As per Indian Standard (IS 287: 1993), India is divided into how many zones based on its relative humidity for air seasoning of timber?
Why Zoning for Air Seasoning?
Air seasoning is the process of drying timber by exposing it to the natural air. The rate and effectiveness of this process depend heavily on the climate, particularly the relative humidity. A region with high humidity will dry timber much slower than an arid region. To standardize practices and recommendations for seasoning across a large and climatically diverse country like India, the Bureau of Indian Standards (BIS) divided the country into zones based on climate.
📝 Detailed Analysis of the Options
(a) Two, (b) Five, and (d) Three
These numbers are incorrect according to the specified standard. IS 287: 1993 explicitly defines a specific number of zones to cover the diverse climatic conditions across India for the purpose of timber seasoning.
(c) Four
This is the correct answer. According to Indian Standard IS 287: 1993 (Code of practice for recommendation for maximum permissible moisture content for timber), India has been divided into four zones for the air seasoning of timber. This classification is based on the average annual relative humidity, which directly influences how timber dries in different parts of the country.
📊 IS 287: 1993 Timber Seasoning Zones of India
| Zone | Average Annual Relative Humidity |
|---|---|
| Zone I | Less than 40% |
| Zone II | 40% – 50% |
| Zone III | 50% – 67% |
| Zone IV | More than 67% |
💡 Study Tips
- Remember the Standard: Associate IS 287 with timber moisture content and seasoning zones.
- The Magic Number is 4: For the purpose of this standard, the number of zones for timber seasoning in India is four.
- Humidity is Key: Understand that the basis for this zoning is relative humidity, as it's the most critical factor in the air-drying process.