AS NZS 3580.9.11:2016 pdf free.Methods for sampling and analysis of ambient air Method 9.11: Determination of suspended particulate matter- PM10 beta attenuation monitors.
3.3 Equivalent aerodynamic diameter (EAD) The diameter of a spherical particle of unit density 1 g/cm’which exhibits the same aerodynamic behaviour as the particle in question. 3.4 PM10 Suspended particulate matter consisting of particles having an EAD of less than 10 μm, which is passed by a size classifier having performance characteristics as defined in US EPA 40 CFR 53 Subpart D. 3.5 Range . Nominal minimum and maximum concentrations that a method is capable of measuring. The nominal range is specified by the lower and upper range limits in concentration units, e.g.0 to 10 000 micrograms per cubic metre (μg/m’). 3.6 Uncertainty A variable associated with the result of a measurement that characterizes the dispersion of the values that could be reasonably attributed to the measurand. NOTE: The variable may be, for example, a standard deviation (or given multiple of it), or the half-width of an interval having a stated level of confidence. ISO/IEC Guide 98-3 provides a basis of evaluating uncertainty in the output of a measurement system.
4.2 Limitations and interferences Errors in mass determination can be caused by irregularities in the spatial distribution of the stream of beta electrons and heterogeneous deposits of particulate matter due to a deterioration of the sampling system. Changes in atmospheric pressure and temperature cause the density of air between the source and the detector to change. This can affect the determination of the mass of particulate matter deposited on the filter. The error can be minimized by keeping the time between the measurement of I and I2 as short as possible and can be corrected by measuring the atmospheric pressure and temperature, or by use of a dual detection system; in the latter case, the result of the second measurement (I2) has to be recorded continuously as mass accumulates over time. The elemental and chemical composition of atmospheric particulate matter has a small effect on the value of the coefficient of absorption per unit of mass (k). The k value depends on the maximum energy of the beta radiation therefore its value depends on the radioactive isotope used. The effect of radioactivity in particulate matter is negligible for long-lived radioisotopes. However, in locations where low levels of radon and its daughters are present, the response of beta gauges may be affected. Some BAMs have inbuilt systems to correct for this type of interference. The magnitude of the error depends on the type of equipment used. In some sampling climates (high humidity and/or temperature), there is the potential for water to condense on the filter media causing artificially high readings. The use of a sample inlet heater can mitigate this problem; however, care needs to be taken to ensure the sample is not excessively heated so as to lose semi-volatile compounds in the particulate matter.AS NZS 3580.9.11 pdf download.