Tianhong TH-318 Ambient Air TVOC Online Monitoring System

Overview

The Tianhong TH-318 Ambient Air TVOC Online Monitoring System is a field-deployable, real-time total volatile organic compounds (TVOC) analyzer engineered for continuous ambient air monitoring. It employs photoionization detection (PID) technology with a high-stability 10.6 eV ultraviolet lamp—optimized for ionizing a broad spectrum of VOCs including aromatics, alkenes, ketones, esters, and chlorinated hydrocarbons while exhibiting minimal response to methane and other saturated aliphatics. Unlike flame ionization detectors (FID) or metal oxide semiconductor (MOS) sensors, the TH-318 delivers selective, interference-resistant quantification in the low-ppb to mid-ppm range without requiring carrier gas or high-temperature operation. Its compact, vehicle-integrated architecture supports mobile monitoring applications—including emission mapping, hotspot identification, and boundary fence-line surveillance—making it suitable for regulatory compliance verification, industrial site assessment, and community exposure studies under ISO 16000-29 and EPA Method TO-15/TO-17 frameworks.

Key Features

• Integrated sampling pump with flow-controlled aspiration (0.5–1.2 L/min), ensuring consistent sample draw across variable ambient pressure and temperature conditions
• 10.6 eV PID sensor with <10 s response time (t₉₀) and <±3% full-scale repeatability over 30-day calibration interval
• Onboard touch-screen calibration interface supporting multi-point (up to 5 points) span and zero adjustment using certified isobutylene standard gas delivered via integrated dynamic dilution generator
• Real-time environmental compensation for temperature (−20°C to +50°C), barometric pressure (60–110 kPa), and relative humidity (10–90% RH non-condensing)
• RS-232/RS-485 serial output with Modbus RTU protocol; compatible with GIS-enabled data loggers and mobile mapping platforms for second-by-second spatial concentration visualization
• Industrial-grade 4.3-inch TFT LCD touchscreen (800×480 resolution) with sunlight-readable brightness (≥1,000 cd/m²) and glove-compatible capacitive touch layer
• Rechargeable Li-ion battery pack (14.8 V / 12 Ah) enabling ≥24 h continuous operation at 25°C; supports hot-swap battery module replacement during field deployment

Sample Compatibility & Compliance

The TH-318 is validated for direct analysis of unfiltered ambient air matrices without preconcentration or thermal desorption. It meets performance criteria outlined in HJ 644–2013 (China’s Standard for Determination of Volatile Organic Compounds in Ambient Air by Sorbent Tube Sampling and Thermal Desorption–Gas Chromatography–Mass Spectrometry) for screening-level TVOC assessment. While not a definitive speciation tool, its PID response factor library (based on isobutylene equivalence) enables traceable semi-quantitative reporting aligned with EU Directive 2008/50/EC Annex IX requirements for indicative measurement methods. The system complies with IEC 61000-6-2 (EMC immunity) and IEC 61000-6-3 (EMC emissions), and its enclosure meets IP54 ingress protection rating for outdoor vehicular mounting.

Software & Data Management

The embedded firmware supports local data storage (≥30 days at 1 Hz sampling) and configurable export via USB mass storage or SD card. All calibration events, sensor diagnostics, and environmental metadata are automatically timestamped and logged with audit-trail integrity. Optional cloud connectivity (via optional 4G LTE module) enables remote configuration, firmware updates, and secure TLS 1.2–encrypted data transmission to centralized environmental information systems (EIS). Data files conform to netCDF-4 format with CF-1.8 metadata conventions, facilitating interoperability with EPA AQS, EEA AirBase, and national air quality management platforms. Full GLP-compliant audit logs—including user login history, parameter modification timestamps, and sensor health flags—are retained for regulatory review.

Applications

• Mobile monitoring campaigns aboard electric-powered air quality survey vehicles for high-resolution TVOC mapping along urban corridors, industrial perimeters, and transportation corridors
• Supplemental screening at fixed-site air quality monitoring stations where rapid VOC trend detection complements GC-MS-based reference measurements
• Community-level exposure assessment in residential neighborhoods adjacent to petrochemical facilities, printing plants, or coating operations
• Pre-screening and anomaly localization prior to targeted canister (SUMMA®-can) sampling for subsequent laboratory analysis using PAMS-compliant instrumentation (e.g., Tianhong TH-300B VOC Speciation System)
• Short-term compliance verification during construction activities, solvent-based painting operations, or tank truck loading/unloading events

FAQ

What VOC compounds does the TH-318 detect?
The 10.6 eV PID detects most VOCs with ionization energies below 10.6 eV—including benzene, toluene, xylene, styrene, acetone, ethanol, and formaldehyde—but exhibits negligible response to methane, ethane, CO, CO₂, and NOₓ.
Can the TH-318 be used for regulatory reporting?
It serves as a screening and investigative tool per HJ 644–2013 and ISO 16000-29; final compliance determinations require confirmatory analysis using accredited GC-MS or GC-FID methods.
Is external power required during vehicle-mounted operation?
No—the system operates natively from its internal Li-ion battery or accepts 12–24 V DC vehicle power input with automatic switchover and surge protection.
How is calibration traceability maintained?
Calibration uses NIST-traceable isobutylene standard gas; all calibration parameters, dates, and operator IDs are digitally recorded with cryptographic hashing for audit integrity.
Does the TH-318 support integration with third-party GIS or SCADA systems?
Yes—Modbus RTU over RS-485 enables seamless integration with industrial automation platforms, municipal environmental dashboards, and open-source mapping tools such as QGIS and Leaflet.