Light and radiation
By light we mean the part of electromagnetic radiation that produces a light sensation in the human eye, i.e. it can be seen. It is radiation between 380 and 780 nm, i.e. only a tiny part of the known spectrum of electromagnetic radiation.

Luminous flux φ - unit lumen [lm]
Luminous flux indicates how much light the light source emits in total in all directions. It is the light output that is judged
in terms of the sensitivity of the human eye.

Light source power Ŋ - unit lumen per Watt [lm/W]
The specific luminous flux indicates the ratio of luminous flux to the power input of the source, i.e. how efficiently the supplied electrical power is converted into light.

Luminance I - candela unit [cd]
A light source generally emits its light flux in different directions with different strengths. The intensity of light emitted in one particular direction is referred to as luminous intensity. Luminance is therefore a measure of the luminous flux emitted at a spatial angle.

Illuminance E - unit lux [lx]
Illuminance indicates the ratio of the incident luminous flux to the illuminated
area. Illumination intensity of 1 lx corresponds to a luminous flux of 1 lm incident
evenly over an area of 1 m2.

Color Rendering Index Ra (CRI - color rendering index)
Color rendering fidelity CRI is a dimensionless unit that evaluates the fidelity of the color perception of an object illuminated by a particular light source against the fidelity of the color perception that would be produced by the sun. The CRI value can take values from 0 to 100.

Chromaticity temperature Tc - unit Kelvin [K] (CCT - correlated color temperature)
It characterises light by its temperature, which corresponds to the temperature of a blackbody emitting in the same colour spectrum. The lower the numerical value, the more red the colour of the light; the higher the value, the more blue the colour of the light.

The degree of protection against external mechanical impacts, the classification of mechanical resistance IK is determined by the European standard ČSN EN 62262.

The IK mechanical resistance classification determines the degree of protection that provides the device with protection against external mechanical impacts. The mechanical resistance designation consists of the letters IK and indicates its level on an eleven-step scale ('00' to '10').

The higher the numerical value of the IK parameter, the higher the mechanical resistance.

The enclosure of electrical equipment expresses the degree of protection against contact with dangerous parts and against the ingress of foreign solids, dust and water. The degree of protection is indicated by the letters IP (international protection) and is standardised according to EN 60529.
After the letters IP there is a characteristic double protection number, or an additional and supplementary letter that describes the test method.

If the luminaire is marked IP66/IP67/IP69, this means that it meets three separate protection tests.

ATEX Directive
Electrical equipment and apparatus intended for use in potentially explosive atmospheres that are subject to the requirements of the ATEX Directive. This Directive sets out the technical requirements for the assessment of the conformity of equipment and protective systems intended for use in potentially explosive atmospheres when they are placed on the market.

Installations are divided into appropriate groups and categories according to this Directive.

Equipment group I - Installations for underground mines with the presence of mine gas (methane) and/or combustible dust.

Equipment Group II - Installations for explosion hazardous areas outside underground mines with the presence of mine gas (methane) and/or combustible dust.

(a) Category 1 GD equipment
It includes installations designed to operate in accordance with the operating parameters specified by the manufacturer and to provide a very high level of protection. Installations in this category are intended for use in areas where explosive atmospheres created by gases, vapours, mists or mixtures of dust and air occur on a continuous, prolonged or frequent basis. Installations in this category must provide the required level of protection even in the event of exceptional equipment-related events.
ZONE 0/20 (Ga, Da)

(b) Equipment category 2 GD
It includes installations designed to operate in accordance with the operating parameters specified by the manufacturer and to provide a high level of protection. Installations in this category are intended for use in areas where explosive atmospheres may occasionally be created due to the presence of gases, vapours, mists or mixtures of dust and air.
The protection measures applicable to installations in this category ensure the required level of protection even in the event of frequent faults or equipment failures that must be taken into account on a regular basis.
ZONE 1/21 (Gb, Db)

(c) Equipment category 3 GD
It includes installations designed to operate in accordance with the operating parameters specified by the manufacturer and to provide a basic level of protection. Installations in this category are intended for use in areas where explosive atmospheres created by gases, vapours, mists or dusts are unlikely to occur and, if they do occur, are likely to occur only rarely and for short periods of time. Installations in this category provide the required level of safety during normal operation.
ZONE 2/22 (Gc, Dc)