TH-β25 Beta-Ray Atmospheric Particulate Matter Monitor

Overview

The TH-β25 Beta-Ray Atmospheric Particulate Matter Monitor is a field-deployable, continuous ambient air quality instrument engineered for regulatory-grade monitoring of suspended particulate mass concentrations. It operates on the well-established physical principle of beta-ray attenuation—where low-energy beta particles (typically from a ¹⁴C or ⁸⁵Kr source) pass through a continuously advancing filter tape loaded with collected airborne particles. The reduction in beta particle flux, measured by a proportional counter or scintillation detector, is linearly correlated to the areal mass loading (µg/cm²) of particulate matter on the filter. By combining this real-time absorption signal with precise volumetric airflow measurement (via integrated mass flow sensor and temperature/pressure compensation), the system calculates and reports mass concentration in standard units (µg/m³) for multiple size-fractionated fractions—including Total Suspended Particulates (TSP), PM₁₀, PM₅, and PM_2.5. Designed to meet the functional requirements of environmental protection agencies, industrial hygiene programs, and academic atmospheric research laboratories, the TH-β25 delivers high reproducibility, minimal operator dependency, and compliance-ready data logging without requiring off-site gravimetric validation for routine operation.

Key Features

• Multi-fraction capability: Configurable sampling heads enable sequential or dedicated monitoring of TSP, PM₁₀, PM₅, and PM_2.5 per EN 12341, ISO 7708, and US EPA reference methods.
• Automated calibration verification: Integrated standard film insertion prior to each sampling cycle provides traceable attenuation baseline correction, mitigating long-term drift and improving inter-unit comparability.
• Precision filter transport: Optical encoder-based multi-position photodetector system ensures sub-millimeter positional accuracy during tape advancement—eliminating common mechanical failures such as paper slippage, misalignment, or jamming observed in legacy belt-driven systems.
• Intelligent power management: Non-volatile memory preserves all raw and processed data during unexpected power loss; automatic system reset and resumption of scheduled sampling occur upon power restoration, with no manual intervention required.
• Embedded microcontroller architecture: Real-time data acquisition, temperature/pressure-compensated flow calculation, and concentration derivation are performed onboard—minimizing external computational dependencies and ensuring deterministic response latency.

Sample Compatibility & Compliance

The TH-β25 accepts standard 40 mm or 80 mm diameter quartz fiber or cellulose ester filter media compliant with ISO 9096 and ASTM D1357. Its sampling inlet design adheres to the isokinetic aspiration criteria defined in ISO 21507 and EPA Method 201A for size-selective cyclones and impactors. While not certified to EU CE-MD or US EPA EQPM specifications out-of-the-box, the instrument’s measurement methodology aligns with the fundamental physics underpinning ISO 12103-1 (test dust standards), EN 14907 (ambient air—determination of PM mass concentration), and China’s HJ 653–2013 technical specification for β-ray absorption-based PM monitors. Data output formats support CSV and ASCII protocols compatible with national environmental monitoring networks (e.g., CNEMC platform integration).

Software & Data Management

The TH-β25 features an embedded 3.5-inch TFT LCD with bilingual (Chinese/English) menu navigation and real-time graphical display of concentration trends, flow rate, tape position, and system status. All measurement records—including raw beta counts, corrected mass loadings, volumetric flow, ambient temperature/pressure, and diagnostic flags—are stored internally in timestamped binary format with configurable retention (up to 30 days at 1-minute resolution). Optional RS-232/RS-485 and Ethernet interfaces enable remote configuration, firmware updates, and secure data export via Modbus RTU/TCP or custom TCP/IP socket protocol. Audit trails, user access levels, and electronic signatures are implemented in accordance with GLP principles; raw data files retain immutable metadata required for regulatory review under China’s “Measures for the Administration of Environmental Monitoring Data Quality” (MEP Order No. 39).

Applications

• Ambient air quality monitoring stations operated by municipal or provincial ecological environment bureaus.
• Industrial boundary and stack emission compliance verification for cement, steel, coal-fired power, and waste incineration facilities.
• Indoor air quality assessment in cleanrooms, hospitals, and educational laboratory environments where respirable fraction quantification is critical.
• Mobile monitoring platforms (e.g., vehicle-mounted or drone-deployed configurations) requiring low-power, vibration-tolerant particulate mass measurement.
• Method development and comparative studies between β-ray absorption and alternative techniques (e.g., TEOM, laser scattering) under controlled test conditions.

FAQ

What radioactive source is used in the TH-β25, and what is its activity level?

The instrument employs a sealed ¹⁴C beta source with nominal activity ≤ 37 kBq (1 µCi), classified as exempt from licensing under IAEA RS-G-1.9 and China’s GB 18871–2002 radiation safety regulations.
Does the TH-β25 require annual calibration by an accredited lab?

While field verification using NIST-traceable standard films is recommended quarterly, full recalibration against gravimetric reference samplers is advised annually per HJ 653–2013 to maintain metrological traceability.
Can the TH-β25 operate unattended for extended periods?

Yes—equipped with internal rechargeable backup battery (72 h runtime), SD card data storage, and watchdog timer circuitry, it supports fully autonomous deployment in remote locations with periodic telemetry polling.
Is the filter tape consumable supplied by the manufacturer only?

Standardized 40-mm glass fiber tapes (e.g., Pallflex TX40HI20WW) are commercially available; however, optimal performance requires tapes pre-conditioned to match the instrument’s humidity and static charge compensation algorithms.
How does the TH-β25 handle high-humidity or foggy conditions?

Integrated Nafion™-based permeation dryer and heated inlet line (maintained at 50 °C) minimize water vapor interference and prevent condensation on the filter surface, preserving beta absorption linearity per ISO 12103-1 Annex B.