They spoke out after the landlord of a lodging house in Don Road risked his own safety believing someone was trapped inside.
He went back into the building after the fire alarm went off at around 7.20 pm yesterday.
Although the man suffered only smoke inhalation, sub-officer Jason Masterman said he could easily have become the victim.
Ten people had to be evacuated from the lodging house after a plastic container left on an oven hob caught fire, but there were fears someone was still trapped inside.
The landlord entered the flat and checked to see whether it was empty, which it was, and then went in a second time to tackle the flames.