The illumination level required as per **ISI (Indian Standards Institution) standards** for various working planes in residential buildings is typically measured in **lux** (a unit of illuminance). Here are the recommended values:
1. **Kitchen Sink**: 150–300 lux
- This is a task-oriented area requiring good lighting for washing and food preparation.
2. **Staircase**: 100–150 lux
- Sufficient lighting is required for safety while using the stairs, but not as bright as task-oriented spaces.
3. **Dining Room**: 100–150 lux
- General ambient lighting for a comfortable dining environment is needed.
4. **Study Room**: 300–500 lux
- Higher illumination is necessary for reading and writing tasks.
These values help in providing a comfortable, functional, and safe lighting environment as per ISI standards.