Was My Hotel Bonkers?
May 18, 2019 5:23 PM   Subscribe

My hotel in Chicago claimed that my no-longer-functioning room key was "Demagnetized" by being placed next to a credit card. I did not believe it. Do any of you believe it?
posted by Raybun to Technology (34 answers total) 2 users marked this as a favorite
 
Yeah, I believe this used to happen pretty frequently with hotel keys actually (perhaps not actually magnetized, but deactivated, yes)
posted by raccoon409 at 5:27 PM on May 18 [2 favorites]




No I don't believe it. From yisyiwy's article:
Some people believe that having one credit card next to another can cause them to become demagnetized. The theory behind this is that magnets cause demagnetization of magnetic stripes, and since magnetic stripes are in fact magnetized, this magnetic energy can cause another magnetic stripe to demagnetize. This is far from the truth however, and it would take an unprecedented amount of exposure for this to occur. Furthermore, the cards would have to be strip-to-strip for this entire time, and there's still little to no chance of the demagnetization process occurring.
posted by Reverend John at 5:50 PM on May 18 [4 favorites]


but that link actually says it's unlikely? "This is far from the truth however, and it would take an unprecedented amount of exposure for this to occur. Furthermore, the cards would have to be strip-to-strip for this entire time, and there's still little to no chance of the demagnetization process occurring." it was probably physical damage, apparently? like a scratch to the surface of the strip from being in your pocket with keys.
posted by poffin boffin at 5:51 PM on May 18 [1 favorite]


I also do not believe it for the reasons stated in the article. Also, (and granted, this is just one personal experience) I was at a wedding recently where we all left together from the hotel and returned together on a rented bus at about 11:30 PM. Almost none of our card keys worked. We all had to show our IDs to security and they "reactivated them". I find it much more likely that they were concerned about inebriation or non-guests arriving with the crowd. FWIW.
posted by forthright at 5:56 PM on May 18 [3 favorites]


The card was carried in my wallet and was only in contact with paper
posted by Raybun at 5:57 PM on May 18


More likely to be from your phone
posted by mikek at 5:57 PM on May 18 [5 favorites]


Forthright ; I was sober and non-confrontational
posted by Raybun at 5:58 PM on May 18 [1 favorite]


Mitek; No phone
posted by Raybun at 5:59 PM on May 18


I have had this happen under a wide variety of circumstances and my best theories are these: these cards are cheaply bulk-produced and don't "hold" their encoding very well, or the keycard programming system is sort of crap and the locks forget/lose network contact/malfunction/get wiped pretty frequently in certain establishments.
posted by Lyn Never at 6:06 PM on May 18 [49 favorites]


It may have stopped functioning as a result of being "demagnetized". What's certain is that this was neither due to being in proximity to a magstripe payment card nor in any way your responsibility.
posted by turkeyphant at 6:09 PM on May 18 [8 favorites]


I've been at hotels where simply because I took my baggage with me during the day they assumed I'd left, in contradiction of my reservation, and gave my room to someone else. On one occasion at least they didn't deactive my key card and so at the end of the day I came back and walked right into a room full of people who were as surprised as I was.

So I think hotels very aggressively jump the gun selling rooms when they think they can, or perhaps just do it out of incompetence, and make up tall tales like this to cover their asses.
posted by XMLicious at 6:11 PM on May 18 [6 favorites]


hahahahahaha no your card did not get demagnetized by another mag stripe. Something that puts out a field many, many orders of magnitude stronger could have, but you're not likely coming in contact with such a field anyway.

Anecdotally, too, I've never had a magstripe credit card cease working, but have had hotel key cards die many times.
posted by MillMan at 6:13 PM on May 18 [4 favorites]


I believe that the demagnetization thing is a convenient lie to cover many failure points, including all the things other folks here have talked about. I don't believe that demagnetization is the culprit. Per the article yes I said yes I will Yes posted, I think if there is any technical issue that actually affects the keys it's physical damage, not electromagnetic.

