The MerPAS^® sampler fitted with the yellow body diffusive barrier is best used for sampling outdoor ambient air with highly elevated mercury concentrations (50 ng/m³). This sampler has a thicker diffusive barrier, thereby reducing the effective sampling rate to lessen Hg capture by the device. The sampling time is typically hours up to 7 days, depending on the expected Hg levels and project goals. For general guidelines on the appropriate MerPAS^® sampling configuration, see the Estimated Sampling Intervals table in the attached document.