Calibration: The comparison of a measurement instrument or system of unverified accuracy to a measurement instrument or system of known accuracy to detect any variation from the required performance specification.
–American Society for Quality

It is absolutely essential that calibration be an integral part of a food or ingredient processor’s quality and safety program. Almost all regulations and management standards that address food quality and safety include language that stresses the importance of calibration. The low-acid canned food regulations found in the U.S. Code of Federal Regulations 21 CFR Part 113 reference the need for calibration:

“Each thermometer should have a tag, seal or other means of identity that includes the date on which it was last tested for accuracy.”

As does the Hazard Analysis and Critical Control Points (HACCP) regulations that are mandated for meat and poultry, seafood and juice:

“Records that document the calibration of process monitoring instruments.”

And, finally, ISO 22000, the food safety management system’s requirements for any organization in the food chain, states in Section 8.3:

“The organization shall provide evidence that the specified monitoring and measuring methods and equipment are adequate to ensure the performance of the monitoring and measuring procedures.”

The bottom line is that all instruments used for ensuring quality, safety, sanitation and legal compliance must be calibrated. In addition, if there are monitoring devices that are necessary to ensure worker safety and/or safe operation of equipment, they must be included in the calibration program. An example of such a device would be a pop-off valve on a pressure vessel.

To achieve this goal, processors need to perform the following:

• Develop effective procedures for calibration;
• Document those procedures;
• Maintain records of calibration activities, including corrective actions;
• Review records to ensure that procedures are being followed;
• Observe the employees doing the calibration procedure to ensure they are following the procedures; or, audit third parties contracted to do similar work.

It is also important to assign someone to manage the calibration program to ensure that it is properly designed, implemented and maintained.

Who Manages the Program?
So, who should manage the calibration program? This depends on each and every company. What happens frequently is that processors do not assign an individual to manage the calibration program, but allow it to be done by different operating groups. The production people might be responsible for unit operations such as metal detectors or magnets, whereas engineering takes responsibility for temperature-indicating devices (TIDs) and pressure gages. The quality manager or laboratory supervisor will ensure that the instruments in the laboratory are properly calibrated. There may be other groups that get involved. For example, the warehouse people might be responsible for looking after refrigerators, freezers and relative humidity controls.

What can happen in a situation like this is that there are many different calibration programs that use different forms and procedures. In addition, there may be critical instruments that “fall through the cracks” and are either not being calibrated or not being calibrated frequently enough to adequately ensure safety or quality. It is okay to have different persons responsible for their areas, but one person needs to manage the entire program. His or her role is to ensure that there is a consistent program that addresses all calibration activities that need to be done to ensure product quality and safety. The calibration manager needs to work with his group to establish a standard format for procedures. The manager must also evaluate all monitoring instruments in the plant and determine not only whether calibration is necessary, but how often this should be done. By conducting a risk assessment, they can determine not only which devices are essential for the production of safe, wholesome and high-quality products, but also whether the procedures are being employed properly.

The job description of the manager responsible for calibration should clearly state that this individual is responsible for managing the program. He or she must accept their job description, acknowledging responsibility. Among their duties will be to ensure that the program remains on schedule, that it is audited per established schedules and that calibration records are being reviewed per established schedules. In addition, the calibration manager must ensure that all persons responsible for calibrating instruments or ensuring that they are calibrated have been trained on the procedures and/or work instructions required to do the work and that records of these sessions are maintained.

Developing and Documenting Procedures
It is absolutely imperative that all procedures involved in the calibration program be documented. There should be a general protocol that describes how the calibration program will be developed and implemented, plus work instructions that describe how each instrument or class of instruments should be calibrated.

The general protocol should include the following elements:

• Objective of the program
• Responsibility
• Calibration procedures
• Documentation responsibilities
• Corrective actions

Each work instruction should include step-by-step procedures on how the calibration should be done, the standards that will be employed, the tolerances and how the results shall be reported. If the instrument is out of calibration, the procedures must not only describe what will be done with the instrument, but more importantly, it must address what to do with any product that might be affected. Most operations “tag” their instruments after calibration. The calibration tag may include who did the work, the date the work was done and the date of the next scheduled calibration. These tags should be made of materials that are water- and oil-resistant so they will survive the rigors of production, including cleaning. Additionally, if tagging is part of the program, removal of outdated tags and replacement with new ones should be included in the procedures.

With instruments such as pressure gages or TIDs, it is best to calibrate the unit at three points that bracket the normal operating parameters. The risk assessment exercise should be used to help establish how to calibrate the instrument.

There is a difference between calibration and verification. Perhaps the best example to use when differentiating the two is a scale. Scales are usually calibrated one or two times per year by a regulatory agency or a licensed calibration organization. These groups test the units against known standards and adjust them as needed. Many operations routinely verify their scales. To do this, they routinely check performance using standard weights.

Calibration procedures must address instruments used for monitoring process operations and performing quality tests, and any standards used in-house. Processors must send standard thermometers (National Institute of Standards and Technology or American Society for Testing and Materials), weights and other devices to an outside agency for calibration at regular intervals.

Procedures for sending instruments out must also be documented. If a state agency comes into your facility once a year to calibrate scales, load cells and other devices, procedures describing how this is done, who is responsible and what needs to be done if the instrument is found to be out-of-calibration are necessary.

One of the most valuable tools for documenting and organizing a calibration program is a master calibration schedule (Table 1). Rolling all instruments that require calibration into this master list allows a processor to easily monitor the program and makes life much easier for auditors. The whole program is summarized in one document. Of course, hard copy records of calibration records must be available for review and to verify that the work was not only done, but done properly.

