second issue is "wearing out". The actual thermal property of the fabric is basically how insulative it is. Ordinary cotton shirts are good for around 10 cal/cm2 up until the point that they ignite...which is why the treatment process or inherently FR fabrics are necessary. The only way to raise the ATPV of course is to make it thicker. You can get up to about 12 cal/cm2 with one layer. After that it has to be multi-layer, whether it is a single PPE garment such as a "40 cal suit" or a tested combination. At this point in reality there is nothing special about the PPE other than how well it thermally insulates. Not surprisingly a lot of winter workwear made out of FR fabrics has very high inherent ATPV ratings. But more to the point if it is ripped or frayed to the point that it won't "keep the cold out", then it won't work effectively as arc flash PPE. But up until that point, it still functions just fine. That's what the mining video shows very clearly.

Third issue is contamination. This means that soaked in fuel or oil, smeared with kerosene, or wearing non-FR clothing which can melt over or under it such as wearing a hi vis vest over the top of it or wearing a nylon lined winter jacket over or under FR PPE in winter is a bad idea because it can melt and/or ignite and cause an injury under or over the FR PPE. Cotton, wool, silk, and rayon are OK because instead of melting, they just char if worn under the FR PPE but over the top is a nonstarter. This also leads to another subtle issue with respect specifically to home laundry. Fabric softeners sit on top of the fibers and will light up so liquid fabric softeners are not allowed. I've never heard or seen anything yet discussing "dryer sheets" but my assumption is that it's probably a nonstarter, too. I've also heard that bleaches including the non-chlorine types are all bad but have no specific information on this. I don't know anything about solvent (dry) cleaning either. Most of the fabric manufacturers though have some pretty good information on laundering.

I personally wear FR PPE as standard workwear every day now. I'm a field service engineer. And I only usually get to the main office once a week on average so using the laundry service (which is free for me) on a regular basis is hard to do so I end up washing a lot of my work uniforms at home. I wash in warm water using HE detergent (I have a high efficiency washer), rinse in cold, and tumble dry on medium without bleach. I wash all my work stuff separate from my other clothes and I check it for stains and do it again if I spot anything before it goes in the dryer. If that doesn't get it out, I'll take it to work and let the laundry service deal with it. If it's ripped/torn, I tag it and turn it in for repair/replacement.

Personally, I'm probably in a high risk category right up there with linemen. I'm a field service engineer. I'm the guy that gets called by all the plants that are too small to have electricians on staff or where the electricians they have can't figure it out or are afraid to work on the equipment. So often I'm working on gear that probably doesn't come close to the definition of "properly maintained". I have FR PPE and I use it, every day. I haven't had an opportunity to "test" it in my current job but I figure it's just a matter of time.