If a coal mine section has a methane emission rate of 200 cubic feet per minute and the methane concentration is 0.2%, what is the required airflow if the threshold limit value of methane is 1.0%?

To determine the required airflow in a coal mine section with methane emissions, we must ensure that the concentration of methane remains below the threshold limit value (TLV) of 1.0%. The existing conditions include a methane emission rate of 200 cubic feet per minute (cfm) and a methane concentration of 0.2%.

First, we must calculate the total amount of methane that will be present in the mine atmosphere if the airflow is insufficient to dilute it. The concentration of 0.2% means that out of 100 parts of air, 0.2 parts are methane.

To calculate the required airflow to maintain a safe level of methane, we use the formula:

Required airflow = Emission rate / Safe concentration level

In this case, the safe concentration level is the threshold limit value of 1.0%. The existing methane emission rate is 200 cfm, so we set it up like this:

Required airflow = 200 cfm / (1.0% - 0.2%)

= 200 cfm / 0.8%

= 200 cfm / 0.008 (which is the decimal equivalent of 0.8%)

= 25,000 c