The biggest problem[citation needed] was that the exit sign was hardly distinguishable from an ordinary safety lighting fixture commonly installed above doors in the past.
Under normal conditions, the exit sign was lit by mains power and the battery was maintained in a charged state.
While exit signs were more visible due to large letters, even a 60-watt incandescent bulb shining through a plastic or glass cover could appear somewhat dim under certain conditions.
With the development of fluorescent lamp and light-emitting diode technology, exit signs could be made even brighter to compensate for the limited visibility in a fire situation, while using less electricity.
Radio-luminescence uses the radioactive decay of tritium gas to illuminate the sign,[5] while phosphorescence uses light-emitting pigments to glow in the dark.
Most exit signs in the world, except in countries such as the United States, Canada, Hong Kong, Philippines, and Singapore, use pictograms.
In the United States, the National Fire Protection Association (NFPA) defines the standard for exit signs.
[9] Newer Airbus, Bombardier CS100, and Boeing 787 Dreamliner planes use the new pictogram exit signs, which were approved by the FAA in 2012 and 2014 (depending on aircraft type).
Parts of the Corning Museum of Glass use an exclusive variant of the ISO pictogram, pointing to exits, along with textual signs.
The signs often have metal or plastic knock-outs which can optionally be removed so that an arrow is also lit pointing left or right.
Modern exit signs are often combined with other safety devices, such as emergency floodlighting for supplementary area illumination.
Exit signs draw a relatively small amount of power, and can generally be added onto any existing electrical circuit without adverse effects.
[citation needed] It is often a serious offence for a building owner or landlord to not comply with the fire/building code in terms of Exit signage.
New York City, Rhode Island, and Chicago (along with the rest of Illinois) require that exit signs be red.
Most Canadian jurisdictions require the international green "running-man" pictogram; however, some have allowed red "EXIT" signs to be maintained in older properties so long as one style is used consistently throughout the building.
[21] Green fluorescent signs can be seen better in dark conditions than other colours, as the human rod cell is more sensitive to these wavelengths.
Advocates propose that appropriate exit signage to identify the accessible means of egress is a critical component to successful emergency planning for any building.
[27] The concept also provides more intuitive building design to assist people that are blind or have low vision to locate an exit.