The NRTL Product Safety Inspection

William D. Webb

Being prepared for an NRTL inspection is essential, and preparation is an evergreen process.

The process of qualifying for a product safety certification from a Nationally Recognized Testing Laboratory (NRTL) can be challenging. After the manufacturer has complied with the certification requirements and NRTL has allowed use of its mark on a product, the completed NRTL report on the certified product becomes a live document; that is, in order for the product to retain certification to the NRTL mark, the NRTL report must be accurately maintained on an ongoing basis. Unlike the CE mark, which is a declaration by the manufacturer that all applicable product safety standards are met, the NRTL mark is allowed to be used at the discretion of NRTL. This process involves ongoing testing and verification.

To verify a product’s compliance with the relevant standard, the NRTL performs quarterly, biyearly, or yearly inspections. The formal requirement is four inspections per year, but certain factors can cause this number to vary. For example, the more noncompliance issues that come to light during product inspections, the more inspections the manufacturer can expect to undergo.

This article presents an overview of the NRTL inspection process. It discusses such topics as how to prepare for an inspection and how to properly make a change in an NRTL report. It also suggests some precautionary measures manufacturers can take to avoid falling into noncompliance and losing the NRTL marking.

The NRTL and the NRTL Report

In the United States, the safety agency most likely to be recognized as such by the average consumer is Underwriters Laboratories (UL). This is because UL has been around the longest and has the largest database of recognized and listed components and products. All NRTLs use UL’s standards or the European Norm (EN) equivalent. This article, in discussing NRTL reports, is essentially describing UL’s process even as it refers generically to “the NRTL.”

There are 17 other organizations besides UL that have received the NRTL safety agency accreditation. The accrediting agency is an office within the U.S. Occupational Safety & Health Administration (OSHA; Washington, DC). OSHA defines an NRTL as “an organization that OSHA has ‘recognized’ as meeting the legal requirements in 29 CFR 1910.7.¹ In brief, these requirements are the capability, control programs, complete independence, and reporting and complaint handling procedures to test and certify specific types of products for workplace safety. This means, in part, that an organization must have the necessary capability both as a product testing laboratory and as a product certification body to receive OSHA recognition as an NRTL.”

The OSHA Web site is a source of information about all NRTLs, including CSA, TÜV Rheinland, TÜV America, ETL, and CSL. The NRTL roster now includes several global agencies; it is not limited to U.S. organizations as it once was.

ISO 9000 Quality Management and Product Safety. Manufacturers’ quality management systems stand in close relationship to the product safety inspection process, which must be noted. Although a few NRTLs also offer ISO 9000 certification of quality systems, most do not. Those that do, enjoy a marketing advantage in that they can offer one-stop shopping to their customers by performing two services. Those that don’t may find the inspection process easier because it will likely be proceduralized already at the manufacturer’s end through an existing quality management system.

The process of generating and maintaining an NRTL report is handled pretty much the same by all recognized laboratories. However, report formats do differ. The NRTLs that offer both a quality system audit and certification for the NRTL mark may perform safety inspections less frequently and focus instead on the quality system. By contrast, labs that offer product safety testing only generally rely on quarterly inspections of individually certified or listed products.

Many manufacturers have their quality system certified by one agency or NRTL and obtain the NRTL safety certification mark from another. It is up to the manufacturer to decide which approach suits its business needs.

Compliance inspections by an NRTL generally are unannounced, and inspectors must be granted access to the manufacturer’s production facility where compliant products are fabricated, assembled, tested, stored, and shipped. Because the inspections are not always announced, the task can be challenging for inspectors, who must be flexible, creative, and sometimes lucky to make the whole process work (see later discussion of the inspection process).

Report Contents. The inspection procedure involves using the detailed description of the product in the NRTL report as a point of comparison. The content of the NRTL report varies among the recognized laboratories. UL, for example, has used product or assembly photos and related them to descriptive paragraphs in order to document component details. CSA and TÜV, on the other hand, use a list of specified critical safety items to verify compliance. All NRTLs place some form of Critical Safety Items page in the report, usually near the beginning.

UL has begun to move away from the descriptive report format and toward a CB Scheme–style format called Ultra-Link. In this new format, whenever the product is changed or updated, UL will be issuing an amendment to the report rather than revising the pages that are affected.

Some data items that can also be found toward the front of an NRTL report involve product marking and labeling. These include the manufacturer’s name, the product model number, power ratings, and the NRTL mark, as well as an indication of how to distinguish the exact date on which a product was manufactured. This last detail is important in cases for which there might have been a lapse in safety compliance. Keeping track of design changes using serial number breaks allows the questionable batch of product to be isolated and tracked for rework in order to maintain NRTL compliance.

