Page:NIOSH Manual of Analytical Methods - 0600.pdf/3

 PARTICULATES NOT OTHERWISE REGULATED, RESPIRABLE: METHOD 0600, Issue 3, dated 15 January 1998 - Page 3 of 6

NOTE :	Do not allow the sampler assembly to be inverted at any time. Turning the cyclone to anything more than a horizontal orientation may deposit oversized material from the cyclone body onto the filter. SAMPLE PREPARATION: 8.	Remove the top and bottom plugs from the filter cassette. Equilibrate for at least 2 h in an environmentally controlled area or chamber. CALIBRATION AND QUALITY CONTROL: 9.	Zero the microbalance before all weighings. Use the same microbalance for weighing filters before and after sample collection. Calibrate the balance with National Institute of Standards and Technology Class S-1.1 or ASTM Class 1 weights. 10.	The set of replicate field samples should be exposed to the same dust environment, either in a laboratory dust chamber [8] or in the field [9]. The quality control samples must be taken with the same equipment, procedures, and personnel used in the routine field samples. Calculate precision from these replicates and record relative standard deviation on control charts. Take corrective action when the precision is out of control [8]. MEASUREMENT: 11.	Weigh each filter, including field blanks. Record this post-sampling weight, (mg), beside its corresponding tare weight. Record anything remarkable about a filter (e.g., visible particles, overloading, leakage, wet, torn, etc.). CALCULATIONS: 12.	Calculate the concentration of respirable particulate, (mg/m³), in the air volume sampled, (L): , mg/m³, where:

= tare weight of filter before sampling (mg), = post-sampling weight of sample-containing filter (mg), = mean tare weight of blank filters (mg), = mean post-sampling weight of blank filters (mg), = volume as sampled at the nominal flow rate (i.e., 1.7 L/min or 2.2 L/min).

EVALUATION OF METHOD: 1.	Bias: In respirable dust measurements, the bias in a sample is calculated relative to the appropriate respirable dust convention. The theory for calculating bias was developed by Bartley and Breuer [10]. For this method, the bias, therefore, depends on the international convention for respirable dust, the cyclones’ penetration curves, and the size distribution of the ambient dust. Based on measured penetration curves for non-pulsating flow [1], the bias in this method is shown in Figure 1. For dust size distributions in the shaded region, the bias in this method lies within the ± 0.10 criterion established by NIOSH for method validation. Bias larger than ± 0.10 would, therefore, be expected for some workplace aerosols. However, bias within ± 0.20 would be expected for dusts with geometric standard deviations greater than 2.0, which is the case in most workplaces.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition