What are VOCS?
Volatile organic compounds (VOCs) are a wide range of carbon based (organic) chemicals (compounds) found in various man-made and naturally occurring solids and liquids. They evaporate easily at ordinary room temperature which is why they are termed volatile.
Why measure VOCs?
Some VOCs are harmful to human health and can cause environmental damage. Exposure to high concentrations of VOCs can lead to throat irritation, headaches and damage to internal organs. Continuous low level exposure often causes long-term health effects. The severity of the health effect depends largely on the type of organic compound present as well as the exposure time.
Where do VOCs come from?
Typical indoor VOC sources include paint, cleaning supplies, furnishings, glues, permanent markers and printing equipment. Levels can be particularly high when there is limited ventilation.
Typical outdoor sources include emissions from the oil and gas industry, solvent usage and transportation. Athough biological VOC emissions tend to be larger overall, man made sources are a greater concern in urban areas.
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VOCs are commonly monitored as they are a key contributor in photochemical smog. Many are hazardous to human health, with several classified as carcinogenic. The key sources of VOCs are industrial processes (especially those involving solvents) vehicle emissions, evaporative loss from petrol storage and even natural sources like forest fires.
- Indoor air quality
- Personal exposure studies
- Health and safety
- Checking indoor air pollution “hotspots”
- Urban air monitoring networks
- National air monitoring networks
- Roadside air monitoring
- Industrial perimeter monitoring
- Environmental impact assessments
- Research and consultancy projects
- Short term hot spot monitoring
What VOC Sensor To Use
Aeroqual VOC Sensors
Aeroqual offers two types of VOC measurement sensors; Photoionization Detector (PID), and Gas Sensitive Semiconductor (GSS). Both sensor types are non-selective which means they can be used for measuring a wide variety of VOCs. To achieve this they have been calibrated against isobutylene that allows them to respond to a wide range of VOCs at varying degrees of sensitivity. Each type has a calibrated measurement range against a set of VOCs. PID type VOC sensors are more resilient and can detect a wider variety of VOCs.
Measuring targeted VOCs
Targeted VOC measurements are useful in controlled environments (e.g. labs, research) where the target compound is used and process control or health and safety risks are required. To measure a targeted VOC, a known correction factor is applied to calculate the relative value from isobutylene that is used for the sensor calibration. However, to avoid a cross interference no other VOCs should be present in the monitoring environment. For greater accuracy the sensor can be calibrated to the target VOC using a calibration gas of the target compound.
Measuring mixed VOCs
Mixed VOC measurement are commonly used to detect the presence of VOCs in uncontrolled environments (e.g. offices, outdoors) to determine air quality. In this scenario the measurement is used as a relative indicator of the presence and level of VOCs in the environment. Some VOCs will influence the reading more than others – known as cross-interference – the measurement is therefore only a reference indication to the air quality.