system
Given the following post, respond as if you're commenting on Reddit:
human
Will being near a large particle accelerator such as the LHC cause a magnetic compass to drift from true north?

If I am walking near the LHC on the surface how close would I have to be for my magnetic compass to drift an appreciable amount due to the strong magnetic field?
gpt
Accelerator facilities often use strong magnets to steer and focus their particle beams. These magnets will in general have fringe fields when they're turned on and ramped up to a significant current. If you come within the range of the fringe field, you will see magnetic effects such as deflection of compasses, distortion of CRT screens or other electronics, erasure of credit card strips, etc. You shouldn't be near them if you have a pacemaker.

The magnets used in these facilities are mostly dipoles and quadrupoles, so their fields drop off as 1/(distance)^(3) and 1/(distance)^(4) respectively. Often they'll have some magnetic shielding around them or additional coils to minimize fringe fields, so the ranges will probably be even shorter in practice.

In other words you need to be pretty close to the magnet for these things to happen.