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ASTM D 6246 Document Information:
Title
Standard Practice for Evaluating the Performance of Diffusive Samplers
ASTM International
Publication Date:
Apr 1, 2008
Scope:
This practice covers the evaluation of the performance of
diffusive samplers of gases and vapors for use over sampling
periods from 4 to 12 h and for wind speeds less than 0.5 m/s. Such
sampling periods and wind speeds are the most common in the indoor
workplace setting. This practice does not apply to static or area
sampling in wind speeds less than 0.1 m/s, when diffusion
outside the sampler may dominate needed convection from
the ambient air to the vicinity of the sampler. Given a suitable
exposure chamber, the practice can be extended to cover sampler use
for other sampling periods and conditions. The aim is to provide a
concise set of experiments for classifying samplers primarily in
accordance with a single sampler accuracy figure. Accuracy is
defined (3.2.1) in this standard so as to take into account both
imprecision and uncorrected bias. Accuracy estimates refer to
conditions of sampler use which are normally expected in a
workplace setting. These conditions may be characterized by the
temperature, atmospheric pressure, humidity, and ambient wind
speed, none of which may be constant or accurately known when the
sampler is used in the field. Futhermore, the accuracy accounts for
the effects of diffusive loss of analyte on the estimation of
time-weighted averages of concentrations which may not be constant
in time. Aside from accuracy, the samplers are tested for
compliance with the manufacturer's stated limits on capacity,
possibly in the presence of interfering compounds.
This practice is an extension of previous research on diffusive
samplers (1-14)2 as well as Practices D 4597, D 4598, D
4599, and MDHS 27. An essential advance here is the estimation of
sampler accuracy under actual conditions of use. Futhermore, the
costs of sampler evaluation are reduced.
Knowledge gained from similar analytes expedites sampler
evaluation. For example, interpolation of data characterizing the
sampling of analytes at separated points of a homologous series of
compounds is recommended. At present the procedure of (9) is
suggested. Following evaluation of a sampler in use at a single
homologous series member according to the present practice, higher
molecular weight members would receive partial validations
considering sampling rate, capacity, analytical recovery, and
interferences. The test for diffusive analyte loss can be omitted
if the effect is found negligible for a given sampler or analyte
series.
The values stated in SI units are to be regarded as standard. No
other units of measurement are included in this standard.
This standard does not purport to address all of the safety
concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and
health practices and determine the applicability of regulatory
limitations prior to use.
Keywords:
- accuracy
- air monitoring
- bias
- concentration
- diffusive
- evaluation
- gases
- passive
- performance
- precision
- sampling and analysis
- samplers
- tests
- uncertainty
- vapors
- workplace atmospheres
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