A combustible gas instrument (CGI) indicates 30% of the LEL for hexane. With an LEL of 1.1 and a conversion factor of 0.8, what are the true concentrations?

The correct choice is based on analyzing how to interpret the readings from a combustible gas instrument (CGI) regarding hexane, considering its lower explosive limit (LEL) and the given conversion factor.

To find the true concentration of hexane when the CGI shows 30% of the LEL, you first must determine the absolute concentration in terms of LEL. The LEL for hexane is specified as 1.1%, and since 30% of this limit is being indicated by the CGI, the first step involves calculating 30% of the LEL.

Calculating this gives:

0.3 (or 30%) multiplied by the LEL of 1.1% results in an initial concentration of 0.33%.

Next, to convert this percentage into parts per million (ppm), you utilize the conversion factor provided in the question. The conversion from percent concentration to ppm can generally be calculated by the formula:

[ \text{ppm} = \text{percentage} \times 10,000 ]

Thus,

0.33% multiplied by 10,000 equals 3300 ppm.

However, since there's a specific conversion factor of 0.8 applicable here, we must adjust this value:

330