UKH

I thought they lasted a lifetime then I read somewhere of one failing during a fall which got me wondering. 

Manufacturers will say 5 years (or sooner if it's obviously worn).  Many will keep theirs beyond 5 years (but, hopefully, not as long as Todd Skinner's harness, that failed when 21 years old), and obviously it depends on how much use it has had.  I'd go mostly on how it looks -- does the stitching look sound, or does it look a bit frayed?

Our working a height gear is five years.

5 years for me because that's the manufacturers rule of thumb, I repurposed my harness waistbelt into a belt for my trousers.

Personally I'd go beyond 5 years for personal use, but check the wear points where you thread the rope through and stitching regularly. 

If you were to perish in a harness-failure-related accident, I guess it could then be said to have lasted your lifetime

I dug out my sturdy old harness the other day and used it at the local indoor wall, it's 19 years old and has been used scores of times on mountain ice to summer multi pitch and innumerable cragging although it was idle for about 5 years. 

Its a Troll one don't know if they are still in business but it looks OK.

So does no one else use an old harness then? 

My indoor harness is probably about 15 years old, outdoor one about 10 and neither have failed yet...

Most of the gear I use probably belongs in a museum, but I am a bit cautious about harnesses. This dates from one trip to Swanage, when the prospect of a long abseil to a hanging stance made me undo all the buckles on my trusty Littlejohn harness. I was shocked to find that the bits of the buckle concealed by the webbing had corroded to a crumbly white mess, resulting in a rapid distress purchase of a new one.  I was doing a lot of sea-cliff climbing at the time, and the whole business made me much more paranoid about the bad effects of seawater.  I’d recommend a very careful inspection...

Can anyone shed light on the hidden potential dangers of older harnesses - material/stitching deterioration/life. Wear is often visible but weakening of the material is not.

I doubt we'll hear from anyone who's harness has failed. 

<pedant>

The harness is usually going to fail shortly before you expire

</pedant>

To me it's when they start looking tatty. I make a point of un doing the buckles every few months to check the wear. Also I would probably replace between 5 and 6 years old if one got that old because UV light degrades a lots of materials so why chance it for something that can save your life?

Another point to think on, how much respect are you showing your climbing partner by belaying them from a 19 year old harness? It's not taking as much force in a fall as the climbers but it is taking the strain. 

Once it starts to get fluffy, typically round the belay loops, then the structure is weakening. 

Of course how serious that is is hard to determine. Time may be a factor but usage is more important.

For me the time to replace things, non metallic at least, is when I start to think about how long I have had it

Depends which manufacturer. Petzl, for example, give a 10 year lifetime on their harnesses (sport and work). They also have inspection procedures available to download from the website, which may be of interest to the OP.

Best advice is to read the instructions for use (technical notice) that come with any PPE that is sold. (or contact the manufacturer if you didn’t keep them..!).

Unless you cave in it as well (I wouldnt) then the inside of where the rope is threaded wears the most, as the rope constantly shuffles around, not much but if you climb lots in the same harness you can produce visible wear within 5 years. 

The waist belts are usually so over engineered even a belt 20 years old will fail at a load high enough to likely of killed the wearer. 

Not saying you are wrong at all but "usually" is not a word i look for when assessing safety critical equipment

Of course I would never presume, always check. But there are places more prone to wear than others and with critical equipment you should bin it at a time the risk of it failing increases rather than chance it. 

I have an old troll mk8 which is somewhat older than 19 years that I will wear occasionally when top roping with guests. 

I'd happily donate it to someone if they had the means to test it to destruction. My guess is that it's significantly stronger than needed, although I wouldn't use it for leading or lead belaying just due to the possibility of unseen fatigue. The waist belt is a 2 inch webbing doubled back through a buckle. Compared  to a new harness it like it would hold a tank.

