Beta Attenuation Mass Monitor

What is the Beta Attenuation Mass Monitor?

A continuous monitor that measures PM mass by the attenuation of beta radiation through dust collected on a filter tape. It is the reference-grade choice for regulatory PM10 and PM2.5 monitoring networks and industrial fence-line stations.

Overview

The beta attenuation monitor draws a known volume of air through a size-selective inlet and deposits particles on a spot of filter tape positioned between a carbon-14 source and a detector. Beta particles are absorbed in proportion to the mass on the tape, so the difference between a blank and a loaded measurement gives the mass concentration. The tape advances automatically to a fresh spot each cycle, typically hourly, which avoids the sample loading limits of fixed filters. A heated inlet or smart dryer controls humidity, because particle-bound water would be counted as mass. Internal flow control, temperature, pressure and barometric sensors normalise the sampled volume to standard conditions. Because the measurement is mass-based, the instrument compares well with gravimetric reference methods and is accepted in many national networks. Filter tape consumption and periodic leak and flow audits are the main routine services.

How does it work?

Particulate monitors use several physical principles. Beta attenuation monitors deposit particles on a filter tape and measure the attenuation of beta radiation from a carbon-14 source, which is proportional to deposited mass. Tapered element oscillating microbalance instruments weigh particles continuously on a filter mounted on an oscillating element whose frequency falls as mass accumulates. Optical monitors measure light scattered by particles at one or more angles and convert the signal to mass using an assumed or calibrated factor. High-volume samplers draw air through a size-selective inlet and a pre-weighed filter, giving a gravimetric result that serves as a reference. Condensation particle counters grow ultrafine particles in a supersaturated vapour and count them optically. Size-selective inlets such as cyclones or impactors define the cut point.

What are the key features?

• Beta radiation attenuation gives mass-based results comparable with gravimetric methods.
• Automatic filter tape indexing provides hourly data without manual filter changes.
• Heated inlet or smart dryer removes humidity bias from particle-bound water.
• Internal flow, temperature and pressure control normalises sampled volume.
• Size-selective cyclone or impactor inlets define PM10, PM2.5 or TSP cut points.
• Filter spot is retained for optional laboratory analysis of composition.

What are the technical specifications?

A typical beta attenuation mass monitor configuration offers measurement principle of Beta ray attenuation, carbon-14 source, size fractions of PM10, PM2.5, TSP (inlet dependent), measurement range of 0–1000 µg/m³, lower detection limit of < 1 µg/m³ (1 h), sampling interval of 30–60 min, user selectable and sample flow rate of 16.7 L/min. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Beta Attenuation Mass Monitor is used in national PM2.5 and PM10 networks, industrial fence-line compliance stations, background and roadside monitoring and network audit and co-location studies. Across the wider Particulate Monitors class, laboratories also deploy it for ambient PM10 and PM2.5 monitoring networks, industrial fence-line dust monitoring and indoor and occupational dust exposure checks.

Which standards and certifications apply?

Relevant standards and methods include EN 12341, US EPA 40 CFR Part 50 Appendix L, ISO 23210, ISO 10155, HJ 653 and GB 3095. Certification candidates for this model are CE, US EPA equivalent method approval and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Site the monitor so the inlet is 2 to 15 m above ground, away from walls, vents and trees that distort airflow, and record the inlet height. For beta attenuation and TEOM instruments, replace filter tape or cartridges on schedule and perform leak checks and flow audits with a primary standard. Keep the heated inlet and drying system working, since moisture control is critical to accuracy. For gravimetric samplers, equilibrate filters in a controlled weighing room at 20 to 23 °C and 30 to 40 percent relative humidity before and after sampling. Log operational status and invalid data flags, and co-locate new instruments with a reference monitor for field comparison before reporting.

How do I select the right Beta Attenuation Mass Monitor?

Select this monitor for regulatory mass data where hourly resolution and gravimetric comparability are required. Optical monitors are cheaper for screening but need correction. In an RFQ, specify the size fraction, inlet type, humidity control, flow rate and approval status required by the local authority.

How does it compare with other Particulate Monitors variants?

Choose the monitor by the metric and the purpose. For regulatory PM10 and PM2.5 mass data, beta attenuation or TEOM instruments approved under US EPA or EN methods are used, with gravimetric samplers for reference and auditing. For worker exposure, indoor checks and network densification, low-cost optical monitors give fast indicative results but need correction against reference data. Consider the size cut point, measurement range, averaging time and whether the instrument reports mass or number. Evaluate sampling inlet conditioning, since relative humidity above about 60 percent can bias optical and beta readings through particle growth, so heated inlets or naffion dryers are often fitted. Confirm filter or tape consumption and the calibration and audit schedule.