What is the maximum concentration of Carbon Dioxide that a person can be exposed to at the mine?

• A. 25000 ppm
• B. 5000 ppm
• C. 12500 ppm
• D. 30000 ppm

Answer: (C)

In mine air, keeping carbon dioxide below a set limit protects workers from asphyxiation and impaired judgment. In Queensland coal mining practice, the maximum permissible concentration of CO2 is 12,500 ppm. This level is chosen because it provides a safety margin: high enough to be achievable with practical ventilation, but low enough that CO2 displaces enough oxygen to cause symptoms or danger if it rises further. If CO2 approaches this limit, it signals that ventilation needs to be increased or the affected area isolated or evacuated.

The other numbers are either typical general workplace thresholds or are simply too high to offer adequate protection in a mining environment. Lower values like 5,000 ppm are common minimum health limits in some contexts, but the mine regulation uses 12,500 ppm as the ceiling for acceptable exposure. Higher values, such as 25,000 or 30,000 ppm, would pose serious, rapid risks to health and are not acceptable as limits.