-edit- might be 29ish years old. Crikey. But one careful owner

2nd edit. It has velcro on the waist loop which brings an interesting possible failure mode if you velcro it shut but fail to do the webbing up, or fail to double the webbing back, hence I won't lend it to others. And it creates most unnerving ripping sound the first time you load it as the velcro gives and the webbing takes the strain..

in the case of a lightly used harness that hasn't seen much UV I would back up Summo and not hesitate to use it myself.  Mine is over 10 years old and I'm entirely happy that it would not be the thing that killed me in a fall

Mines 12 years old and up for replacement this year. I have done ppe inspection on a professional basis and I currently have no concerns about its integrity, however, like my wetsuit it seems to have 'shrunk' slightly.

I have also done drop testing on work and rescue harnesses and I've seen a single fall put a harness out of action. Like everything, a bit of common sense is required to decide when to retire climbing gear. 

Indeed

Other than Todd Skinner, are there any other documented cases of harnesses failing (not being antagonistic, genuine question)?

I thought my harness was fine until by complete chance my mate that works in rope access happened to pick it up and gave it a once over spotted various faults with the harness which was about 7 years old one of which was very serious. It was immediately retired and I'm now considerably pickier when it comes to gear that quite literally my life may depend on. Since then I have retired another harness after about 2 years as it was showing similar signs of wear as it simply isn't worth the risk. In regards to other high profile harness failures I believe Dan Osman may be another unfortunate case?

Googling says that that was a rope failure caused by a rope crossing over itself and melting through. 

In Todd Skinner's case the cause of failure was lark's footing a daisy chain or similar to his belay loop and not checking it - the daisy gradually sawed through the belay loop.

About 30 seconds less than that. Give or take...

I've still got my Whillans Sit Harness, bought in 1979. When got back into climbing a few years ago I wondered about using it. I'm certified for PPE inspection and it would pass other than on date, and while out if use it has been in a light-proof crate. Be interesting to test it though.

But I bought a DMM Super Couloir instead...

Jeezus, how did he not notice it had started sawing though the belay loop? Was it one loop or two? I have a 10 year old harness that this thread has got me worried about. Used it about 10 times I think (mostly a boulderer). Doesn’t look used at all. Anyone reckon it’s still unsafe? I feel fine using it tbh.rope i retired as it was like 12 years old. Harness i’m hoping the dyneema like straps don’t deteriorate with time like ropes do! 

I sometimes use a non padded basic webbing DMM one that is probably about 18 years old. It spent the first eight years of its life unused, boxed, away from UV. I use it rarely, used to use it for my occasional forays into winter/Alpine. 

I have no concerns about its physical integrity but as I have a nice new padded harness I wouldn’t use the old unpadded one for anything other than weight saving and versatility (you can completely unbuckle the leg loops and waist loop, handy in a few winter scenarios etc) 

My brand new Wild Country harness failed second time out at Lundy. They'd forgot to stitch a gear loop.  It worried me greatly.

You ought to see the reps face when I told him an entire series of friends fell into the sea.😁

After reading all of the above I'm binning my old arness and getting a new before any further climbing. 

Crikey! That's a bit of a let down. Hope you were suitably reimbursed.

All of the manufacturers have different recommendations, very few of them are set at 5 years, with the majority around the 10 year maximum life span point. 

It is worth having a look at this document - https://www.facebook.com/notes/rock-and-water-adventures/summary-of-manufac...

I put it together a couple of years ago, as I was fed up of people coming up with random rules of thumb, that they had heard from their mate in the pub (or perhaps an internet forum) instead of reading the information that comes with the item of climbing equipment, when they purchase it.

Contrary to popular belief the lifespan of all climbing software (ropes, harness, slings) is 10 years from the manufacturer.

There are outside factors which will reduce this, sometimes significantly. Ebrasion, general wear, large impact, chemical contamination, cuts, and damaged stitching to name a few.

Some you'll know will have happened and always worth a quick once over of a harness before you put it on as most climbers just bung in their rucksack and stick it on next time.

Does that apply to the fabric bit on friends to even if they haven't been used much? 

Though if one manufacturer says 5 years and another says 10 years, it is likely *not* because the products are different in this regard, but more likely that the manufacturers are adopting different levels of caution. 