This is where having an ISO 9000–certified quality system in place is effective. A certified system ensures that all data will be accurately recorded and that such records will be kept for a carefully specified period.

Among the more generic processes the NRTL inspector examines are the calibration and function of in-process and final-testing test equipment. Tests monitored at the in-process location are those involving setup and calibration. Tests monitored at the final-test location are those pertaining to electrical safety, such as dielectric strength and ground continuity.

Updating the Report. Manufacturers should update the NRTL report on a continuous basis. It cannot be emphasized too much that keeping the NRTL report up-to-date is an evergreen process, unceasing and always important.

The first order of business is to verify that all NRTL file changes and report updates, if applicable, have been added to the manufacturer’s copy of the report. When the report is first issued by the NRTL testing laboratory, it is a good idea for the manufacturer to perform its own audit to verify report accuracy. Changes made to the product report beyond that point in time will be billed to the manufacturer at the going rate. Some changes that must be monitored and documented might involve component substitutions, additions, or deletions. Such design changes can be triggered by a number of conditions and motivations, including a desire to upgrade the product; the necessity of replacing obsolete parts or introducing performance improvements for market competitiveness; and cost considerations. They all should go into the NRTL report.

Making a change in the NRTL report is a process that takes a team effort. R&D, manufacturing, purchasing, field service, and compliance personnel have to work together. When any one of these departments requires a design change or other modification that will affect the report, the report must be marked up to reflect the changes and then submitted to the NRTL, which must give its approval before the change can be implemented in the manufactured product. The NRTL reviews the modifications to determine whether any additional testing is required.

Figure 1. Procedure for making a product design change in an NRTL report.

After all action items are reconciled, the NRTL updates the report and sends a copy of the affected pages, with instructions for implementation of new requirements, to the manufacturer and to the NRTL field representative with responsibility for that manufacturer. If the manufacturer has not implemented updated action items in the report by the time of an inspection, the NRTL representative generally allows it time, on the spot, to implement the necessary changes before continuing with the inspection (see Figure 1).

The Inspection Process

On the day of a product safety inspection, the NRTL representative arrives unannounced. The manufacturer’s compliance contact person is notified. This may be a regulatory affairs professional, an engineer, or some other person on staff with responsibility for product safety compliance issues. Because the inspection is an event without warning, the compliance person should be ready at all times to set aside other tasks in order to focus on the inspection process and the needs of the NRTL representative. Together, the compliance person and inspector determine an appropriate plan for enabling the NRTL representative to review the selected product.

The amount of time required to complete the inspection will be dictated by the size, complexity, and number of problems encountered and by the number of NRTL-certified, -listed, or -recognized products due for inspection.

Although the NRTL representative may have a specific product in mind for review and inspection, extenuating circumstances can preclude examination of the selected product. One problem with an unannounced inspection is that the target product may not happen to be in production at that time. In such cases, a product that is in production may be substituted, provided that that product also is NRTL-certified or -listed. To continue along this path, however, the NRTL representative must have on hand the NRTL report for the alternate product. Usually, the manufacturer’s copy will be available.

Figure 2. The NRTL product safety inspection process.

In the past, this would have been the end of the inspection. The NRTL representative usually returned within a few weeks. In this age of laptops and portable PCs, the inspector generally has easy access to all NRTL reports for a given manufacturer. As the NRTL representative becomes familiar with a manufacturer’s production cycles, inspection rescheduling becomes less frequent and eventually unnecessary (see Figure 2).

Each NRTL has its own procedure for conducting on-site product safety inspections. They all have a follow-up services procedure, which prescribes required actions and specific responsibilities. For their part, manufacturers should be ready to present well-documented product safety reports.

The Case of Polymeric Components

Plastic components such as power cords, panels, bezels, meter housings, consoles, and touch panels are often shipped in bulk to a warehouse or stockroom. These components must be inspected to ensure that the appropriate markings appear on each item or each batch of items as required by the NRTL. To verify compliance for such parts, the NRTL representative will have to inspect them in the warehouse or other storage facility.

Verifying Compliance. Controlling compliance of polymeric components involves instituting a set of procedures that includes supplier cooperation. It is the manufacturer’s responsibility to provide verification of compliance to the relevant standard. For example, if the NRTL representative is unable to verify the flame rating of a plastic panel locally, the manufacturer must contact the vendor of that cord and ask for compliance verification in writing. This problem could have occurred because a bulk shipment of items such as these plastic panels arriving at the receiving department’s dock was repackaged for warehousing and the certification documentation was discarded (this can happen with bulk packaging of certain products).

