22 August 2006
Disability Glare the effect of stray light in the eye whereby visibility and visual
performance are reduced. A direct glare source that produces discomfort can also
produce disability glare by introducing a measurable amount of stray light in the eye.
Discomfort Glare glare that produces discomfort. It does not necessarily interfere
with visual performance or visibility.
Downlight a small direct lighting unit that directs the light downward and can be
recessed, surface-mounted, or suspended.
Efficacy See luminous efficacy of a source of light.
Efficiency See luminaire efficiency.
Electroluminescence the emission of light from a phosphor excited by an
Emergency Exit a way out of the premises that is intended to be used only during an
Emergency Lighting lighting designed
to supply illumination essential
to the safety
life and property in the event of a failure of the normal supply. The system must be
capable of providing minimum required illuminance specified in NFPA 101, Code for
Safety to Life from Fire in Buildings and Structures, Section 5.9.
Exit sign a graphic device including words or symbols that indicates or identifies an
escape route or the location of, or direct to, an exit or emergency exit.
Floodlight a projector designed for lighting a scene or object to a luminance
considerably greater than it surroundings.
Fluorescent lamp a low pressure mercury electric-discharge lamp in which a
fluorescing coating (phosphor) transforms some of the UV energy generated by the
discharge into light.
Flush-mounted or Recessed Luminaire
a luminaire that
is mounted above the
ceiling (or behind a wall or other surface) with the opening of the luminaire level with the
Footcandle, fc a unit of illuminance equal to 1 lm/ft.
Glare the sensation produced by luminances within the visual field that are sufficiently
greater than the luminance to which the eyes are adapted, which causes annoyance,
discomfort, or loss in visual performance, and visibility.
Globe a transparent or diffusing enclosure intended to protect a lamp, to diffuse and
redirect its light, or to change the color of the light.
High-Intensity discharge (HID) Lamp an electric-discharge lamp in which the light-
producing arc is stabilized by bulb wall temperature, and the arc tube has a bulb wall
loading in excess of 3 W/cm. HID lamps include groups of lamps known as mercury,
metal halide, and high pressure sodium.
High-Mast Lighting illumination
of a large area
of a group
that are designed to be mounted in a fixed orientation at the top of a high mast,