Preventable Fire Stories

• Smoke doesn’t always rise, particularly early stage smoldering where there is not as much heat to lift the smoke to the ceiling. Smoke moves more randomly then.
• My power strip can be a secondary detector placed much closer to the source of smoldering, providing an earlier warning
• Smoke does have a tendency to rise so most installations of the smoke detecting power strip should be above the appliances being protected. However, airflows in the room should be considered from heating systems, air conditioners, fans, and other factors.
• High ceilings can trap a layer of warm air that prevents smoke from reaching ceiling mounted protectors.  That’s why my power strip can be a good secondary point detector:

Takeyoshi Tanaka, Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, Japan says

A hot upper layer pre-established under the ceiling of a room in a house due to a solar load in the summer or room heating in the winter may cause problems for fire detection by ceiling-mounted smoke detectors. A weak plume from a smoldering fire may be pushed back down by the hot layer, and be unable to reach a ceiling-mounted detector. LINK

Peter Fox of Airsense Technology

It was recognised many years ago that the relatively cool smoke produced by the early stage of electrically initiated fires travels on the air currents generated by the air conditioning system, rather than being able to rise by thermal buoyancy to the ceiling, where conventional type smoke detectors are installed. …

Primary detection offers an extremely efficient method of protecting an area subject to high air movement. But if the air handling system is switched off, detection will suffer – any smoke will rise to the ceiling in the normal way. Consideration should therefore be given to installing secondary detection either through conventional point detectors… LINK

says:
early smoke does not always rise to reach ceiling-mounted detectors, especially in large open spaces with high ceilings. In historic structures, early detection is critical to avoid extensive damage or destruction of a significant building and its contents, in addition to the life safety concerns.

Fire must be detected early in the smoldering, incipient stage before active flaming occurs. Once flames have occurred it is too late, serious damage will occur from the flames and then from the water used to extinguish the fire. (LINK)