The two analytical methods for the measurement of crystalline silica is Fourier Transform Infrared (FTIR) and X ray diffraction (XRD).

FTIR is more prone to interferences and there is greater measurement uncertainty because the scanning area is about 8 millimetres where there may be significant differences in the dust deposition on the filter.

In comparison XRD uses the majority of the filter scanning about 20 millimetres in diameter the filter is also rotated which reduces the heterogeneity in measurement and consequently reduces the uncertainty.

The detection limits for FTIR and XRD can be comparable but XRD has the ability to adjust the scanning parameters by increasing the measurement time and thereby reducing the limits of detection 

FTIR is also limited to about 1 milligrams of dust loading where XRD can compensate for much greater than this up to about 4 mg or so.

With the reduction of the exposure standards there are some technical implications. The workplace exposure standards are generally assessed through a statistical analysis using the European standard 689 workplace exposure measurement of exposure by inhalation to chemical agents strategy for testing compliance with occupational exposure limits

XRD and FTIR are generally accepted but when it comes to low levels of RCS The detection limit becomes problematic and they use statistical analysis when determining compliance where this is problematic The European standard EN 482 states that the limit value of a chemical agent can be so low that no measuring procedure is available which meets the requirements and that the measuring procedure should be used that is closest to the specified requirements for this particular analysis

XRD is closer to the specified requirements at these lower limits and should be used in preference to FTIR due to its reduced limit of detection and better accuracy.