ENVIRONMENTAL MONITORING Volatile threat
John Clements, former managing director of monitoring equipment specialist company Signal Group, explains why monitoring is essential for VOC emissions reduction
I
n general, volatile organic compounds (VOCs) are harmful to both health and the environment, so management of the associated risks needs accurate and reliable monitoring. There are two main areas of concern: indoor
and outdoor VOCs, for which the definition of VOCs is different. Indoors, VOCs are organic chemical compounds
which evaporate under normal indoor atmospheric conditions of temperature and pressure. Some organic chemicals are harmful to the skin and can be absorbed, but volatility makes it possible for VOCs to be breathed in and cause a wide variety of negative health effects ranging from minor irritation to death. In the outdoor environment, the main concern
with VOCs is their role in the formation of ozone. At ground level, ozone is generated when VOCs react with sources of oxygen molecules, such as nitrogen oxides, and carbon monoxide in the atmosphere in the presence of sunlight. Ozone can be harmful to health, particularly in children, the elderly and people with cardiovascular problems. In the outdoor environment, VOCs are commonly
defined as any organic compounds which are emitted from non-natural processes and have photochemical ozone creation potential. This is generally interpreted as any organic compound released to the atmosphere from an operator’s plant or process, excluding releases of naturally produced VOCs from within the plant boundary and methane. The emissions of regulated processes with the
potential to release VOCs are issued with permits that include an emission limit for total organic carbon (TOC). The standard reference method for the measurement of TOC is with a flame ionisation detector (FID). In some cases, where there is a
potential for the emission of particularly toxic VOCs, the site permit may include a requirement for the monitoring of individual organic compounds.
WHAT IS A FID? A flame ionisation detector measures the concentration of ions produced when hydrocarbons in a sample are burned in a flame. Hydrogen or a hydrogen/helium mixture is used as the fuel for the flame which burns in hydrocarbon-free combustion air. An electric field is generated by a polarisation voltage between two electrodes and the ions generated by the combustion result in a charge which is directly proportional to the quantity of carbon atoms derived from organic compounds in the sample. There are a number of manufacturers developing
portable VOC detectors, most of which employ a photoionisation detector (PID). However, this technology is not suitable for TOC emissions monitoring because of the enormous variation in response factor between different VOCs.
TECHNOLOGY DEVELOPMENT As technology develops, Signal is also developing its analysers to find new levels of performance and features that make the instruments more reliable and easier to use. For example, the latest FIDs from Signal, the Series IV, build on their predecessors’ rugged reliability and repeatability with greater levels of sensitivity and now provide remote connectivity. With 3G, 4G, GPRS, Bluetooth, WiFi and satellite compatibility, each instrument is built with its own IP address and runs on Windows software. As a result, users are provided with simple and secure access to their analysers at any time, from anywhere, making the analysers ideal for
❱❱ The Series IV Solar Flame Ionisation Detector from Signal Group is available as a rack mounted or portable instrument
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There are
two main areas of concern, indoor and outdoor VOCs
March 2019 /// Testing & Test Houses /// 19 ’
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