The strongest glow is produced during the first 30 minutes of darkness, the most critical period following a power failure or other emergency. During the period of darkness, the eye of an average person will adapt to the darkness at a rate roughly matching the decrease in luminous intensity of Glo-lite, thus enabling vision to continue for may hours. Glo - lite products are correctly termed luminescent or photoluminescent. The term phosphorence is sometimes used to describe luminescence, but Glo - lite materials contain no phosphorus. Luminous materials differ from reflective materials, which amplify and increase relative brightness when light is applied.
Luminous materials require prior exposure to a light source in order to glow in the dark.
When the source of light suddenly goes off, Glo - lite photoluminescent materials glow strongly. After an initial decline in brightness, the glow settles to a near continual intensity. A positive life-saver during the evacuation of buildings, in the case of fire, or other sudden emergencies. When bright lights are suddenly switched off, the human eye detects almost nothing, but then begins to adjust to the gloom. The below illustration demonstrates this rate of adjustment to detecting indiscernible objects.