How is smoke detected in the cabin when flying without passengers? The Boeing website states that smoke detection devices are not present in the passenger cabin as the passengers/cabin crew are able to detect the smoke:


  A dedicated smoke detection system is not required in the occupied volumes of the main cabin due to the ability of passengers and the cabin crew to recognize smoke.


How would smoke be detected in the cabin when flying without passengers or cabin crew? As an example, this could be the case on a ferry flight where no one in the cabin may be present to detect smoke.
The threat for a cabin compartment smoke or fire comes from paying passengers &amp; baggage.
On a ferry flight, you have neither, so the threat is greatly reduced or eliminated.
The FAA authorizes ferry permits for only 1 or a few  segments to get an aircraft to a facility where maintenance can be performed, these ferry permits take into account the risks involved and thus why no revenue cargo / passengers can be carried.