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73
characteristics, etc.) and, consequently, determine the choice among acceptable
filters. Furthermore, certain types of filters may not be suitable for use with some
samplers, particularly under heavy loading conditions (high mass concentrations),
because of high or rapid increase in the filter flow resistance that would exceed the
capability of the sampler's flow control device. However, samplers equipped with
automatic filter-changing mechanisms may allow use of these types of filters.
The specifications given below are minimum requirements to ensure acceptability of
the filter medium for measurement of PM10 mass concentrations. Other filter
evaluation criteria should be considered to meet individual sampling and analysis
objectives.
7.2.2 Collection Efficiency. >/=99 percent, as measured by the DOP test (ASTM-2986)
with 0.3 micro-m particles at the sampler's operating face velocity.
7.2.3 Integrity. +/-5 micro-g/m3 (assuming sampler's nominal 24-hour air sample
volume). Integrity is measured as the PM10 concentration equivalent corresponding
to the average difference between the initial and the final weights of a random sample
of test filters that are weighed and handled under actual or simulated sampling
conditions, but have no air sample passed through them (i.e., filter blanks). As a
minimum, the test procedure must include initial equilibration and weighing,
installation on an inoperative sampler, removal from the sampler, and final
equilibration and weighing.
7.2.4 Alkalinity. 0.5 m3/min). Lower volume samplers (flow rates).
7.3 Flow Rate Transfer Standard. The flow rate transfer standard must be suitable for the sampler's
operating flow rate and must be calibrated against a primary flow or volume standard that is
traceable to the National Bureau of Standards (NBS). The flow rate transfer standard must be
capable of measuring the sampler's operating flow rate with an accuracy of +/- 2 percent.
7.4 Filter Conditioning Environment.
7.4.1 Temperature range: 15 to 30 C.
7.4.2 Temperature control: +/- 3C.
7.4.3 Humidity range: 20% to 45% RH.
7.4.4 Humidity control: +/-5% RH.
7.5 Analytical Balance. The analytical balance must be suitable for weighing the type and size of
filters required by the sampler. The range and sensitivity required will depend on the filter tare
weights and mass loadings. Typically, an analytical balance with a sensitivity of 0.1 mg is
required for high volume samplers (flow rates > 0.5 m3/min). Lower volume samplers (flow rates
< 0.5 m3/min) will require a more sensitive balance.
8.0 Calibration
8.1 General Requirements.
8.1.1 Calibration of the sampler's flow measurement device is required to establish traceability of
subsequent flow measurements to a primary standard. A flow rate transfer standard calibrated
against a primary flow or volume standard shall be used to calibrate or verify the accuracy of
the sampler's flow measurement device.
8.1.2 Particle size discrimination by inertial separation requires that specific air velocities be
maintained in the sampler's air inlet system. Therefore, the flow rate through the sampler's inlet
must be maintained throughout the sampling period within the design flow rate range specified
by the manufacturer. Design flow rates are specified as actual volumetric flow rates, measured
at existing conditions of temperature and pressure (Qa). In contrast, mass concentrations of
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