Tennessee Wastewater Operator Practice Exam

What substance is commonly added to reduce the risk of fire or explosion in enclosed spaces where biogas could accumulate?

1. Oxygen

2. Nitrogen

3. Carbon dioxide

4. Helium

The correct answer is: Nitrogen

Adding nitrogen to environments where biogas could accumulate effectively reduces the risk of fire or explosion. Nitrogen is an inert gas, meaning it does not support combustion. By displacing oxygen in the enclosed space, nitrogen reduces the availability of O2 that is necessary for fire or explosion to occur. In an atmosphere rich in biogas, which primarily consists of methane and carbon dioxide, the presence of oxygen poses a significant risk of flammability. Controlling the atmosphere by increasing the nitrogen concentration helps to mitigate this hazard substantially. Oxygen, on the other hand, would increase the risk of fire; carbon dioxide, while often used for extinguishing fires, does not serve the same purpose as nitrogen in preventing fire hazards when dealing with biogas; and helium, while another inert gas, is not typically used in this application.