Verification usually entails providing a copy of the UL-listed or -recognized documentation to the NRTL. The document may be faxed or e-mailed while the inspection is going on; this will satisfy the requirements of the process. This problem won’t happen with parts such as line cords and other mains-related wiring. These items are individually marked on their outer jacket with wire size, style number, and, in some cases, the file number as dictated by UL, CSA, etc.

Flame Rating. Printed-circuit-board (PCB) substrate material constitutes a polymeric part that must be labeled with a flame rating to satisfy UL 94 requirements.² The UL 94 rating defines the degree of a polymeric part’s resistance to fire. Typical ratings for PCB material are UL 94V-1 or better. The lower the number, the higher the flame rating; that is, UL 94V-0 is a better rating than UL 94V-1.

The component’s flame rating is indicated in one of two ways. The flame rating itself may be printed on the PCB, or the PCB manufacturer’s name and PCB type number may appear on the board or packaging. Through cross-referencing these markings with the documentation identified in UL’s directory for this type of component, verification is readily accomplished. If a PCB manufacturer is UL authorized, its company logo can be traced back to UL’s list of authorized PCB manufacturers. To be authorized in this category, a PCB manufacturer subjects itself to independent UL inspections of its manufacturing processes and materials. The part might be marked, but inadequately in terms of compliance verifiability.

The Case of the Too-Small Logo

A manufacturer of laboratory equipment was being inspected by an NRTL. During the process, the inspector noticed that one of the PCB assemblies had no visible UL flame rating or manufacturer’s PCB type number anywhere. Multiple boards with the same part number were checked; results were the same. The equipment manufacturer immediately called the PCB manufacturer, who in turn notified its PCB material supplier. The material vendor supplied the necessary UL directory documentation in writing to satisfy the NRTL representative. Further, final inquiry showed that the vendor had indeed placed the appropriate information on the board; however, it was photographically reduced beyond the point of recognition, being indecipherable even when magnified. So, all polymeric components must be flame rated and the rating must be verifiable.

Noncompliance issues are not limited to such obvious technical problems as the use of a component that does not appear in the product’s NRTL report. Other problems can arise, like the hyperreduced marking on the PCB. All such problems must be addressed quickly. It is important to note that if a problem is identified, the manufacturer should take the time to correct it completely. Many hours of labor can be wasted if the same issue has to be addressed repeatedly. Closure is essential in any inspection process.

Noncompliance

If the compliance of all questionable components cannot be verified in writing, or otherwise confirmed, while the NRTL representative is at the production facility, a noncompliance flag will be raised. In the case of UL, the inspecting agency issues a variation document. After such a document is issued, a UL program engineer reviews the circumstances to determine whether to allow the manufacturer to continue to use that laboratory’s NRTL mark. Continued use of the mark requires that the manufacturer provide proof of compliance within a finite time frame, which is usually within 15 days, at the discretion of the program engineer. Most NRTLs use methods of remedial action similar to those of UL.

Alternatively, permission for the manufacturer to use the NRTL mark on the product could be delayed until the NRTL is able to verify that the product is, in fact, compliant. If compliance cannot be verified after an agreed-upon time and no compromise can be reached, the NRTL marking for that product could be terminated. It can, however, be reinstated with resolution of the noncompliance issue. The nature of the out-of-compliance component or assembly and its importance to the product’s overall operational safety will dictate the punitive consequences. On the economic side, the monetary cost to the manufacturer in production downtime adds up very quickly. In any case, cooperation is instrumental in order to shorten the remedial process as much as possible.

One method commonly used to avoid unauthorized component changes is to stamp—in large letters—on each safety critical component drawing the following: “NOTE: Safety Critical Component. Do not change or substitute without the approval of the agency compliance department.” This is dictated by the NRTL report.

Conclusion

Manufacturers want to offer the market products that are certified for safety. The NRTL mark that signifies such certification is contingent on the product passing periodic inspections and on the product’s NRTL report being kept up-to-date. Verification of compliance is crucial. The bottom line is that the information in the report must match what the inspector finds in the product.

References

1. Code of Federal Regulations, 29 CFR 1910.7 [on-line] available from Internet: www.
gpoaccess.gov/cfr/index.html.
2. UL 94, “Tests for Flammability of Plastic Materials for Parts in Devices and Appliances (Northbrook, IL: Underwriters Laboratories, 2000).

Resources

Information about NRTLs is available from the Internet: www.osha.gov/dts/otpca/nrtl/index.html.

Information on UL-listed and UL-recognized components is available from the Internet: www.ul.com.

William D. Webb is a senior compliance engineer at Dictaphone Corp. (Stratford, CT) with two decades of experience in electromagnetic compatibility, safety, and telecom compliance. He can be reached at compliancehelp@yahoo.com.