PID Sensors for VOC Gas Detection

Volatile Organic Compounds (VOCs) are carbon-based chemicals that evaporate at room temperature. The term “VOC” may refer to a single compound or collectively to all such compounds.

Scientific Definition Variations

Different organizations define VOCs based on specific regulatory needs:

• ASTM d3960-98: Organic compounds participating in atmospheric photochemical reactions.

• US EPA: Carbon compounds in photochemical reactions (excluding CO, CO₂, carbonates, etc.).

• WHO (1989): TVOCs = VOCs with melting point < room temp & boiling point 50-260°C.

• China GB/T 18883-2002: TVOCs = Compounds eluting between n-hexane and n-hexadecane on non-polar columns.

▲ Key Insight: These variations exist because VOCs’ environmental impact depends on their photochemical reactivity – a key driver of ground-level ozone formation.

Beyond VOCs: The Organic Spectrum

Atmospheric organics exist in three states:

1. VOCs (Gaseous at room temp)

   • Examples: Formaldehyde, benzene

2. SVOCs (Semi-volatile)

   • Transition between gas/particulate phases with temperature changes

   • Examples: Pesticides, flame retardants

3. NVOCs (Non-volatile)

   • Bound to particulate matter (PM2.5/PM10)

   • Examples: Heavy hydrocarbon residues

Environmental Impact:

All three classes contribute to:

• Photochemical smog (VOCs + NOx + sunlight → Ozone)

• Indoor air pollution (WHO attributes 4.3M annual deaths to household air contaminants)

• Climate feedback loops (e.g., terpenes from forests form cloud nuclei)

Alphasense PID Sensors: Precision VOC Detection

How PIDs Work:

Photoionization Detectors (PIDs) use ultraviolet light to ionize VOCs. When molecules absorb UV photons, they release electrons, generating measurable current proportional to concentration (ppb-ppm range).

ISweek now supplies PID sensors from Alphasense which can detect VOC gas. The features of this product are as follows:

Photoionization Gas Sensor (PID Sensor) – PID-A1

1. Large measurement range of 0~6000ppm
2. Minimum detectable concentration of VOC is 50ppb
3. The light bulb is of 10.6eV
4. Long service life of light bulb up to 5000 hours
5. Be able to measure most VOC gases
6. Linear output

Photoionization Gas Sensor (PID Sensor) – PID-AH

1. High resolution of 0~50ppm
2. Minimum detectable concentration of VOC is 1ppb
3. The light bulb is of 10.6eV
4. Long service life of light bulb up to 5000 hours
5. Be able to measure most VOC gases
6. Linear output