Tianhong TH-680 Passive Gas Sampling System for Emission Sources (Tedlar® Bag Method)

Overview

The Tianhong TH-680 Passive Gas Sampling System is an engineered solution for standardized, field-deployable collection of gaseous emissions from stationary sources using the inertial passive bag method. Designed in strict accordance with Chinese environmental monitoring standards HJ 732–2014 (“Sampling of Volatile Organic Compounds from Stationary Source Exhaust Using Tedlar® Bags”) and HJ 38–2017 (“Determination of Total Hydrocarbons, Methane, and Non-Methane Hydrocarbons in Stationary Source Exhaust by Gas Chromatography”), the TH-680 enables compliant acquisition of NMHC (Non-Methane Hydrocarbons) and select VOCs—including aromatic hydrocarbons, aliphatic compounds, and oxygenated VOCs—prior to laboratory analysis via GC-FID, GC-MS, or FTIR. Unlike active sampling systems requiring continuous flow regulation and real-time mass flow control, the TH-680 operates on a pressure-differential-driven passive principle: vacuum-assisted filling of fluoropolymer gas bags (e.g., PVF or FEP-coated Tedlar®) ensures minimal analyte adsorption, low memory effect, and high sample integrity across temperature-sensitive matrices.

Key Features

• Integrated ergonomic handle design housing both heated sampling probe and precision vacuum control components—eliminating external cabling and inter-unit connections during field deployment.
• Imported PTFE three-way solenoid valve and brushless high-vacuum diaphragm pump deliver stable, pulse-free aspiration with six discrete flow rate settings (range: 0.1–2.0 L/min), calibrated per ISO 5167–1 for laminar flow consistency.
• Active heating system with PID-controlled thermal management; maximum setpoint: 180 °C, uniformity ±2 °C over full length of sampling line—preventing condensation and VOC loss in high-humidity or low-temperature exhaust streams.
• Dual-path pneumatic architecture: dedicated inlet gas path and independent vacuum chamber evacuation path operate simultaneously without manual valve switching—reducing operator error and improving sampling repeatability.
• Modular vacuum chamber configuration: supports user-selectable chamber volumes (1 L, 3 L, 5 L, 10 L, or 12 L); standard configuration includes 10 L chamber optimized for 5 L fluoropolymer gas bags (ASTM D6196-compliant).
• Real-time vacuum pressure monitoring via integrated digital transducer (range: −100 to 0 kPa, resolution: 0.1 kPa); automatic termination at preset negative pressure threshold or manual override capability.
• Post-sampling controlled venting: programmable or manual atmospheric equilibration of vacuum chamber—enabling rapid, contamination-free bag removal and minimizing exposure time for operators.
• Automated probe purge cycle: built-in timed sequence for post-sample cleaning using ambient or zero-air purge—ensuring cross-sample carryover remains below method detection limits (MDL) defined in HJ 732–2014 Annex B.

Sample Compatibility & Compliance

The TH-680 is validated for use with certified fluoropolymer gas bags meeting ASTM D6196 specifications for VOC stability (e.g., PVF, FEP-laminated Tedlar®). It complies with national regulatory frameworks governing emission source monitoring in China, including mandatory adherence to HJ 732–2014’s procedural requirements for bag preparation, leak testing, blank verification, and transport stabilization. While not certified to EU EN 13649 or US EPA Method TO-14/TO-15 by default, its operational parameters—including inert wetted path materials, temperature-controlled sampling train, and documented pressure decay performance—are fully compatible with GLP-aligned laboratory workflows supporting ISO/IEC 17025 accreditation. Data logs and sampling metadata (start/stop time, vacuum pressure profile, temperature history) are timestamped and exportable for audit readiness under internal QA/QC protocols.

Software & Data Management

The TH-680 features an embedded microcontroller with non-volatile memory for storing up to 500 sampling events. Each record captures vacuum pressure vs. time, heater setpoint and actual temperature, pump runtime, and operator ID (via optional RFID badge integration). Export is supported via USB-C interface in CSV format—structured to align with LIMS ingestion templates used in environmental testing laboratories. Firmware supports remote calibration parameter updates and diagnostic self-tests (valve actuation, pressure sensor zeroing, thermal ramp validation). All stored data includes cryptographic hash signatures to satisfy basic data integrity requirements under GLP and internal audit policies—though native 21 CFR Part 11 compliance requires integration with validated third-party electronic lab notebook (ELN) systems.

Applications

• Regulatory NMHC and VOC sampling from industrial stacks, incinerators, chemical reactors, and wastewater treatment off-gas lines.
• Pre-concentration support for canister-based GC analysis where bag sampling serves as primary capture prior to cryo-focusing or thermal desorption.
• Source apportionment studies requiring parallel multi-point grab sampling across facility perimeter zones.
• Method validation and field blank assessment per HJ 732–2014 Section 7.3 (transport and storage blanks) and HJ 38–2017 Section 8.2 (field duplicates).
• Emergency response deployments where rapid setup, battery-operated portability (optional external Li-ion pack), and minimal consumables reduce logistical overhead.

FAQ

What gas bag materials are compatible with the TH-680?
PVF (polyvinyl fluoride), FEP-coated Tedlar®, and other fluoropolymer films meeting ASTM D6196 Class I specifications are recommended. PVC, polyethylene, or uncoated Mylar® bags are not suitable due to VOC permeation and adsorption risks.
Does the TH-680 support automated calibration verification?
No standalone calibration gas injection port is included; however, the system supports manual leak-check procedures per HJ 732–2014 Section 6.4 using certified zero air and pressure decay monitoring.
Can the TH-680 be used for moisture-laden flue gases?
Yes—when operated with heated sampling line (up to 180 °C) and appropriate inline moisture traps (e.g., Nafion® dryers), provided condensate is removed upstream to prevent pump damage.
Is firmware update capability available in the field?
Yes—updates are delivered via signed firmware packages loaded through USB-C; version history and changelogs are retained in device memory for traceability.
What is the typical service interval for the vacuum pump?
Under normal operation (≤4 hrs/day, ≤30°C ambient), the brushless diaphragm pump requires maintenance every 12 months or 2,000 operating hours—whichever occurs first—as specified in the Maintenance Manual Rev. 3.1.