PM10 MASS Flow Controlled
In 1971, The Environmental Protection Agency (EPA) promulgated primary and secondary national ambient air quality standards for particulate matter measured as “total suspended particulate” or “TSP”. In accordance with the Clean Air Act, the EPA reviewed and revised the health and welfare criteria upon which these primary and secondary particulate matter standards were based.
On March 20, 1984 the EPA proposed changes in the standards based on it's review and revision of the criteria. On July 1, 1987 the EPA promulgated its final decisions regarding these changes. The final decisions include:

Replacing TSP as the indicator for particulate matter for the ambient standards with a new indicator that includes only those particles with an aerodynamic diameter less than or equal to nominally ten (10) microns (PM10).

A new Federal Reference method for measurement of PM10 in ambient air. The Reference method for the measurement of atmospheric particulate matter is known as PM10 and is based on selection of PM10 particles by internal separation, followed by filtration and gravimetric determination of PM10 mass on the filter substrate.

PM10 Volumetric Flow Controlled
The Volumetric Flow Controller (VFC) is a dimensional venturi device used to control gas flow. When applied to a high volume air sampler, this flow control principal incorporates a smooth-wall venturi orifice that gradually opens to a recovery section. Vacuum is provided by a motor downstream of the venturi. Over 95% of the energy lost in differential pressures across the restricting orifice is recovered in this design.

Flow control is accomplished by occluding or restricting and thus accelerating the air flow through the venturi . At some point in the flow stream, the air velocity will equal the acoustic velocity or speed of sound, and critical flow will be achieved. As long as downstream changes are small, all conditions at the venturi (including the flow rate) are determined by upstream conditions. This condition is referred to as “chocking” and is a distinctive characteristic of all VFCs. The GMW PM10/VFC utilizes this principle of choked or critical flow to maintain a constant actual flow rate of 40 ACFM (1.3ACMM) over the sample period. Since critical flow through the venturi is not greatly affected by changes in the filter loading, ambient temperature oo barometric pressure, a stable volumetric flow rate is maintained as long as power is provided to the sampler blower motor.

The orifice used in this system can also be described as a well documented Critical Venturi Meter (CVM). Basically, a CVM is a specially machined nozzle or restriction device designed to react to a specific pressure ratio expressed in absolute terms. When air reaches the speed of sound in the throat (smallest diameter) of the CVM, a sound pressure barrier is set up that will not allow more air through under the existing temperature and pressure conditions. This is the “critical flow” point of the meter, thus the name Critical Venturi Meter. Simply put, the Volumetric Flow controller regulates flow at a constant but unadjustable rate without any moving parts or electronic components. GMW PM10 Samplers bear an identification label with the FRM designation number RFPS-1287-063.

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TSP Mass Flow Controlled
All Andersen High Volume Air Samplers feature accurate collection of total suspended particulates exceeding EPA specifications. Air flow through a mass flow controlled system is maintained at a constant rate by an electronic probe which automatically adjusts the speed of the sampler to correct for variations in voltage temperature, pressure and filter loading. Adjustable over a range from 20 SCFM to 60 SCFM the air flow is controlled at constant standard conditions of 25 degrees C temperature and 760 mm Hg pressure within plus or minus 1 SCFM. By maintaining an exact air flow rate through the sampler, the average concentration measured is extremely accurate and reliable.

A typical Andersen TSP high volume air sampler incorporates a pressure recorder (G105) or a well-type manometer (G8WT) for flow verification. An elapsed time indicator (G901) is calibrated in hours, tenths, and hundredths meeting Federal Register specifications Vol 47 No. 234. Andersen sampling systems simplify all phases of the sampling process. Initial calibration requires no disassembly of the system.

TSP Volumetric Flow Contolled
The Volumetric Flow Controller (VFC) is a dimensional venturi device used to control gas flow. When applied to a high volume air sampler, this flow control principal incorporates a smooth-wall venturi orifice that gradually opens to a recovery section. Vacuum is provided by a motor downstream of the venturi. Over95% of the energy lost in differential pressures across the restricting orifice is recovered in this design.

Flow control is accomplished by occluding or restricting and thus accelerating the air flow through the venturi. At some point in the flow stream, the air velocity will equal the acoustic velocity or speed of sound, and critical flow will be achieved. As long as downstream changes are small, all conditions at the venturi (including the flow rate) are determined by upstream conditions. This condition is referred to as “choking” and is a distinctive characteristic of all VFCs. The Andersen TSP/VFC utilizes this principle of choked or critical flow to maintain a constant actual flow rate over the sample period. Since critical flow through the venturi is not greatly affected by changes in the filter loading, ambient temperature or barometric pressure, a stable volumetric flow rate is maintained as long as power is provided to the sampler blower motor.

The orifice used in this system can also be described as well documented Critical Venturi Meter (CVM). Basically, a CVM is a specially machined nozzle or restriction device designed to react to a specific pressure ratio expressed in absolute terms. When air reaches the speed of sound in the throat (smallest diameter) of the CVM, a sound pressure barrier is set up that will not allow more air through under the existing temperature and pressure conditions. This is the “critical flow” point of the meter, thus the name Critical Venturi Meter. The GMW Volumetric Flow Controller regulates flow at a constant but unadjustable rate without any moving parts or electronic components.

The PUF (Polyurethane Foam) Sampler is a complete air sampling system designed to simultaneously collect suspended airborne particulates as well as trap airborne organic vapors at flow rates up to 280 liters per minute. The PUF Sampler is equipped with a bypass blower motor arranged with an independent cooling fan. This feature permits the motor to operate at low sampling flow rates for extended periods without motor failure from overheating.

A dual chambered aluminum sampling module contains both filtering systems. The upper chamber supports the airborne particulate filter media in a circular a filter holder. The lower chamber encapsulates a glass cartridge, which contains the Polyurethane Foam for vapor entrapment.

A wide variety of sorbents can be used in a manner that permits their continual use. Polyurethane foam or wet/dry granular solid media can be used individually or in combination. The dual chambered sampling module designed for easy access to both upper and low media. The threaded lower canister moved with the cartridge intact for immediate exchange. Filter support screens and module components are equipped with gaskets providing a leak proof seal during the sampling process.

Airflow rates are infinitely variable up to 280 liters per minute. The voltage variator adjustment screw alters the blower motor speed to achieve the desired flow rate. Air flow rate is measured through the flow venturi utilizing a 0-100” Magnehelic Gage. Periodic calibration is necessary to maintain on-site sampling accuracy

A seven day mechanical timer is included as standard equipment and permits weekly scheduling with individual settings for each day and 14 trippers to turn the sampler on and off. Any day or days may be omitted and day and night periods are distinctly marked. Other timers and programmers are available optionally to suit any sampling requirement.