Could a compass be demagnetized in a tunnel?

Question

Since I passed a long tunnel, my compass doesn't work anymore! What's the reason.

Important: It already happened 2 times.

Answer 1

actually, it may have been re not de magnetized. There may have been some magnetic rock in the walls of the tunnel, or electrical conduits with wires inside generating their own somewhat strong magnetic fields. Too much exposure could have affected the metal inside the compass, if it is a simple compass. If it is something like a gyro compass, go get it recalibrated.

Answer 2

If u come closet to very powerful ac cables it will demagnetize the needle.