VOC Online Monitoring System: Guardian of Industrial Exhaust Management and Safety

Volatile Organic Compounds (VOCs) are common pollutants in industrial production, widely present in painting, printing, pharmaceutical, chemical, coatings, adhesives, and electronics manufacturing industries. These compounds are highly volatile and reactive, directly participating in atmospheric photochemical reactions, forming ozone and secondary organic aerosols (SOA), worsening PM2.5 and ozone pollution, and posing various toxic, irritant, or even carcinogenic risks.

In recent years, China has strengthened VOC control. Policies such as the "Unorganized Emission Control Standard for VOCs" (GB 37822-2019) and "Comprehensive VOC Control Plans for Key Industries" require key sources to implement online monitoring and direct data transmission. Without effective monitoring, enterprises face environmental penalties, production restrictions, and potential safety incidents. The Nexisense SGA-900 series VOC online monitoring system, with high adaptability, reliability, and customizable features, has become the preferred solution for achieving compliant VOC emissions and process safety management.

VOC Emission Risks and Monitoring Necessity

VOCs include benzene series, halogenated hydrocarbons, ketones, esters, alcohols, and ethers, with industry-specific pollutants:

• Painting workshops: benzene, toluene, xylene, high TVOC concentrations

• Printing & packaging: ethyl acetate, isopropanol, ketone solvents

• Pharmaceutical & chemical: methanol, ethanol, chloroform, acetone

• Electronics manufacturing: isopropanol, n-butanol, PGMEA

Low concentrations can cause odor nuisance, while high concentrations directly threaten human health and production safety. Monitoring challenges include:

• Wide concentration range: from ppb (fence line) to thousands of ppm (stacks)

• Complex conditions: high temperature, high humidity, dust, corrosive gases

• Varied components: single sensors cannot cover all compounds

Traditional portable sampling or manual analysis cannot meet continuous, real-time, automatic monitoring requirements. Fixed online monitoring systems have become the mainstream technology for VOC control.

Nexisense SGA-900 Core Components and Working Principle

• High-temperature sampling probe (up to 800℃)

• High-temperature filter + efficient dust removal unit

• Condensation dehumidifier + desiccant

• Imported vacuum sampling pump + precision flowmeter

• High-performance PID or GC-FID analyzer

• Industrial control unit + data acquisition and transmission module

• Corrosion-resistant enclosure (IP65+)

  
  

Typical workflow:

1. High-temperature probe inserted into stack or hood to extract hot exhaust gas

2. Exhaust passes high-temperature filter to remove particles

3. Gas enters condensation and drying unit to remove moisture

4. Clean sample gas enters PID or GC chamber

5. Sensor detects TVOC or specific components, outputs real-time mg/m³ or ppm

6. Data transmitted via 4–20mA, RS485 Modbus RTU, or HJ212 protocol to control room/environmental platform

The system supports auto-calibration, fault self-diagnosis, and data retransmission to ensure reliable data integrity.

High-Temperature Probe and Pretreatment: Key for Complex Conditions

• Customizable probe length for various duct sizes

• Built-in high-temperature ceramic filter to prevent clogging

• Optional heating or cooling to avoid condensation or overheating

• Quick installation structure for easy maintenance

For high humidity and dusty environments, dedicated filtration and dehumidification components ensure clean, dry sample gas and prevent sensor contamination or drift.

Range Customization and Multi-Scenario Adaptability

• Painting workshops/unorganized emissions: 0–200 ppm

• Printing & adhesive production: 0–1000 ppm

• Stack organized emissions: 0–5000 ppm or higher

• Fence line sensitive points: 0–10 ppm or ppb-level

Supports single-component (benzene, toluene, TVOC) or multi-component monitoring to meet different processes and regulatory requirements.

System Integration and Linkage Control

• Seamless integration with PLC, DCS, or environmental platforms

• Real-time concentration display and historical trend curves

• Over-limit automatic alarms (sound, light, SMS)

• Linkage control: auto-start fans, stop painting pumps, open activated carbon valves when VOC exceeds limits

• Direct data transmission to environmental authorities, supporting daily/monthly report generation per HJ212 protocol

Installation, Commissioning, and Routine Maintenance

Installation suggestions:

• Sampling point on stack straight section or main hood outlet

• Probe insertion depth: 1/3–1/2 of duct radius

• Pretreatment cabinet on maintenance-friendly platform

• Ensure proper heating, cooling, and purge gas lines

Maintenance recommendations:

• Check filters and condensate weekly

• Zero/span calibration monthly using standard gas

• Clean probe and piping quarterly

• Replace PID lamp or GC column regularly (1–2 years)

  
  

FAQ

1. How to cover wide concentration ranges? Supports 0–10 ppm to 0–10000 ppm, custom range and alarms per process.

2. Why is high-temperature probe needed for hot flue gas? Standard tubes deform, release background VOC, or condense >300℃. SGA-900 probe can sample up to 800℃.

3. How to prevent sensor drift in humid/dusty conditions? Uses high-temp filter, auto backflush, dual condensation, desiccant; regular inspection extends life.

4. How to meet environmental data transmission requirements? Built-in HJ212 protocol, supports 4G/5G/Ethernet, breakpoint resume, auto daily/monthly reports.

5. Can it link with ventilation/solvent recovery systems? Yes, via 4–20mA, RS485, or digital signals for automatic control.

6. PID vs GC-FID? PID: fast response, wide range, suitable for TVOC/benzene-dominant painting/printing. GC-FID: high accuracy, strong component separation, suitable for precise chemical/pharma measurements.

7. Maintenance cycle for high-temp probe and pretreatment? Check filter monthly, clean probe/piping quarterly; common issues: filter blockage, heating failure.

8. How to optimize production using VOC data? Analyze VOC vs production load, spray amount, drying temperature to adjust ventilation and solvent usage, saving 10–30% solvents and reducing treatment cost.

Conclusion

VOCs control is a key battle in the fight for clean air. The Nexisense SGA-900 series, with extreme condition resistance, flexible range, high-precision analysis, and reliable linkage control, provides a complete solution from source monitoring to process optimization for painting, printing, chemical, and pharmaceutical industries. Deploying a professional VOC online monitoring system ensures compliant emissions, avoids penalties, and enables data-driven energy savings and green production.