Also, some cards now do not use magnetic stripes, but induction or RF-based tags, and those can be killed by certain kinds of physical shocks (crushing, generally, but sometimes physical strikes). I think situations that generate these forces are rare, but also kind of inexplicable.
posted by kalessin at 6:16 PM on May 18 [3 favorites]


kalessin; This was an RF card
posted by Raybun at 6:26 PM on May 18


If this was a contact-based RF card, magnetism is not how it works in the first place. They repurposed their old slightly plausible excuse for the old magstripe-based tech without checking if it's still valid, which it isn't.
posted by Aleyn at 6:33 PM on May 18 [28 favorites]


A more likely explanation is that they keyed in the wrong departure date for the key or some other glitch in the system.
posted by jzb at 6:47 PM on May 18 [5 favorites]


Yeah RF cards are totally different and while they are wrong on the physical nature of the mechanism, there are a zillion ways they can fail, one of which is getting crunched up in a wallet and sat upon. Usually that is fine, but sometimes it’s not, just a matter of angles and pressure and luck.
posted by SaltySalticid at 6:52 PM on May 18 [2 favorites]


Your hotel did not tell you this. An employee at your hotel told you this. That employee probably heard the explanation from other employees who decided it was the easiest thing to say to people in the face of crappy key cards failing frequently.
posted by Winnie the Proust at 7:27 PM on May 18 [41 favorites]


This has happened to me multiple times, and there was never any reason to suspect it was for nefarious or sneaky reasons on the part of the desk workers, it's just that this technology sucks and fails all the time. "Demagnitized" is probably what they said because that's what they said for the first generation of magnet stripe keys and then just kept saying it.

For the record, there is something called a Clipper card that you use to store your mass transit fare in the bay area and the official advice is not to store it near any other RFID type cards because they interfere with each other, so it's not like there's not a legit precedent for this kind of advice.

The card reader may not have recognized your card for one of several reasons. Try tagging your card again by holding it flat against the Clipper logo on the card reader until you hear it beep. If your card is stored in your wallet or near chip-based cards that use radio frequency information, please remove it and tag it separately to the card reader.
posted by bleep at 8:23 PM on May 18


not to store it near any other RFID type cards because they interfere with each other,

But this isn't because it causes the card to stop working. It's because the tag reading device can't distinguish the two cards if they are both nearby.

What people above are saying about crushing or other damage causing an RF card to fail is correct but I think in that case the chip is dead, so they couldn't just reprogram it and have it work again. If that's what they did, then it's some other (weird) cause. But either way, it's nothing to do with demagnetisation.
posted by lollusc at 8:40 PM on May 18 [2 favorites]


My wife, a former front desk manager at Marriot's exclusive Rennaisance hotels, tells me that Lyn Never's comment is the most true. And I believe that Winnie the Proust identified the most probably reason why you were told this.
posted by seasparrow at 8:42 PM on May 18 [3 favorites]


I'm just saying there's a jumbled up mix of things people generally know about these types of cards (the new ones can't be near each other for similar but different reasons that the old cards can't be near each other) which is probably why the term given wasn't exactly correct.
posted by bleep at 8:44 PM on May 18


these cards are cheaply bulk-produced and don't "hold" their encoding very well, or the keycard programming system is sort of crap and the locks forget/lose network contact/malfunction/get wiped pretty frequently in certain establishments.

This is decidedly the case. I work in hotels and key cards regularly fail for no clear reason even immediately after programming them, something most common with new batches of cards.

Why do we tell people they were "demagnetized"? Because people want a reason and can be jerks if they don't get one or get one they don't like. Putting it off on the mysteries of magnets tends to satisfy people more than saying the cards are cheap and the tech imperfect and maybe something unknown did cause the stripe to fail. It's a quick answer and generally serves the needed purpose. We don't like having to reprogram cards and deal with the situation anymore than the guest, so the goal is to get the process over with as quickly and simply as possible. I'm also sure many desk clerks themselves believe the answer and just relay it for hearing it said before and not having any better idea of why any given card fails.
posted by gusottertrout at 9:50 PM on May 18 [16 favorites]


RFID key cards are passive devices. They require a magnetic field from a reader to induce a current in their internal circuit (like a wireless charging pad). It then emits an RF signal that is read by whatever wants to read it. Having two passive devices near each other should not do anything,
good or bad. Mechanical damage to the RFID circuit is much more likely, or interaction with any number of magnetic field generators that we encounter on a daily basis. Also tags are thermally sensitive. I know of a production tracing application where RFID tags that passed through an oven were not readable at temperature, but were readable again once again once they cooled down. Granted this was about 300F, but it was interesting that the process is reversible.

