June 2005 

Calibration of Rocks? 

Calibration Certificates--Acceptance or Not? 

By Georgia Harris 

A number of questions arise around the issue of acceptance of calibration reports from 

accredited calibration laboratories by States. Do you accept them or not? How do you 

know if they are okay to accept? What are the related issues? What are the steps to 

determine what is okay and what is not? 

First - you must determine whether your State laws (statutes, regulations, or rules) allow 

acceptance of calibration reports from other laboratories. This is usually under 

reciprocity agreements for registered/licensed service agents. Some State laws do not 

allow acceptance of calibration reports from other laboratories and doing so can be a 

violation of your own laws. Proposals for modifying the model laws in Handbook 130 

were developed to help States gain the authority for accepting calibration reports in a 

uniform and consistent way. 

Second - if your laws allow acceptance of calibration reports from other laboratories 

whether accredited or not, you need to determine which laboratories are covered (States 

only? Accredited only? All?). Determine whether the laboratory is accredited and 

evaluate which accreditation bodies are acceptable. All laboratories are not accredited or 

recognized. And, all accreditations are NOT equal! 

NIST recommends 1) only reports from accredited or recognized calibration laboratories 

be accepted and 2) the recognition or accreditation needs to come from NIST or a 

NACLA-approved accreditation body. NACLA is the North American Calibration 

Laboratory Association and is the body that ensures the quality of the accreditation. If a 

laboratory is not accredited or recognized, do not accept the calibration report. At this 

time, the only accreditation bodies who have been approved by NACLA are: NVLAP, 

A2LA, and L-A-B. There are many laboratories, including some manufacturers, who are 

not accredited or are not accredited by one of these bodies. 

Third - you need to evaluate the "scope of accreditation." The laboratory scope, which is 

published with the accreditation or recognition certificate, defines the parameters and 

associated uncertainties that have been assessed by the accreditation bodies. Many 

laboratories that are accredited, even by NACLA-approved bodies, still provide services 

that are NOT under their scope of accreditation. For example, a laboratory that is 

accredited to provide Class F calibrations may not be accredited to provide Class 1 

calibrations. Being accredited in general is not enough. The laboratory scope must cover 

the level of service that is needed. In addition, many accredited laboratories have 

services that are under their scope, but they do not provide a full "accredited calibration." 

Certificates of Accuracy and Traceability Certificates are generally not under the scope 

and should not be accepted. An accreditation body logo should be on anything that is 

accepted. 
Finally, States must retain the authority and right to oversee the evaluation of standards 

used in weights and measures activities. Accreditation does NOT provide any assurance 

that the standards identified in a calibration report are suitable for the intended 

applications. For example, a laboratory that is accredited by a NACLA-approved 

accreditation body could have the calibration of ROCKS on their scope and be able to 

meet their stated uncertainties. BUT, that doesn't mean that the ROCKS comply with the 

field standards requirements for weights used in evaluating scales for compliance to 

Handbook 44 (e.g., Class F). The State must still evaluate standards to ensure suitability. 

States also need to retain the rights to revoke acceptance of certificates for cause (bad 

measurement results).