That's interesting. What's your source? Given different materials involved it sounds like a policy rather than empirical data.

Bearing in mind that HSWA  & WHR ( & SI 735, 1019 etc) don't apply to non-professional activities

I am 70 and I have no intention of binning my harness. The though of going back to tying the rope around my waist, or soloing at my age scare the crap out of me!

It's classed as a soft item the sling, so unfortunately yes. 

However it's manufacturers recommendations and I may have one or 2 cams which exceed their recommendations. Ropes and harnesses usually don't last that long due to use and unlike gear you place on a climb wouldn't have a secondary backup if it failed in the main.

If you want to go by the book look at the manufacturers details, many did say 5 year but that took into count time spent in warehouses and shop shelves. These days most manufacturers give 10 years from manufacture, when you buy the item it will have the manufacture date on it as part of the BS-EN certification for the product. Things like ropes will often be dated at the ends.

If in doubt contact the manufacturer who are always happy to help.

The source I use for ropes, slings and harnesses are what the manufacturer supplies with their equipment. HSWA  & WHR ( & SI 735, 1019 etc) don't apply to non-professional activities, but if you have a client and the shit hits the fan you will end up in court and have to justify why you ignored the manufacturers recommendations as you should have a recording system for the equipment.

After that I also go with the IRATA guidelines and use which ever is the shortest lifespan, but both are usually 10 years for soft items unless wear and tear, damage or potential contamination is found.

If just for personal use, up to you really. Pease of mind would be my main reason for replacing kit as per the manufacturers recommendations if I had't treated it already.

Some interesting results ( quite a few reports like this around.

https://eu.blackdiamondequipment.com/en_GB/experience-story?cid=qc-lab-old-...

Fair enough, and many thanks.

There is and I've read the article before.

Everything has a finite lifespan, from a work point of view I stay within the manufacturers perimeters as I wouldn't have a leg to stand on if I did not.

Recreationally I use common sense which is difficult to put across online to cover every bit of kit without knowing the history, users experience of kit and often the exact age. 

Hence go with the manufactures recommendations and then your own experience. I've seen new kit fail when it shouldn't and probably have some cams that are 20 years old that I'm still happy to use recreationally, with mates who have similar aged gear.

Definitely a sensible policy, and especially for professionals. The biggest danger is perhaps a false sense of security if the equipment isn't solely under your own usage and control. Eg petrol contamination in the boot of a car. Also knowing the wear, tear and number of falls you've had ( Do guides keep a kit log?)

This also happened to me some years ago on the Old Man of Stour. Fortuitously my rack landed on a ledge and I downclimbed to it without epic.

I got chastised for my daughters 7 year old harness at a wall, then he turned his attention to my 17 year old one. Apparently on this chaps course 3 years was the max 

Climbing wall police have an education of their own, possibly Hogwarts

The occasion that prompted me to start inspecting my harness more thoroughly, was being hoisted in to a helicopter whilst being retrieved during a rescue in the Alps.

The belay loop is the only sole point of attachment to the helicopter winch wire, certainly focusses the mind whilst x amount of meters off the deck.

Additionally using a cows tail or sling larks footed around the belay loop, attachment points & carrying out lots of abseiling increases the wear rate quite dramatically as I found out on a old harness.

 Not true. Have a look at the link that I posted above. For harness it ranges from 5 years use to 10 years from first use, or 15 years from manufacturer.

and when you abseil... or use self belays at wall

He knew it was worn. He discussed it with his climbing partner three days before the accident. At the time of the accident he was abseiling on a low stretch rope using a Grigri attached to the belay loop with a screwgate. Any jerking on low stretch exerts a very high load. 

While I rarely get more than 10 years out of a winter harness my rock harness, despite thorough and regular inspection, is entering its 4th decade.

If you have a paying client it would be a professional activity so I would think that the HSWA & WAH regs would apply? 

I just checked the first harness manufacturer on your list - Blue Ice which you said had 5 years use.

