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DESCRIPTION OF METHOD - APPENDIX J PART 50
Code of Federal Regulations July 1, 1998
Appendix J--Reference Method for the Determination of
Particulate Matter as PM10 in the Atmosphere
1.0 Applicability.
1.1 This method provides for the measurement of the mass concentration of particulate matter
with an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM10) in
ambient air over a 24-hour period for purposes of determining attainment and maintenance of
the primary and secondary national ambient air quality standards for particulate matter
specified in Sec. 50.6 of this chapter. The measurement process is nondestructive, and the
PM10 sample can be subjected to subsequent physical or chemical analyses. Quality
assurance procedures and guidance are provided in Part 58, Appendices A and B, of this
chapter and in References 1 and 2.
2.0 Principle.
2.1 An air sampler draws ambient air at a constant flow rate into a specially shaped inlet where
the suspended particulate matter is inertially separated into one or more size fractions
within the PM10 size range. Each size fraction in the PM10 size range is then
collected on a separate filter over the specified sampling period. The particle size
discrimination characteristics (sampling effectiveness and 50 percent cutpoint) of the sampler
inlet are prescribed as performance specifications in Part 53 of this chapter.
2.2 Each filter is weighed (after moisture equilibration) before and after use to determine the net
weight (mass) gain due to collected PM10. The total volume of air sampled, corrected to
EPA reference conditions (25 deg. C, 101.3 kPa), is determined from the measured flow rate
and the sampling time. The mass concentration of PM10 in the ambient air is computed as the
total mass of collected particles in the PM10 size range divided by the volume of air sampled,
and is expressed in micrograms per standard cubic meter (micro-g/ std m3). For PM10
samples collected at temperatures and pressures significantly different from EPA reference
conditions, these corrected concentrations sometimes differ substantially from actual
concentrations (in micrograms per actual cubic meter), particularly at high elevations.
Although not required, the actual PM10 concentration can be calculated from the corrected
concentration, using the average ambient temperature and barometric pressure during the
sampling period.
2.3 A method based on this principle will be considered a reference method only if (a) the
associated sampler meets the requirements specified in this appendix and the requirements in
Part 53 of this chapter, and (b) the method has been designated as a reference method in
accordance with Part 53 of this chapter.
3.0 Range.
3.1 The lower limit of the mass concentration range is determined by the repeatability of filter tare
weights, assuming the nominal air sample volume for the sampler. For samplers having an
automatic filter-changing mechanism, there may be no upper limit. For samplers that do not
have an automatic filter-changing mechanism, the upper limit is determined by the filter mass
loading beyond which the sampler no longer maintains the operating flow rate within specified
limits due to increased pressure drop across the loaded filter. This upper limit cannot be
specified precisely because it is a complex function of the ambient particle size distribution and
type, humidity, filter type, and perhaps other factors. Nevertheless, all samplers should be
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