Electronics/ magnets. Patients with pacemakers are advised to avoid strong magnetic fields. Mri studies are generally contraindicated. Electronic devices such a cell phones and game controllers should usually be kept at least 12 inches away fom the device. Security devices can sometimes cause problems and many airports will have pacemaker patients have a different assessment.
Electrical noise. Electrical noise such as an old leaky microwave oven while it's on if the person is standing very close to it.