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13 Exit Signs
- Most exit signs are approximately 12” long, 8” high and between
1” and 4” in depth.
Types of Signs
There are two types of exit signs:
- externally lit (rare)
- internally lit (most common).
- An external light is aimed on the sign.
- Bulb replacement is easy.
- Sign is difficult to see in smoky conditions.
- Power consumption is high (generally incandescent lamps are used).
- Single– or double–sided sign with light source inside the fixture.
- Some exit signs have an opening fitted with a diffractive lens at the bottom to help light the exit route.
Light Sources of Internally Lit Signs
There are four light sources for internally lit exit signs:
- Incandescent lamps
- Compact fluorescent lamps
- Low–voltage lamps: LED and miniature incandescent lamps
- Tritium gas
- LED (light emitting diode) type sign has LEDs in plastic tubes which form the letters.
- These signs use plastic as the medium to transmit the light.
- Require less depth than incandescent and compact fluorescent signs.
- More uniform illumination of letters.
- Manufacturers expect 10– to 15–year lamp life.
- Consumes approximately 2 to 3 watts of power.
Compact Fluorescent Signs
- More expensive than incandescent signs.
- Most incandescent exit signs can be retrofitted with compact fluorescent if there is sufficient space inside the sign to accommodate the lamp and the ballast, although this has become an unusual practice due to the efficiency of LED retrofit units.
Compact Fluorescent Lamp Retrofit Lamp
Compact Fluorescent Lamp – Hard–Wired
- Compact fluorescent lamps of 5, 7 and 9 watts provide lighting levels similar to incandescent lamps of 25, 40 and 60 watts respectively.
- Lighting of each letter is not uniform.
- Lamp life is generally one to two years.
- Consumes approximately 12 to 20 watts.
Tritium Gas Signs
- Illumination principle is similar to that of a television.
- Radioactive tritium gas undergoes beta decay, releasing an electron which is incident on a phosphor–coated tube, shaped into the word EXIT
- A modern tritium exit sign uses 25 curies (about 2.5 milligrams of tritium in the gaseous form).
- No external energy source required.
- Lamp life is 10 to 20 years; it must then be replaced.
- Highest capital cost for lamp and fixture.
Existing incandescent signs should be immediately replaced because of cost of operation and in commercial and industrial applications cost of maintenance.
- Can no longer be purchased in Canada.
- Incandescent signs usually have two 15 to 25 watt bulbs.
- During a power failure, a sign may be energized by either the emergency power supply system or a 12 V bulb in the middle of the sign powered by a battery.
- Cost varies due to construction features such as vandal–proofing, internal battery etc., and aesthetic features.
- Incandescent signs were the most common type of exit sign in the past.
- Lighting of each letter is not uniform.
- Bulb life is generally one to six months.
- Consumes approximately 30 to 50 watts of power.
- The National Building Code of Canada requires that:
"Lettering on exit signs shall be:
- red letters on a contrasting background or white letters on a red background, at least 114 mm high with 19 mm stroke spelling EXIT or SORTIE when the sign is internally illuminated, and
- white letters on a red background or red letters on a white background at least 150 mm in height with 19 mm stroke spelling EXIT or SORTIE when the sign is externally illuminated."
"The lighting for exit signs shall:
- be supplied by an electrical circuit that
- is separate from the other circuits, or
- serves other emergency equipment, and
- be connected to an emergency power supply..."
- The National Fire Protection Association of the United States requires the exit signs “... be illuminated by not less than 5 foot candles (54 lx) and shall employ a contrast ratio of not less than 0.5”.
This is not a requirement in Canada.
Note: Check local codes for requirements in your area.
- Incandescents are inexpensive to purchase but expensive to operate and maintain.
- Compact fluorescents can be retrofitted into most incandescent fixtures to reduce energy and maintenance costs.
- LED signs consume less electricity and provide more uniform illumination, as well as being more aesthetically pleasing.
- Tritium gas signs do not consume electricity. The energy comes from the radioactive decay of tritium. They have a high initial cost but require very little maintenance.
- The energy efficiency of Exit Signs are now regulated in Canada and LED technology is the only one able to meet these performance levels.