Yeah, they're almost definitely full of shit, but RFID technology is pretty neat!
posted by dudemanlives at 9:51 PM on May 18


Here is a page which talks about some of the potential sources of unreliability in RFID cards. (they also explain how the technology works on some related links). The page mentions a number of issues which are listed by others above - and some which are not directly - including the following:
1. There is no one single RFID standard. Different manufacturers (the most prominent in this case being RFID Hote - who boast about their "reliability" rates - but provide no details - and who can't even protect their site with HTTPs) come up with cards and readers which work well with each other - but they don't test for the presence of other cards and readers from their competitors that may be present at the same time. If the reader tries to get information from just one card - but receives responses from several - it can cause the ID transaction to fail.
2. The card/reader information display uses the same electromagnetic spectrum as a range of devices such as WiFi or cell phones. Whilst it is certainly not true that your card might have become demagnetized by your cell phone - it is possible that activity on your phone, or a nearby router, or a neighbour's phone - as you tried to get into your room, could have messed things up.

As others have pointed out, the rate of failure for these kinds of cards seems to be amazingly high. On a 5 day visit to a hotel with this type of card, my experience is that I will need to get the card changed once. If we assume I have 4 key transactions per day then that means the failure rate is about 5%. This seems to be bourne out be the other commenters here. But that unreliability may not hurt the hotel as much as one might think: they are probably delighted with any system that is more cost effective than the old physical keys that people would walk off with all the time, they have somebody on reception anyway, and the card can be replaced in a few seconds by somebody with a little training.

Finally - be aware that there are 2 types of RFID technology being used in Hotel Locks: 125KHz and 13.56MHz. The latter is newer and more reliable than the former - but more expensive!
posted by rongorongo at 12:12 AM on May 19 [5 favorites]


Do any of you believe it?

Of course I do. Which is exactly why I will never drive into a service station that has those new fangled pay-in-line fuel pumps in case the intense magnetism off somebody's credit card causes a spark that sets off a huge explosion.

Seriously though, it's total bullshit and the fact that so many people think this way reflects the fact that physics is simply not taught properly any more.
posted by flabdablet at 1:05 AM on May 19


I’ve stayed at a decent number of hotels where I never had a problem with the key cards, and a few hotels where I kept having problems with the key cards - including my wedding, where they failed multiple times a day for various rooms. The hotel staff at places they failed always re-made the cards when asked, and clearly have it happen regularly. I don’t know why you would assume malice - incompetence perhaps (we once had someone check the next person into our room number instead of the once next door, so they walked in on us and we had to get our cards re-activated - 100% incompétence which they made up for with food/bev vouchers at the attached cafe).
posted by DoubleLune at 6:34 AM on May 19


Sure. Here's the science.

Hahaha and apologies for posting without proofing. The word science was meant to be in quotes because like the article notes, no, this is not a thing.
posted by yes I said yes I will Yes at 6:45 AM on May 19 [2 favorites]


Sorry Raybun, I didn't mean to imply you were inebriated or acted oddly, I just meant that in my situation a whole bus full of people coming in from a wedding, I could somewhat see them giving a bogus explanation as a way to get us to show our ID before "reactivating" the cards. I am not in the hotel industry, so my experience could just be a one off and I'm guessing at the back story.
posted by forthright at 12:32 PM on May 19


I have a rule of thumb about desk clerks and gate agents that seems pretty reliable. They always lie, either because they’re told to by their employer or because it’s the easiest way to slide through their interactions with you. The take away from this is you should never even consider whether an explanation is right or not, you should only ask “did I get what I needed from this interaction?”

Desk clerks: your key was demagnetized. Gate agents: it’s a weather delay. Me: “did I get into the room/onto a different flight?”
posted by Gilgamesh's Chauffeur at 12:52 PM on May 19 [1 favorite]


They always lie, either because they’re told to by their employer or because it’s the easiest way to slide through their interactions with you.

That's more or less right, though I sorta object to the idea we always lie, more that relaying the least necessary information to obtain the needed end result is preferred. Adding information adds likelihood of further complication and complaint as that extra information provides more opportunity for conflict. Clerks mostly aren't given leeway to argue with guests/customers, so the goal is to remove as much non-essential possibility for argument as one can to maintain focus on fixing the problem as efficiently as possible.

That and clerks often don't have all the information to give an "honest" answer, they likely don't know why a key card doesn't work really, or why your computer can't connect to the internet or all the background about why a flight is delayed, just that something isn't working as it should and they have to deal with the people who are going to be annoyed by that.

