BTEX and Benzene Measurement: Ambient Air Analyzers
GC-PID and GC-FID analyzers for measuring benzene, toluene, ethylbenzene, xylene (BTEX) and other VOCs in ambient air; continuous monitoring stations.
Measurement methods: Flame Ionization (FID), Gas Chromatography
What are BTEX and benzene, and why are they measured?
BTEX is the collective name for benzene, toluene, ethylbenzene and xylene. Among these compounds, which enter the air through the evaporation of petroleum products, solvents and vehicle fuels, benzene is the most closely monitored for human health. The main sources are refineries, petrochemical plants, storage and filling terminals, odor-affected areas and heavy traffic. Toluene and xylenes are precursors that contribute to ozone formation. BTEX is therefore tracked continuously or semi-continuously at air quality monitoring stations and in measurements around plants.
Where is BTEX measured?
- Around refineries and petrochemical plants: At the fence line and at neighboring residential points.
- Air quality stations: In urban and industrial background monitoring.
- Storage and filling areas: For tracking fugitive emissions.
Methods for measuring BTEX
Because BTEX components are chemically very similar, a total VOC measurement is not enough; gas chromatography is used so that each component can be known separately. An ambient air sample is collected periodically in a pre-concentration unit, separated on a column and measured component by component with a PID (photoionization) or FID detector. Depending on the application, 1,3-butadiene, vinyl chloride, ethylene oxide and mercaptans can also be measured in the same way, in addition to benzene. This arrangement is an automatically operating ambient air gas chromatograph, which updates its results at each cycle interval.
Choosing a BTEX analyzer
- List of components to be monitored and required detection level
- Supply of carrier and calibration gas; gas infrastructure with a nitrogen generator
- Standards requirement: compliance with the relevant EN method for benzene measurement in ambient air
- Calibration frequency and consumables
BTEX measurement with Tetra
Tetra supplies the Synspec GC955 BTEX/VOC gas chromatograph and Synspec Alpha FID/PID benzene analyzers in Türkiye. Station cabinet integration, nitrogen generator and gas station, commissioning, calibration and annual maintenance services are provided by Tetra.
Frequently asked questions
What unit is benzene measured in, in ambient air?
Benzene and other BTEX components in ambient air are generally expressed in µg/m³ or ppb. At 20 °C and 1013 hPa, 1 ppb of benzene corresponds to approximately 3.25 µg/m³. Because air quality assessment for benzene is based on annual average values, long-term and uninterrupted data is important.
Which standard applies to ambient air benzene measurement?
In Europe, the reference method for measuring benzene in ambient air is defined in the EN 14662 standard series; some parts of the series cover in-situ measurement by automated gas chromatography. It is advisable to check that an analyzer to be used at a continuous monitoring station complies with this standard and has type approval. Passive samplers (diffusion tubes) can be used as a complement for screening and long-term averages.
What are the measurement cycle and calibration of a BTEX gas chromatograph?
Automated ambient air GCs collect the sample in a pre-concentration unit over a set period, then separate and measure it; the result is updated at the end of each cycle, and the cycle time is typically on the order of minutes. Calibration is performed with certified gas mixtures containing known concentrations of BTEX, and component retention times are also checked for drift. The interval is set according to the instrument manual and the station's quality assurance plan.
What is the difference between a total VOC analyzer and a BTEX GC?
Total VOC analyzers give a total signal for all organic compounds and do not distinguish which component is being measured. This is not sufficient for a component such as benzene, which is assessed separately for health; a GC determines each component individually. This is why chromatographic methods are used for benzene monitoring aimed at legislation and health assessment.
Products measuring this parameter
Let's choose the right product together
Tell us about your application; we will recommend the right model and configuration for the measuring point, process conditions and regulations.