The manufacturer now states that all Blue Ice textiles must be disposed of after 10 years now. Things do change so the only way to know for sure the life expectancy of a bit of kit is to read the attached label at the time of purchase or contact the manufacturers.

Don't bin it! Simply colour in all the UV faded bits with permanant marker and you'll get loads more for it on ebay.

Insert <not serious> icon of choice here______

You do know that the numbers are completely abitrary? We are required to give the expected lifetime of the product but the standards give no indication of what the "end of life" parameters are.

Same here, but I thought the manufacturer deserved a lesson. 😁. Plus the rep was an old climbing partner who initially regarded my route claims with suspicion.  Ended up having to video ascents. It was a pleasure to hit him with my first lie

  I recently retired a harness as it looked pretty well used and a bit tired. I cant see a better test than visual inspection 

Useful information on degradation of nylon from various contaminants here. Petrol and diesel are both chemically very similar to a harness so not much effect. Acids are quite another thing.

https://www.calpaclab.com/nylon-chemical-compatibility-chart/

Worth noting, in the carboot scenario, that Antifreeze has severe effect.

And which bits of your harness are nylon? Many (like my BD ones) use polyester because it´s better.

That's fascinating. I thought I'd read somewhere that petrol and diesel were particularly bad for nylon rope integrity precisely because of the shared hydrocarbon nature (and that gelled with thinking of solvents generally working best in a like with like pairing). Still, the chart does explicitly state what is meant by compatibility and rules out loss of strength.  It's good news though. Any more corroboration available?

Isn't polyester more oleophilic than nylon ( why polyester trousers get mankier than nylon).  "Better" needs to spelled out in respect to which properties are needed for the application.

This is the key point I think Jim.  It's sensible to have a strategy for personal kit, and it's legally mandatory to have a policy for professional and commercial use. But the strategy/policy needs to cope with a fair amount of ignorance and uncertainty. We don't have enough knowledge or control to remove risk altogether but we can operate in practical ways to reduce the highest foreseeable hazards. Single point failure systems can be avoided wherever possible, and even a harness can be designed to minimise the effects of a single material failure ( I'm not saying they all are, but one can be).

I was pointed at this a while ago on an equipment inspectors course, similar for Polyester here

https://www.engineeringtoolbox.com/chemical-resistance-polyester-d_784.html

Cheaper, stronger, better wear resistance, higher UV resistance and low stretch so you don't fall out. And polyester is recycleable. There's no good reason to use nylon I can think of.

Every time I used my old Troll harness at the wall the staff very kindly offered me one of their hire ones free of charge. In the end I was so embarrassed that I bought a new harness. At least I didn't turn up in my Whillans!

From the shop at the wall I hope?  They deserved your custom after making such a polite and patient sales pitch.

I thought nylon was stronger? Polyester less dynamic. But the comparison is often made for tents and clothing with their pros and cons. I suppose the needs of harnesses and climbing slings and lifting gear all differ.

Apropos of nothing really, last year I replaced the 7 slings I carry with those Edelrid ones that are Dyneema wrapped in nylon.

Well nylon is stronger as a material but polyester comes with finer threads so can be woven tighter. Polyester doesn't absorb water so wet it has the advantage.

Cheers Why so much nylon around do you think? I can see plusses for slings, but what's your take on it?

I bet if you load tested to failure, your troll harness waist belt it would equal many newer so called lightweight harnesses. 

There was a BMC tech document back in the 80s or 90s about ropes. They had obviously had a lot of fun mistreating nylon climbing ropes in dozens of ways. The conclusion was that sharp edges during falls and urine were the two things that would kill your rope. 

So what I take from that for harnesses is that contamination with urine (or AdBlue) will reduce the strength of nylon components. (I have no information on this for polyester.)

- This should focus one's mind on the proximity of one's harness and tie-in when taking a leak!

- Do you hang your gear up somewhere where there are bird or rodent 'visitors'?

- Do you chuck your gear in the back of the van next to the adblue bottle?

