“eGC” Quick Guide Rev. 2
PURPOSE
This guide provides basic set-up and operating instructions for the ENMET “eGC” trace VOC
monitoring system.
GENERAL INFORMATION
The “eGC” is designed to automatically perform repetitive measurements of trace level (i.e., ppbv)
concentrations of benzene and other VOCs in ambient air.The VOC analyzer is based on a
miniaturized, temperature-controlled gas chromatograph. The basic eGC also contains a data-
logger connected to a GPS module that provides accurate location and time information along
with archived measurement data. Measurement data are automatically transmitted via an on-
board cellular data modem to ENMET’s internet-based web server where the data can be viewed,
archived and retrieved. The eGC performs one measurement every 10 minutes.
The eGC external enclosure protects the instrument from the environment. A fan inside the
enclosure draws in a large volume of ambient air to cool the device and to provide a
representative ambient air sample to the inlet of the analyzer. The mini-GC “engine” analyzer is
housed in a separate internal enclosure that is temperature controlled using a thermoelectric
cooler/heater (TEC). This arrangement allows accurate, reproducible measurements to be made
regardless of ambient temperature fluctuations.
Ambient air samples are collected at a flow rate of approximately 250 sccm for a period of 45
seconds and then injected from a thermally desorbed sample collector into a gas chromatograph
for analysis. The resulting chromatogram and associated measurement data reports are then
transmitted to the web-server.
The eGC can be configured for either 12VDC or 120VAC power. The low power consumption of
the eGC (< 60 Watts) makes solar-powered operation an attractive option.
The performance of the eGC can be enhanced by a variety of optional accessories, including:
• A sun-shade to limit exposure to direct sunlight.
• A wind speed/direction sensor
• A solar panel & battery power supply
• An elevated “Sample Inlet Snorkel” for unobstructed, 360° sampling
• A “Calibration Box” to supply scrubbed air and calibration gas to the eGC
• A “Continuous Sampler” accessory to allow ambient air samples to be collected 100%
of the time, without interruption
Regular calibration of the eGC is accomplished using compressed calibration gas supplied either
from an external, certified calibration gas cylinder (e.g., benzene @ 10 ppb) or, from the
“Calibration Box” accessory. The system has a built in flow meter to permit easy field adjustment
of the calibration gas flow (i.e., 400 sccm). Multiple daily calibrations (e.g., 6 hour intervals) are
recommended for highest accuracy.
UNPACKING AND INITIAL SET-UP
