Info needed for research. Thanks to everyone who answers

Per A. Dean Sherry, chemistry professor at the University of Texas at Dallas, associate director of the Rogers Nuclear Magnetic Resonance Center, and radiology professor at the university's Southwestern Medical Center, it isn't the power of the magnet; it's exposure time. "The field strength isn't all that important," he said. "Even a refrigerator magnet should work eventually. It is well known that magnets will wipe out information on credit card stripes. However, it doesn't always happen after one exposure. It may take several exposures for the card to be deactivated, but it will happen eventually."
Wasn't hard to find several sites about this. You might want to read about the different types of cards these days, such as smart cards, because they contain a chip.
Try 'magnetic stripe card' on wikipedia.

My father went through an MRI with his wallet once, and lost all his card stripes.

Magnets can deactivate the magnetic strip on a bank/credit card given enough exposure.

[This] link was helpful for me.

Why not research ? Get a local bank or other location to agree to help.
Even other places that use cards for ID and doors.
Set up difference magnetic fields, and expose to strength and time differences.
Then you can do a study of many cards and determine the effects.

If you really want research what about doing a project to determine.

One of the advantages of the new cards with embedded chips is this problem goes away.

Quote:

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Originally Posted by ebaines

One of the advantages of the new cards with embedded chips is this problem goes away.

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Assuming the chip still works...

When I check into a hotel I am frequently told to keep the door cards away from my phone. I have had to have the cards reprogrammed after putting it to near the phone.

Quote:

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Originally Posted by ScottGem

When I check into a hotel I am frequently told to keep the door cards away from my phone. I have had to have the cards reprogrammed after putting it to near the phone.

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I've had the sane experience - but it turns out that the type of cards used for hotel key cards are much less robust in terms of standing up to magnetic fields than the material used with credit cards. Also if you have the experience of your key card working one day but not the next this article says it's more likely faulty coding on the part of the hotel staff when you checked in:

http://www.secureidnews.com/news-ite...otel-key-card/