I find it hard to believe the numbers are completely arbitrary, that would mean they were based on random choice or personal whim, rather than any reason or system. The amount of research and scientific data on how materials degrade much have played a part in the decision of in the main 10 years for webbing items. Up to about 15 years ago most webbing only had a 5 year manufacturers lifespan; there must have been discussions, testing, review of data and a general consensus that 10 years (without any other factors) was a reasonable time? I don't see 10 years lifespan just being picked out of a hat.

I very much doubt that a manufacturer would accept any responsibility for the failure of a webbing item that was 11 years old even if it had never been used before. I also very much doubt I'd get any support from a manufacturer if I ended up in a court as a result of a webbing item failing in a work situation if it was more than 10 years old, again even if it had never been used before.

A judged balance between persuading climbers to buy new gear often and not frightening them off to another manufacturer!

With no provision in the standards for when a product is no longer safe any stated lifespan is merely a whim, no more, no less. Show me anywhere that a manufacturer says at what strength a harness is too weak for further use.

As an item of personal protective equipment even in recreational use there has to be some form of indication of when to retire. Easy enough with hardware as as long as it is not mechanically damaged, corroded or been exposed to large forces it is still be safe to use as the material it is made from does not degrade and strength lost.

A harness or other webbing the only way to test its current strength would be through destructive testing at which point you'll not be using the harness again even if it passed the test.

I'm sure the webbing manufacturers will have tested the materials of differing ages used in a harness to come up with the expected lifespan, taking into account the expected degradation of the materials due to ageing.

An interesting topic, and something I'll research further myself.

You've just got to find the magic number, where the harness goes from "safe" to "unsafe".

A bit like a left over turkey and stuffing butty, was happy enough eating one today but glad there's none now left for tomorrow

Not sure I fully agree with the 'whim' but yes there is a degree of arbitrariness ("is that a word?... it is now...") around lifetimes for textile/plastic PPE. The manufacturers I have involvement with all have a process (many processes) of risk analysis in place which will cover amongst other things giving a recommended max lifetime which leaves them with plenty of margin of safety in hand to cover their behinds in a worst case scenario. They do also 'weather' & 'age' products and re-test against normative or internal tests as well so numbers are not completely plucked out of thin air.

re the polyamide/polyester debate one point of view may be that if polyamide is more elastic this may be a desirable quality in terms of helping reduce peak forces in systems. In the same way that semi-static rope is and has for some time been the norm in rope access work as it is a good compromise between the efficiency for jugging or working of the low-stretch, but still with a degree of energy absorption. Static/hyper-static ropes would be way more efficient particularly for upward movement, but need way more careful handling from the user to avoid high peak loads on anchors & user... So coming back on topic, from a climbing point of view, a slightly stretchy harness on a soft-ish body, with a stretchy rope and a moving belayer all help to keep peak forces down...

What do you mean by “so-called lightweight” ? 

Everything is lightweight compared to original troll gear. To say it was built to last is an understatement. 

Ropes don't 'deteriorate with time.' (With use and abuse, maybe - but that's a different matter.)

There is an interesting post in Rock Climbing UK on Facebook where a Saul Cashmore claims his harness "snapped" while resting on it.

Seems a tad far fetched to me what do guys think??

https://m.facebook.com/groups/878960385489891?view=permalink&id=2727037...

Isn't the elasticity of a nylon rope supposed to deteriorate with age, even if it is stored and unused?

I've read a report saying the elasticity on an aged unused rope improved from new. The possible explanation was 'relaxation', a measure of alignment in the long chain polymers in the nylon. Reduced elasticity might be expected from cross-linking due to heat, chemical or UV damage,  but  might need a great deal if time to occur in their absence. Only a sample of one rope though In that article IIRC. But other articles that show elongation under load or even failed should give some data.

 > Ropes don't 'deteriorate with time.' (With use and abuse, maybe - but that's a different matter.) <

http://onrope1.com/myth-busters : "A rope loses about 2% of its strength per year even when it is kept in a like-new condition , even if it has never been used." However this is in a supplier's website and doesn't give any citation.

