TSP High Volume Air Samplers

All TSP hi-vols feature accurate collection of total suspended particulates according to U.S. EPA specifications. Hi-vols have been used extensively in Federal, state and industrial monitoring networks for the measurement of ambient air quality standards for TSP and are used widely for occupational health monitoring and particulate research studies.

PRINCIPLE OF OPERATION
The high volume air sampler collects suspended particulates on large 8 x 10-inch (20.3 x 25.4cm) filter media. The name high volume is appropriate because the sampling flow rate has a high level of 20 to 60 standard cubic feet per minute (SCFM), or 0.57 to 1.71 standard cubic meters per minute (SCMM). Because of the high flow rate, large quantities of particles ranging from 0.1 to 1 gram are collected over a typical 24-hour sampling period. This facilitates gravimetric and chemical analysis and is the advantage hi vol samplers have over other air sampling methods.

FLOW CONTROL SYSTEMS
Two types of flow control systems are available. One is mass flow control (MFC), while the other is volumetric flow control (VFC).

• The flow rate in a MFC system is actively sensed and controlled at some pre-determined set point. Air is pulled through the filter into the intake of a blower and subsequently exits the sampler through an exit orifice, which facilitates measurement of the flow with a manometer or pressure recorder. The flow rate is controlled by an electronic mass-flow controller, which uses a flow sensor installed below the filter holder to monitor the mass flow rate and to control the speed of the motor accordingly. The controlled flow rate can be changed by an adjustment knob on the flow controller.


• A VFC system maintains a constant volumetric flow rate (given a fixed temperature) through the inlet, rather than a constant mass flow rate as in the MFC system. A choked-flow venturi is operated such that the air attains sonic velocity in the throat of the device. In this "choked" mode, the flow rate is unaffected by downstream conditions such as motor speed or exit pressure, and is a predictable function of upstream conditions, such as stagnation pressure ratio and temperature. Thus, the volumetric flow is controlled without any moving parts or electronic components. With this type of flow control system, no means is provided for adjusting the controlled flow rate.

• Hi-Vol Cascade Impactor
• Hi-Vol Filter Media

Meets U.S. EPA 40 CFR Part 50, Appendix B - Reference Method for the Determination of Suspended Particulate Matter in the Atmosphere (High-Volume Method)