NOTE: There is an alternative to scanning an area air sample, settled dust sample, or ground bulk
sample to prove lack of contamination. A slow scan of the three main peaks of quartz (also
cristobalite and tridym ite if their absence has not been previously confirmed) on a personal air
sample, with verification that their intensity ratios are within 15% of pure quartz, is sufficient
evidence that other materials are not interfering in the silica determination.
12. Perform the following for each sample, working standard, and blank filter:
a. Mount the reference specimen. Determ ine the net intensity, Ir
, of the reference specimen before
and after each filter is scanned. Use a diffraction peak of high intensity that can be rapidly but
reproducibly (Sr