In order to comply with Local Law 31, XRF lead testing must be performed by an EPA-certified lead inspector or risk assessor. XRF lead testing involves a surface-by-surface investigation to determine whether lead-based paint is present in a house, dwelling unit, or residential building. The inspector holds the XRF analyzer directly on each painted surface in order to take measurements, which are then classified based on EPA / HUD standards. Per Local Law 66, if the measurement is greater or equal to 0.5 milligrams per square centimeter (mg/cm2), it is classified as a positive reading for lead-based paint.In order to comply with Local Law 31, XRF lead testing must be performed by an EPA-certified lead inspector or risk assessor. XRF lead testing involves a surface-by-surface investigation to determine whether lead-based paint is present in a house, dwelling unit, or residential building. The inspector holds the XRF analyzer directly on each painted surface in order to take measurements, which are then classified based on EPA / HUD standards. Per Local Law 66, if the measurement is greater or equal to 0.5 milligrams per square centimeter (mg/cm2), it is classified as a positive reading for lead-based paint.

Sometimes readings may be considered inconclusive if they fall within a certain range, as specified by the manufacturer's Performance Characteris- tic Sheet (PCS) for each model of XRF lead-based paint analyzer. In such a case, or if XRF readings cannot be taken because some surfaces are uneven or damaged, paint chip samples must be collected and analyzed in an accredited laboratory.