OHST Practice Exam

What is the maximum allowable accumulation of flammable gases during the starting sequence of a gas-fired drying oven?

1. 0%

2. 5%

3. 15%

4. 25%

The correct answer is: 25%

The correct answer is 25% because safety standards for flammable gases often permit a maximum concentration of 25% of the lower explosive limit (LEL) during specific operations in controlled environments like a gas-fired drying oven. This threshold is established to minimize the risk of ignition while allowing for safe operational practices. In industrial settings, understanding the LEL is crucial because it indicates the lowest concentration of gas that can ignite in air. For many flammable gases, a concentration of 25% of the LEL is considered a safe upper limit for accumulation during start-up or other operations. This value strikes a balance between operational efficiency and safety, ensuring that there is adequate ventilation and monitoring to prevent hazardous conditions. Regulatory bodies and industry standards are in place that detail these limits, and adhering to them is important for the safety of personnel and equipment in industrial processes. Other options, like 0%, 5%, and 15%, do not reflect recognized safety thresholds for flammable gas accumulation. While lower concentrations would further reduce risk, they are often not practical or necessary for efficient operation, particularly in a controlled environment where safety measures are employed.