Standard: 2003 NELAC
Link to relevant standard
I'm trying to determine if NELAC requires that the weight sets used to verify balances prior to use MUST be Class 1.
TNI FINAL RESPONSE:
(Quality System Expert Committee/NELAP Accreditation Council, 3-x-11)
A laboratory may use any class to verify the balance if the weights are traceable to a national standard.
A Class 1 (or "S") weight is normally considered a reference standard, but may be used as a working standard. If the laboratory has designated the weight as a reference standard, the weight may only be used for calibration (i.e. calibrating/checking working standards).
Standards that are used for daily calibrations (188.8.131.52.1) must be traceable to NIST. The Class1 or “S” weights can be used to verify the working standards, since these are traceable to NIST.