Annexure 2.3 EHS Guidelines
Rev 76, 202517
Guidelines for Lighting lux level survey
While general requirements for lighting system design & other requirements for light fixture
installation have been specified in Annexure 2.4 of ITC EHS guidelines. This guideline details out the
steps which needs to be followed for conducting a Lighting lux level survey:
A. Pre-requisite conditions:
1. Measurement of illuminance should be done after dark i.e., 60 min after sunset.
2. Lamps must be switched ON at least 30 min before the measurement survey.
3. Define the measurement height i.e. 0.8-1 m from the ground or floor level.
4. Stray light from windows or adjacent room should be minimised by use of curtains etc.
5. All the lighting in the area which would normally illuminate the area should be operating at
the time of measurement. Dimmer control etc., should be bypassed for the measurement tests.
6. Care must be taken so that the shadow does not fall on the photo cell of the lux meter. Also,
lux meter should not be placed just below the luminaire.
7. Calibrated Lux meters corrected for errors should be used for measurement of illuminance.
8. Accuracy of this lux meter should be 5% and its range should be upto 10000 lux.
9. Divide the area into equal sized squares as per the no. of points calculated from the Room
Index value.
10. Take the lux meter readings on each of these points and calculate the average illuminance
value. (Eav).
11. Calculate the installed load efficacy and load efficacy ratio to get final assessment as per the
procedure mentioned below.
12. For specific areas where spot illumination etc. is provided, the lux level should be checked by
placing the lux meter in the spot area, verified against the designed lux level & corrected if
found inadequate.
B. Calculation:
Lighting lux level surveys can be used to verify the performance of a lighting installation and improve
the efficiency of lighting in the building space. It is desirable to carry out lighting survey at new
installations during commissioning phase. For old installations, lighting survey should be carried out
once a year.
On site illuminance measurements are the core of any lighting survey and the illuminance can be
measured by a portable instrument called a lightmeter or luxmeter. A luxmeter indicates the
illuminance at the point of measurement only, not the average in the space. To find the average
illuminance in an area at the time, it is necessary to divide the area into a number of equal areas which
should be as nearly square as possible. The illuminance at each point is then measured, and the results
averaged. The minimum number of equal areas required for accuracy can be determined by first
working out the room index.
Room Index (k) = Length X Width
Hm X (Length + Width)
Where Hm is height of luminaries above the plane of measurement. Length and Width are
particular room’s length and width.
The minimum no. of points for measuring illuminance is taken as:
1
Rev 76, 202517
Guidelines for Lighting lux level survey
While general requirements for lighting system design & other requirements for light fixture
installation have been specified in Annexure 2.4 of ITC EHS guidelines. This guideline details out the
steps which needs to be followed for conducting a Lighting lux level survey:
A. Pre-requisite conditions:
1. Measurement of illuminance should be done after dark i.e., 60 min after sunset.
2. Lamps must be switched ON at least 30 min before the measurement survey.
3. Define the measurement height i.e. 0.8-1 m from the ground or floor level.
4. Stray light from windows or adjacent room should be minimised by use of curtains etc.
5. All the lighting in the area which would normally illuminate the area should be operating at
the time of measurement. Dimmer control etc., should be bypassed for the measurement tests.
6. Care must be taken so that the shadow does not fall on the photo cell of the lux meter. Also,
lux meter should not be placed just below the luminaire.
7. Calibrated Lux meters corrected for errors should be used for measurement of illuminance.
8. Accuracy of this lux meter should be 5% and its range should be upto 10000 lux.
9. Divide the area into equal sized squares as per the no. of points calculated from the Room
Index value.
10. Take the lux meter readings on each of these points and calculate the average illuminance
value. (Eav).
11. Calculate the installed load efficacy and load efficacy ratio to get final assessment as per the
procedure mentioned below.
12. For specific areas where spot illumination etc. is provided, the lux level should be checked by
placing the lux meter in the spot area, verified against the designed lux level & corrected if
found inadequate.
B. Calculation:
Lighting lux level surveys can be used to verify the performance of a lighting installation and improve
the efficiency of lighting in the building space. It is desirable to carry out lighting survey at new
installations during commissioning phase. For old installations, lighting survey should be carried out
once a year.
On site illuminance measurements are the core of any lighting survey and the illuminance can be
measured by a portable instrument called a lightmeter or luxmeter. A luxmeter indicates the
illuminance at the point of measurement only, not the average in the space. To find the average
illuminance in an area at the time, it is necessary to divide the area into a number of equal areas which
should be as nearly square as possible. The illuminance at each point is then measured, and the results
averaged. The minimum number of equal areas required for accuracy can be determined by first
working out the room index.
Room Index (k) = Length X Width
Hm X (Length + Width)
Where Hm is height of luminaries above the plane of measurement. Length and Width are
particular room’s length and width.
The minimum no. of points for measuring illuminance is taken as:
1
