Do big aircraft (e.g. Boeing 737 or Airbus 320) have carbon monoxide (CO) detectors installed in them? I don't know if the pressurized cabin means they aren't needed, but I do remember there are CO detectors in small planes and there are some reported accidents due to inhaling CO from engines.
Haven't seen any. Cabin heating is done quite differently on jet aircraft than on pistons. Bleed air is taken from the engine before the combustion chamber, so engine exhaust can't end up in the cabin, even if there was a greater fault in the A/C packs.