Records and Corrective Actions
Records of all calibration activities must be maintained either as hard copies or electronically. Many processors roll their process instrument calibration into a maintenance management software program. These systems are available commercially or can be developed internally using programs such as Excel™ or Access™. If your company decides to purchase or build an electronic system to maintain and monitor a calibration program, consider incorporating the following features:

• Maintenance scheduling
• Flags when items are due
• Flags for past-due items
• Procedures for doing work
• Automatic entry by workers
• Ability to have records scanned and accessed by the system
• Ability to verify that work has been done
• Print capability: summaries, schedules
• Ability to “talk” to other systems

Be forewarned, however, electronic maintenance management systems take a great deal of time and effort to get up and running. There is a huge amount of information to input into the system. In addition, it is absolutely imperative that several persons be trained to manage and use the system. This is one situation where “putting all your eggs in one basket” can be huge mistake. I have seen such systems abandoned when the only trained person leaves the company.

As noted above, calibration records are mandatory for all instruments used to monitor Critical Control Points (CCPs) in a HACCP program. In addition, the importance of developing documented calibration procedures that include corrective actions cannot be overemphasized. One of the gaps observed in many calibration programs is that the corrective actions do not include what to do with product that may be affected. The protocol may contain statements like the following:

“If the instrument is not in calibration, make the necessary adjustments to bring it back into calibration and retest,” or

“If the instrument is out-of-calibration, take it out of service and send it to the vendor for repairs. If it cannot be repaired, replace it immediately.”

It is imperative that the procedures address any product that might be affected. Here is an example: many years ago, a processor of acidified peppers, a seasonal item, received a visit from the U.S. Food and Drug Administration (FDA) at the end of the season. The company’s records indicated that all of the products packed throughout the season had a pH of 4.6 or below. When the FDA began checking the pH values of products, they found pH values of 4.8 and above. These findings indicated that the product was potentially unsafe as it could support the growth of Clostridium botulinum. Unfortunately, the company had no records documenting that their pH meters had been calibrated. The company said that they did it each and every day, but they had failed to document that the work had been done. The FDA told them to embargo the entire season’s pack and develop a sampling plan to show compliance. The company elected to destroy the entire season’s pack, estimating that the testing would cost too much. So in this case, a failure to maintain proper calibration records cost a company a full season’s pack.

There are many instruments or pieces of equipment that processors look to outside agencies to calibrate, which may include scales, load cells, TIDs and others. If an outside agency does the work, make sure that their reports include the method used for calibration, tolerances, any adjustments or actions and results. Simply sending a report that the instrument is satisfactory is unacceptable.

Record/Review Verification of the Program
The pepper packer scenario discussed above is an excellent example of the importance of record review. Management must develop a program to review all calibration records deemed critical to quality and safety by the risk assessment. Procedures on how to review the records should be developed and implemented. In addition, employees who conduct the reviews must be trained on said procedures. For CCPs, review of the records for calibrating the instruments would be incorporated into the HACCP plan.
Processors should also establish programs to verify that the calibration program is being properly followed. Persons doing these internal audits should be independent of this area. For example, if calibration is managed by the production group, the auditor could be drawn from quality, warehouse operations or elsewhere. The verification activities should include the following elements:

• Procedures – The auditors should make sure that the persons responsible for doing work are following established proce- dures. Auditors should use procedures and work instruc- tions as a guide when doing this phase of the audit. Auditors should also look to see that calibrations were car- ried out according to schedule.

• Competencies/Training – This starts with the auditor reviewing the training records. However, training should lead to competencies. To verify the latter, the auditor needs to observe the individual doing the calibration to determine if the person is actually following the procedure. When work is done by an outside agency, confirm that the group doing the work is competent and that there is some protocol for selecting and evaluating potential contractors.

• Records – The auditors should also review records, which would include looking for deviations and corrective actions. The review should also look for evidence of management

The individuals conducting these audits must be trained on audit procedures. In addition, records of training must be maintained. This is something that may be done internally or through an outside agency. Many processors send their people to programs that certify them as ISO auditors. Again, this is a choice that each company should make.

Evaluating the Program
Calibration and, in fact, all programs should be evaluated on a regular basis. The program should be reviewed by the plant manager and the management team at least once a year. The review should draw heavily on the verification activities and on the company’s performance related to quality and safety goals. The objective of this exercise is to look at the program as it exists and look for ways to enhance it. One of the results of the management review should be an improvement plan that includes programs, assigned responsibilities, timelines to complete the project and the resources needed to complete the work. If such a program has been operating, the review should also address past improvement plans, their status and success or failure. This is an essential element for continuous improvement and an integral element of ISO 22000.

Making the Calibration Program “Audit Friendly”
As mentioned, calibration is an integral part of a processor’s quality and safety program. Getting the program organized, particularly ensuring that it is managed by one person rather than many, will help make the program “audit friendly.” The master calibration schedule provides users and auditors with an organized summary of the program. In fact, to make it even easier to manage, processors should add one more field: the location of the records for that instrument. Of course, the best means for getting everything in one place is an electronic system. As noted, maintenance management software programs are a tool that can capture the whole program; so rather than looking at piles of records, one can audit the complete program by sitting in one place in front of a computer. If electronic systems are used, the computer should have security systems that meet 21 CRF 11, the electronic recordkeeping requirements.

So, take a long look at how calibration programs are being managed and ask yourself, “Is this the best we can do?” My guess is that you can do better.

Richard F. Stier is a consulting food scientist with international experience in food safety (HACCP), plant sanitation, quality systems, process optimization, GMP compliance and microbiology. Among his many affiliations, he is a member of the Institute of Food Technologists and an editorial advisor to Food Safety Magazine. He can be reached at