What Are Volatile Organic Compounds (VOCs)?

VOCs are any variety of organic, carbon-containing chemical compounds that release gaseous molecules from their liquid or solid form at room temperature. While many VOCs are naturally occurring and important to environmental interactions, a large number are emitted in manmade processes and are hazardous to human health if inhaled at certain concentrations. The EPA has determined that concentration of VOCs are much higher indoors compared to outdoors (up to 10 times higher), and it is estimated that 50 to 300 different VOCs may be detected in the air of homes, schools, offices, and commercial buildings at any given time. The adverse health effects caused by breathing in these chemicals can range from the temporary irritation of the eyes or throat, nausea, and headache, to long-term disease such as cancer or damage to liver, kidneys, or central nervous system.

VOCs in the home
Image courtesy of Prime Property Inspectors

How Does PID Technology Work?

To accurately measure the most common VOCs found in homes or offices to concentrations of parts per billion (ppb), E Instruments' indoor air quality monitors use Photo-Ionization Detection (PID) technology. Each PID sensor is equipped with a UV lamp which emits high energy protons onto a sample of ambient air drawn into the sensor chamber (see diagram below). When hit with this UV light, most VOC molecules, with the exception of low molecular weight VOCs, will break up into free electrons and positively charged ions, a process call ionization. This ionized gas is electrically charged and produces an electric current. The ion current is collected by the sensor, amplified and converted to a reading either in ppb or ug/m3. The greater the concentration of VOCs in the air sample, the greater the current that will be generated and detected by the PID sensor.

How PID technology works
Image courtesy of EQUIPCO Services
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