PID VOC sensor in industrial applications

In the fields of industrial production such as petroleum, petrochemicals, chemicals, and pharmaceuticals, there are a large number of volatile organic compounds (VOCs). According to the definition by the US Environmental Protection Agency (EPA): All compounds with carbon are called organic compounds, and volatile organic compounds refer to volatile compounds with a boiling point of 50-260 and a saturated vapor pressure of more than 133.32Pa at room temperature. Its main components are hydrocarbons, oxygen hydrocarbons, halogenated hydrocarbons, nitrogen hydrocarbons, and sulfur hydrocarbons. The root cause of many dangerous hidden dangers in the industrial field is excessively harmful substances, and most of these dangerous and harmful substances are VOCs. The detection of VOCs plays a very important role in the production and transportation management of flammable and explosive materials, leakage of chemical materials, heat exchange fluids, industrial hygiene, indoor air quality, environmental protection, entry into confined spaces, and emergency accident detection. VOC components are very complex, and various gases are often mixed in industrial sites. It is impossible to detect each volatile organic gas like conventional electrochemical sensors. Therefore, a VOC detection instrument that can accurately measure the total amount of volatile organic compounds is needed.

PID sensor for VOC detection
PID sensor for VOC detection

Introduction and hazards of VOC

VOC is the abbreviation of Volatile Organic Compounds. It usually refers to organic compounds that are easily volatile at room temperature. The more common ones are benzene, toluene, xylene, ethylbenzene, styrene, formaldehyde, TVOC (alkanes with 6-16 carbons), ketones, etc. These compounds are volatile and lipophilic and are widely used in industrial fields such as footwear, toys, paints and inks, adhesives, cosmetics, interior and automotive decoration materials. VOC has a huge impact on human health, which can damage the liver, kidneys, brain, and nervous system, cause serious consequences such as memory loss, and may even cause cancer.

Industrial PID TVOC Sensor FS4PIDTVOC (5)
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PID sensor for VOC detection

1. What is PID

Photoionization detectors (PHOTO IONIZATION DETECTORS) can measure VOC (volatile organic compounds) and some toxic gases in the range of (50ppb-6000ppm). Many hazardous raw materials contain VOC. Due to its high sensitivity to VOC, PID has become an indispensable practical tool for early warning of hazardous substances and leakage monitoring. At present, the service life of the bulb has been greatly extended by upgrading the bulb and internal IC.

The photoionization alarm can detect VOC and other toxic gases from 10ppb (parts billion) to 10000ppm (parts per million). PID is a highly sensitive and widely applicable detector. PID can be regarded as a “low concentration LEL detector”. If toxic gases and vapors are regarded as a big river, even if you swim into the river, the LEL detector may not respond, but PID will tell you when you just get your feet wet.

2. Advantages of PID sensors

  1. High precision

High-precision photoionization sensors can detect organic gases at the ppb level (parts per billion), and general photoionization gas sensors can detect organic gases at the ppm level (parts per million), with an accuracy exceeding that of most common sensors such as infrared sensors;

  1. Non-destructive to the detected gas

Photoionization sensors ionize the gas after inhaling it, and the ions formed by the gas molecules re-form the original gas molecules after discharge, which is non-destructive to the original gas molecules.

  1. Fast response speed and long life

Except for the period of preheating of the gas detection system after startup, under normal working conditions, the photoionization gas sensor can respond almost in real-time and can be tested continuously. When detecting dangerous gases, it is of great significance to protect the health of the detection personnel. Generally, the life of a UV lamp is thousands of hours, and the photoionization sensor can work normally during this period and has a long service life.

  1. Wide range of applications

Photoionization sensors can detect most organic and some inorganic gases and can be widely used in chemical, transportation, military, aerospace, and other fields. Since photoionization gas sensors are particularly sensitive to changes in the concentration of the detected object, they play an important role in initial personal protection confirmation, leakage area confirmation, and pollution removal.


Working principle of PID VOC detector

PID uses an ultraviolet (UV) light source to ionize organic molecules into positive and negative ions (ionization) that can be detected by the detector. The detector captures the positive and negative charges of the ionized gas and converts them into current signals to measure the gas concentration. When the gas to be measured absorbs high-energy ultraviolet light, the gas molecules are excited by the ultraviolet light and temporarily lose electrons to become positively charged ions. After the gas ions are detected on the electrodes of the detector, they will quickly combine with electrons to reconstitute the original gas and steam molecules. PID is a non-destructive detector that does not change the gas molecules to be measured. The gas detected by PID can still be collected for further measurement.