Why are chimneys of factories kept high?

Explanation

### Step-by-Step Solution:

1. **Understanding the Purpose of Chimneys**:
- Chimneys in factories are designed to expel polluted air produced during industrial processes. The primary goal is to ensure that the air released into the environment is as clean as possible.

2. **Role of Convection**:
- The process of convection plays a crucial role in the functioning of chimneys. Convection is the transfer of heat through the movement of fluids (in this case, air). When air is heated, it becomes less dense and rises.

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