rolling20 indicated the DC-6 fire was caused by a faulty cabin heater.
A series of in-flight fires (including the fatal crash of United Airlines flight 608) grounded the DC-6 fleet in 1947. The cause was found to be a fuel vent next to the cabin cooling turbine intake; all DC-6's were modified and the fleet was flying again after four months on the ground.
Also, note the 24 Canadair Northstars allocated to the RCAF were unpressurised and had round passenger windows.
Last edited by evansb; 26th Jan 2021 at 17:23.
Reason: adding information regarding unpressurised Northstars.