Exam Question

### (a) Reasons for Oxygen Deficiency in Shipboard Spaces
An atmosphere is considered oxygen-deficient when the oxygen concentration falls below 20.9% by volume (safe working level as per regulations, with alarms often set at 19.5%). Oxygen deficiency can occur due to two primary mechanisms: **consumption** and **displacement**.
Based on the provided context and established maritime safety principles, the reasons are as follows:
1. **Oxidation (Corrosion):** The process of rusting is the chemical reaction of iron (steel) with oxygen. In enclosed, damp spaces like ballast tanks, chain lockers, and cofferdams, this process can consume a significant amount of oxygen from the trapped atmosphere over time, leading to a dangerously deficient environment.