TVOC MANUAL
Ion Science Ltd
Page 6 of 32
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Introduction to TVOC
TVOC is a fixed continuous monitor for the detection and measurement of total volatile organic compounds,
which can be dangerous from both a poisoning and explosive perspective. Total VOC’s are detected using
PID (Photoionisation Detection) technology).
TVOC has a number of user selectable features which define its operation and will be application dependent.
The user can define the detection ranges or 0.01 - 10ppm, 0.1 – 100 ppm or 1 – 1,000 ppm (Default);
detection units, either ppm or mg/m
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; and the duty cycle time i.e. the frequency that the instrument takes a
measurement. Duty cycles are explained in more detail in section 4, TVOC set up, and section 6 Operation.
IMPORTANT: if the 10ppm range is selected the TVOC will require a calibration using 10ppm Isobutylene
before use.
The default settings of TVOC are:
Detection range
–
0.1 – 1000 ppm
Units
-
ppm
Duty cycle
-
5 seconds ON / 55 seconds OFF
TVOC gives a continuous 4 – 20 mA output which can be integrated into a DCS control system to give an
indication of VOC levels in the operating environment.
In addition to the 4 – 20 mA output TVOC has an LCD display showing gas concentration and 4 colour LED’s.
LED functions are as follows:
Green
- is an indicator of TVOC’s working status
Red
- is the fault indicator
Yellow x 2
- are calibration status indicators
Please see section 7 Calibration for more information on LED status.
For installation requirements please refer to sections 5 and 10 of this manual. For Intrinsically Safe (IS)
installations please also refer to the TVOC ATEX certificate for further details. Before attempting an
installation, please fully read and understand this user manual.
TVOC does require regular calibration onsite please see section 7 Calibration for information. TVOC
calibration mode is accessed via a magnetic read switch system.
The TVOC intrinsic safety rating permits its deployment in all hazardous areas of the quoted (or less
demanding) rating. That is, in areas where explosive gases (of Group IIA, IIB and IIC) are intermittently
present (Zone 1) within an ambient temperature range of -20
°
C and +60
°
C.
