Model GN Type E Combustible Gas Indicator

The Model GN type E combustible gas indicator (fig. 6-35) has a scale of 0% to 100% LEL. The scale is color-coded red above the 60% mark to readily indicate dangerous gas concentrations. Use the following procedures to operate the combustible gas indicator:

1. Attach the necessary amount of sampling hose.

2. Open the hinged cover panel and turn the ON-OFF switch to ON.

3. Depress the VOLT TEST switch with your left hand and note the reading on the indicating meter. The meter pointer should point directly to the SET VOLTAGE mark on the meter scale. To adjust the voltage, lift the voltage adjustment knob, and rotate the knob until the meter pointer points to the SET VOLTAGE mark. If the meter pointer stays to the left of the mark after complete clockwise rotation of the knob, replace the batteries. Eight D-cell batteries (BA-30) are required.

4. Pump the aspirator bulb several times to clear any residual gas from the indicator. Make sure that you are in a gas-free atmosphere when clearing the indicator.

5. Lift the ZERO ADJUST KNOB and rotate the knob each direction. Make the meter pointer move up and down the scale several times. Then adjust the ZERO ADJUST KNOB until the meter pointer reads zero on the scale.

6. When you are ready to take a sample, insert the sampling hose into the space being checked. Squeeze the aspirator bulb three or four times for the indicator and three times for each 5 feet of sampling hose used.

The meter pointer will fluctuate while you squeeze the aspirator bulb. If there is a gas

Figure 6-35.-Model GN type E combustible gas indicator.

concentration present, the meter pointer will indicate the percentage. Clear the indicator in a clean atmosphere after each reading by squeezing the aspirator bulb until the meter pointer returns to zero on the scale. The indicator ON-OFF switch will return to the OFF positions when you shut the cover.