I'm not sure what definitive studies have been done, but I am very happy to be educated about it.

I guess an initial question is: does nylon itself spontaneously degrade over time?

Page 50 of the Tendon ropes workbook/catalogue.

Well i’ve retired my 12 year old mammut galaxy classic superdry with minimal use either way. Not worth the risk when it comes to safety! Rope manufacturers recommend retiring rope around the 3-5 year mark even if it hasn’t been used much and 10 years with no use. Read as much somewhere a few years back. Found this online: https://blog.weighmyrack.com/expected-lifespan-of-a-climbing-rope-aka-when-...

cant find an official manufacturer blurb atm though! Ps, happy new year everyone! 

Thanks for that.

For anybody else looking for it, a direct link is: https://www.mytendon.com/UserFiles/Image/1558706587katalog-tendon-2019-EN-w...

The info at page 50 onwards seems to have suffered a bit in the translation to English, unfortunately - I am struggling to understand the actual recommendations.

"An examination of the rope by a competent person (person authorized by the manufacturer) once every six months is mandatory."

Err, right! 

Anyone know of anyone authorised to make these examinations? 

This refers to professional use, where you'd send your company's stores manager on a PPE Inspection course that's approved by Tendon. 

Obviously nonsensical for us lot (rope access techs excluded), but it covers them legally.

Walter research or what the it was does not agree. They tested a bunch or ropes, and age was not the factor. Use & wear were. 
 

if interested, have a look around Facebook for them tests. 

Can you provide a link? Thanks.

https://www.facebook.com/SiebertResearch/

He's done some interesting tests.

thanks...

walter, close enough

The other factors that I have never seen evaluated is the effect of storing different types of soft materials together - what triggered this was storing a couple of dive masks and snorkels for approx 20 months in a dark, dry box... different brands and presumably different materials, one set came out fine, the other the was brittle and the snorkel essentially shattered. I've no idea the science behind this event but it has always made me think about the long term storage of ropes, harnesses etc.

IMO - if in the slightest doubt, destroy it. 

The evidence and references in this thread seem to agree with age being irrelevant, and in fact that's what I've thought. I did find that one statement from a supplier saying 2% annual strength loss but, as I said, it had no citation. Out of interest I've now emailed them asking for one and will post any useful response.

The ~25mm waist belt of my current lightweight Petzl is definitely the worst bit by a long shot, permanently bowed into a significant curve and quite furry where it goes through the buckles.

Waist belt (~50mm) went on my previous Petzl too, frayed ends and fuzz.

I don't suppose either are actually unsafe.

OP: I keep using them until I start to wonder.

jk

Static rope is still pretty bouncy, the peak load even abseiling badly should be trivial.

jk

Rubbers and silicones do have different aging characteristics from aramids and polyamides. Age related molecular cross-linking  ( the long chain molecules that deliver flexibility and elasticity link and join over time into shorter less flexible chemical isomers- the mechanism of "perishing") is a feature of natural and some synthetic rubbers, like diving gear and rubber tyres. UV, speeds the process, as does heat.

There is a fair amount of science of aging of materials, but often age alone  isn't the dominant factor.  Usage, storage, wear, number of falls, cleanliness, chemical contamination, manufacturing faults, all outweigh age, but sheer length of time increases the potential of exposure to most of these. So we'll always have a factor of ignorance to contend with, but in some cases that factor can legitimately  be reduced.

Harnesses are interesting cases because they aren't as simple as ropes and the failure modes are different. Designs differ in Buckles, belay loops and in redundant load paths (if any). If a harness - or how you tie in- has a single point failure mode I'd take that into account in the age/wear evaluation.

Walter is his given name.

I think I heard/read it somewhere. Hence the wrong cue.

Re: On Rope1 statement that there was a 25% annual loss in strength. 

Have received no citation about this from On Rope1 despite them copying in guy who made the statement on their website. Thus assume one can't be found.

