What is meant by the term 'controlled ventilation'?

• A. Ventilation current of an average velocity of at least 0.3 m/s measured across the cross sectional area of the working place.
• B. Ventilation that operates only during daytime.
• C. Ventilation that uses only natural drafts.
• D. Ventilation based on ambient humidity levels.

Answer: (A)

Controlled ventilation means deliberately engineered airflow that is measured and maintained to achieve a specific average air velocity across the cross-section of the working area. This ensures the air moves consistently enough to dilute and remove heat, dust, and hazardous gases throughout the space, not just in a single spot. The defining criterion used here is an average velocity of at least 0.3 m/s across the cross section, which provides a clear, practical standard for adequate ventilation in mining settings. This emphasis on a measured, uniform air flow is what sets it apart from other ideas. Ventilation that operates only during daytime won’t guarantee continuous, uniform air flow. Relying on natural drafts means the flow is unpredictable and uncontrolled. Basing ventilation on ambient humidity doesn’t establish a controlled, directed air movement. So, the statement about maintaining an average velocity of at least 0.3 m/s across the cross-sectional area best defines controlled ventilation.