2. How do artificial lights work?
Metal halide lamps can pose a risk if used close to the
skin, but they are not intended for that.
Fire has long been the only source of artificial light and
today still, a large portion of the world’s population uses fire
as their primary light source. Humans discovered fire early on
in their history and used burning or heated materials as light
sources. Today, approximately 1.6 billion people still use
The first electrical light sources were also based on heating
a substance until it glowed and this is how incandescent
lightbulbs (carbon or tungsten) work. Halogen lamps are a modern
type of incandescent source where the tungsten filament is
contained inside a tube filled with a mixture of gases. One of
the gases is a halogen and allows the tungsten to get very hot
without melting. This makes the lamp more efficient and
long-lasting and the light is brighter and closer to the colour
of daylight, which is better for vision.
When electrical current flows through a gas, it can emit
visible light and
this process is used to make electrical discharge lamps. The
basic design is a tube filled with gas and with an electrode at
either end so that an electric arc can be sent between them. The
actual light emitted depends on the pressure and the nature of
the gas. Low pressure discharge lamps are very efficient but
some models are bad at showing the natural colours of objects,
as is the case for the yellow sodium lamps sometimes used for
Fluorescent lamps are a
specific type of low-pressure lamps where the
visible light is
produced by the phosphorous coating inside the tube that glows
in response to the intense UV-light produced by the
inside. Fluorescent lamps are cheap, long-lasting, efficient and
very good for illumination.
lamps (CFLs) consist of two, four or six small
fluorescent tubes mounted on a base. They are very efficient and
work in a similar way to conventional fluorescent lamps.
High-pressure gas discharge lamps produce intense light. They
are used in very specific applications and rarely in
conventional indoor lighting. Flash lamps are designed to
produce bursts of extremely intense light and are used mostly in
photography, scientific, medical and industrial applications.
Dielectric-barrier discharge lamps are also used in industry.
Solid state lighting is a new technology that could become
dominant in future:
- Light-emitting diodes produce light by a process
called electroluminescence. Although LEDs are coloured, it
is possible to combine several LEDs to produce white light.
Today, low-power LEDs are used for signs, indicators and
Christmas lights. High-power LEDs are used for lighting.
- Organic light emitting diodes produce flat panel
displays with brightness and sharpness that is impossible to
achieve in any other way, but this technology is still in
the early stages.
- Field emission devices are based on the same principle
as the luminescent material used in TV screens. These lamps
are 4 to 5 times more efficient than existing lamps, do not
contain hazardous materials, have long life spans and can be
made to produce light similar to daylight. This technology
is still at the experimental stage but expected uses are
indoor lighting and projectors.
It is difficult to pinpoint the “typical” spectrum emitted by
a type of lamp because individual designs vary. It is for this
reason that each individual model of lamp needs to be classified
according to the specific risks posed to health. This
classification is made according to a number of health effects,
as four risk groups (RG):
- RG0 (exempt from risk) and
- RG1 (minor risk) lamps are not hazardous during normal
- RG2 (medium risk) lamps do not pose hazards because we
naturally move away from lights which are too bright or too
- RG3 (high risk) include only lamps where a short-term
exposure poses a hazard.
This classification is based on short-term exposures responses
and applies only to individuals of normal sensitivity.
The majority of lamps used for normal lighting conditions are
RG0 and most of the rare exceptions are RG1. Provided that these
lamps are used at the distances for which they were intended,
the UV, IR or blue light radiation they emit should pose little
or no risk to non-photosensitive people. Halogen lamps are
intended to be used with an external glass filter and they
should also be non-hazardous, provided the filter is actually