OMG I hope you managed to recover those friends! Frigging expensive manufacturing defect otherwise haha! 🤪

Very true. It's usually the sudden stop at the end that kills you in a fall.

 Re: On Rope1 statement: "Age! A rope loses about 2% of its strength per year even when it is kept in a like-new condition , even if it has never been used." (Not 25% as I mistyped earlier).

The firm did reply to me with a reference: https://tinyurl.com/vbvu47shttps. However, unless I've misread it, this does not support their statement as it does not include testing unused old rope but only unused new rope.

Dead tinyurl link for me?

Try this. Original link works for me but tab comes up with this address (also works).

itrsonline.org/wordpress/wp-content/uploads/2016/11/Evans.Truebe_Strength-Loss-Due-To-Aging-of-1-Inch-Tubular-Nylon-Webbing-paper.pdf

The paper is for webbing rather than rope but presumably if wear isn't a factor any aging of unused nylon would be similar.

Climbing ropes haven't been rated or certified on their strength for over half a century and you won't find manufacturers strength listed anywhere so that's completely irrelevant.

I'm not at all knowledgeable on any of this, but aren't the UIAA ratings of ropes at least related to strength insofar as the rope stretches to reduce the force of a fall  so that it then easily supports body weight? However the strength of webbing presumably bears some relevance to safety of old harnesses as in the OP.

 So far I haven't seen anything which would directly answer the upthread question:  Does nylon itself spontaneously degrade over time? In fact everything would seem to point to it not doing so. Thus there appears to be no practical or theoretical evidence,for instance, that the replier who retired his 12 year old rope after minimal  use actually needed to do so.

The actual quote from the supplier does appear inaccurate and irrelevant, although maybe there are strength ratings for some of the ropes they provide as they supply arborists and rescue organizations as well as cavers and climbers.

One day but not yet, good luck I hope you outlast your gear.

Ditto, my indoor harness and outdoor harness are the same thing, it's 17 years old, the only sign of wear is the care label is now unreadable.

Nylon does degrade with time, moisture effects the ends of the chain bonds. There's an Australian Defence Dept report that mentions 20% loss in 15 years for nylon 6.6 parachute fabric in storage.

Thanks. I just googled and this might be a related reference, whichI think  includes thermally accelerated oxidation in nylon parachute lines. Past my bedtime so I haven't tried to understand it yet. Incidentally is that 20% a loss in tensile strength?

https://apps.dtic.mil/dtic/tr/fulltext/u2/a147698.pdf

Thanks.

Can anyone cite an example of a harness actually failing, other than Todd Skinner's?

Re:  https://apps.dtic.mil/dtic/tr/fulltext/u2/a147698.pdf

As far as I can understand it (eg don't understand the graphs involving log values) this reference appears to show that by extrapolation of temperature accelerated aging data nylon canopy repair material (ie unused) will degrade significantly in tensile strength over time. Much of the paper includes used data involving used parachutes. Probably not the paper Jim Titt mentioned however

Well it's not the same paper, that was a very technical one about the internal changes to the polymer chains and at a guess provided the basis for this papers calculations. The later graphs on strength loss in storage are easier to digest in this one

http://publications.americanalpineclub.org/articles/13197702102/Harness-Fai...

1977 report,  Some of details: A Mountain Safety Research climbing harness broke at the anchor point when the belayer caught a simulated leader fall at the Rock Climbing Sections safety tests.......with a carabiner joining his harness to a sling. .... he flew through the air as if propelled by a catapult. .... harness had parted where it went over the carabiner. The harness was made of MSR 2 inch black “Polypro,..... in two forms: either as a pre-sewn harness, or for the climber to tie his own...... harness was two years old, but had never suffered the shock of a fall, or any stress beyond being clipped to a chest loop in prusiking. His model was self-tied. Another belayer also holding simulated leader falls was wearing a pre-sewn model of the same material. Hers was partly torn by the end of the exercise (three “leader falls”)....

Failure due to acid on nylon

http://www.blackdiamondequipment.com/en/qc-lab-acid-harness.html?utm_medium...