It is true though that there are time they do know what's wrong, they may indeed lie for being familiar with systems customers often are not. Saying something doesn't work for the true reason can lead to people thinking those reasons are a more significant or uncommon sets of problem than they actually are. Trying to explain the internal workings of an industry to an outsider is just not worth the effort most of the time.
posted by gusottertrout at 2:38 PM on May 19 [2 favorites]


Nope. Not true.

I've stayed in 100's of hotels since electronic keys were introduced. When the card doesn't it work, it's because:

It wasn't "swiped" properly to enter the room data (room #, checkout date)

The data above was entered wrong.

The card has been used too often, abused or made so cheaply that the above data is corrupted.

Hotel desk staff may have wrong ideas about why the card doesn't work. Just politely ignore their reasons and get a new card, even if it is a hassle (says the guy who has too many times dragged a dog, a laptop bag and a suitcase to a room, only to have to drag all of them back to the lobby for a working card.)

My favorite example, from when a buddy and I were in Mexico. We have about 4000 hotel nights around the world between us.

CLERK: You put it next to your credit cards.

US: We aren't carrying credit cards. you are an all-inclusive resort.

CLERK: You put the card next to Mexican coins.

US: We aren't carrying coins, you are an all-inclusive resort.

CLERK: You got the card wet in the swimming pool or ocean.

US: We kind of suck at golf, but we weren't swimming to find lost golf balls.

CLERK: Sometimes the moon phase.
posted by ITravelMontana at 7:11 PM on May 19 [1 favorite]


Bonafides first: I'm a Quality Manger at the largest manufacturer of hotel keycards and giftcards in the US. I see every aspect of this discussion every day.

Magstripe cards: Yes, the magnetization on one card can affect the magnetization of another under special circumstances, particularly if one is what we call a Hico and one is a Loco and they are placed back-to-back (stripe-to-stripe). Magstripe cards typically have one of three "strengths" (coercivity) commonly called low, medium, and high. Low has a coercivity of around 300 oersted. medium in the 700 range (it's the oddball of the three) and high is around 2750, or 10 times stronger than the low. Generally speaking hotel keycards are low (low magstripe is cheaper) and giftcards and creditcards are high (you don't want them to lose their encoding). Also generally speaking hotel cards and gift cards use different "tracks" in the stripe so they won't generally "line up" when put against each other. Bottom line is that card-to-card interactions can happen, but that is almost never the explanation for a stripe card not working.

I regularly test cards returned from the field that have failed at hotels and they almost without exception have bad encoding that resulted in the issues. And that bad encoding is usually the fault of the encoding hardware at the hotel being old, unmaintained, dirty, etc. with occasional user issues. If they have been demagnetized I can tell, but I can't tell what did it.

RFID cards: There are a plethora of contactless RFID access card technologies. The two frequency ranges were mentioned however the higher range is typically used at hotels where the cards are used by different people and the lower 125k range is used in access applications where one person keeps the same key - like an employee badge that also allows access. The hotel-access cards are actually cheaper as the low-frequency "Prox" cards have to be specially encoded to work at a particular location).

RFIDs are extremely durable; you probably will not ruin one by crushing or bending. During manufacturing, these cards are subject to a 20-minute lamination cycle that heats them to 270 degrees F and over 1000 pounds of compression. You could possible mess them up by bending them over a very short radius, but they are pretty tough. They are totally passive and not subject to stray EM fields. As for the multiple-cards-at-once not reading: maybe. I have test equipment that can read each unique tag in a stack up to about 5 cards if they area fanned correctly, but for some RFID types two together will interfere with each other and not read.

I'll agree that the front-desk people may not be the best-informed when it comes to diagnosing problems, however I know that in some cases the encoding software that they are using actually reverts back to old Mag Stripe Error Messages even when they experience failing RFIDs, so their software isn't helping them.

I hate trying to diagnose an issue where RFIDs are failing in the field because there are so many variables and the issues are often not reproducible, but if they properly encode then any subsequent problem is due to systems with which they are interacting, not the cards themselves.

So, your RFID card wasn't demagnetized, nor was it likely damaged in any way. There's nothing in your wallet nor any normal environment that affected the encoding, it's most likely that it wasn't encoded properly in the first place.
posted by achrise at 10:09 AM on May 20 [10 favorites]


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