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Lighting schemes: local, general, emergency

Short answer

Lighting schemes are classified by distribution (direct, semi-direct, etc.) and coverage (general, local, emergency). General lighting provides uniform illumination over the whole floor. Local lighting concentrates high illuminance on small work areas with adjustable lamps. Emergency lighting automatically activates on power loss to light escape routes and critical areas.

State various types of lighting schemes. Explain local lighting, general lighting and emergency lighting used in an industry.

Types of lighting schemes

By light distribution: direct, semi-direct, general diffusing, semi-indirect and indirect lighting (decided by the fraction of light thrown downward, from 90–100 % for direct to 0–10 % for indirect).

By coverage of the area: general lighting, local (localised) lighting, general plus local lighting, localised general lighting and emergency lighting.

General lighting

General lighting provides a uniform level of illumination over the whole floor area, irrespective of the position of work. Luminaires of the same type are installed in a regular grid at a spacing within the allowed spacing-to-height ratio, usually with direct or semi-direct distribution.

  • Gives good uniformity (minimum/average ≥ 0.7) and allows machines to be moved freely.
  • Typical levels: 150–300 lux in workshops, stores and assembly areas.
  • Disadvantage: lighting the whole area to the level needed for fine work wastes energy.

Local lighting

Local lighting gives high illumination on a small working area, using lamps fixed on or near the machine (adjustable arm lamps, bench lights, machine lamps).

  • Gives 500–2000 lux where fine work, inspection or measurement is done.
  • Can be aimed to show surface texture and reduce shadows from the worker's body.
  • Must be used with some general lighting to avoid sharp contrast and eye fatigue; local lamps should be shielded to prevent glare and be low-voltage (24/48 V) in hazardous places.

Emergency lighting

Emergency lighting operates automatically when the normal supply fails, so that people can leave safely and dangerous processes can be shut down.

  • Escape lighting: lights exits, corridors, stairs and exit signs (about 1 lux minimum on escape routes).
  • Standby lighting: keeps essential work going (control rooms, hospitals, critical processes).
  • Sources: self-contained battery luminaires, central battery systems, UPS or DG sets with automatic changeover; batteries are usually rated for 1–3 hours.
  • Must be tested regularly.
Normal supply ──┬── General & local lights
                │
            [Charger]──[Battery]──┐
                │                 │
           (supply fails) → [Changeover] → Emergency lights

✓ Answer checked by Claude Opus 5.5 (high effort)

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