ageing of the lamps

type of work carried out at the premises

lamp cleaning schedule

all of the above

size of the room

space height ratio of the lamps

colour of walls/ceiling

all of the above

increasing the mounting height of the lamp

using diffusers

using reflectors to cut-off the light at certain angle

all of the above

avoid glare

provide better illumination

protect the lamp

all of the above

depreciation in the capital cost of the installation

effects of dust, dirt and types of lamps used

effects of dust, dirt and fall in light-output of the lamp during its life

condition of the room and the type of lamp used