New 2002 NEC requirements that may save lives someday!
440.65 Leakage Current Detection and Interruption (LCDI) and Arc Fault Circuit Interrupter (AFCI).
Single-phase cord-and-plug-connected room air conditioners shall be provided with factory-installed LCDI or AFCI protection.
The LCDI or AFCI protection shall be an integral part of the attachment plug or be located in the power supply cord within 300 mm (12 in.) of the attachment plug.
550.25 Arc-Fault Circuit-Interrupter Protection.
(A) Definition. Arc-fault circuit interrupters are defined in 210.12(A).
(B) Bedrooms of Mobile Homes and Manufactured Homes. All branch circuits that supply 125-volt, single-phase, 15- and 20-ampere outlets installed in bedrooms of mobile homes and manufactured homes shall be protected by arc-fault circuit interrupter(s).
We get asked this question at inspector meetings. The issue is one of ease of troubleshooting, isolating the cause, and not cutting off power to the whole home. If electricians had to try to find the fault by tracing each circuit, the technology would never be installed.