Because important and even critical information—electrical rating, warning, cautionary statements or marking, or even installation instructions—is sometimes printed on a label, the standards require at minimum an endurance test to be performed on the label to ensure the printed text and graphics do not smudge or disappear after many handlings. This article reviews the different aspects of labels and some of the applicable tests performed on a label.
Underwriters Laboratories (UL) is among the few National Recognized Test Laboratories (NRTL) that have a comprehensive database of different label suppliers, label materials, and label categories. Also, UL has produced UL 969, Marking and Labeling Systems, the Canadian equivalent of which is CAN/CSA C22.2 No. 0.15, Standard for Adhesive Labels. Note that the Canadian standard is not harmonized with its U.S. counterpart.
Although these standards are North American based, they are respected globally. UL 969 basically describes some of the tests such as the legibility test, defacement test, adhesion test, temperature test, and exposure-to-different-agents test. UL 969 covers four categories: PGDQ2, PGJI2, PGGU2, and PGJI2.
Most product safety standards, such as UL 60950-1, UL Standard for Safety for Information Technology Equipment Safety Part 1: General Requirements, or UL 60065, UL Standard for Safety for Audio, Video and Similar Electronic Apparatus Safety Requirements, require the label on the product to be tested for endurance during the type test or qualification test. UL standards typically refer to UL 969 for matters relating to labels. IEC standards use label endurance tests as outlined below.
The endurance test is typically a simple test that involves rubbing the label surface first with a cloth soaked with water for 15 seconds and then with a piece of cloth soaked with petroleum spirit for 15 seconds. The test is said to be satisfactory if the marking is still legible and the label cannot be removed easily without any sign of curling, wrinkling, shrinkage, or loss of adhesion around the perimeter. Unfortunately this test is not very repeatable, especially if the result is marginal.
UL classifies labels in the following categories:
- PGIS2 – Marking and labeling system, limited use (May not necessary comply with UL 969)
- PGDQ2 – Marking and labeling systems
- PGJI2 – Printing materials
- PGGU2 – Marking and labeling systems materials
PGIS2
This category covers label and cord tags that have been evaluated for compliance with the requirements in specific UL end-product standards where the performance requirements are different from those in UL 969. Labels in this category are intended for application to very specific products, such as Christmas tree light strings, extension cords, electrical boxes, and cabinets. These labels are typically used to provide warning instructions.
The PGIS2 category covers finished printed labels and unprinted label material used to make printed labels. This category is very limited in scope. Such labels are not recognized for general applications and have limited use.
PGDQ2
PGDQ2 is the first label category that was developed by UL. This category pertains to a finished preprinted label and is probably one of the most popular and commonly used label categories.
PGDQ2 evaluates a system consisting of ink, label stock, over-lamination, adhesive, and more to determine if they are compatible together when exposed to various temperatures, certain environments, and when applied to various surfaces. As a general rule these labels are sold as finished printed labels. See an example of the UL PGDQ2 label requirements in Figure 1.
Figure 1: PGDQ2 Classification Example
In this example, the Type A, B and C labels have been classified for use on different surfaces listed in the table. The label can be used as long as the label is used indoors in an environment between the maximum and minimum temperatures for each surface.
PGJI2
This category relates to a blank label stock or preprinted stock that has been evaluated together as a system and is similar to PGDQ2 except the end-user does the printing with the compatible ribbon inks that are matched to the label stock. The vendor has the label stock tested with various ribbon inks and for application to certain surfaces while exposed to various temperatures.
Typically, the label printing machines are not specified by UL if using a thermal or mechanical method for applying the ink. PGJI2 vendors usually sell the entire system as a package consisting of the printer, ribbon, and label stock.
When printing in-house, the label must use the PGJI2 system that is compatible with the material, environment, and temperature to which it is applied. The label stock should only be used with the specific ribbon or printer called out in the UL directory. The label stock and ribbon should be identified by the vendor as specified in the UL Certifications Directory. See an example of the UL PGJI2 label requirements in Figure 2.
Figure 2: PGJI2 Classification Example
In this example, the label type SW200, SW300, and SW400 have all been classified for use on different surfaces listed in the table. However the end user must use ribbons/ink type B1000 and S2000 from Company X and Y when printing on label material SW200 and SW300 but can only use ribbon/ink type S2000 when printing on label material type SW400. The labels can be used indoors in an environment between the maximum and minimum temperatures for each surface.
PGGU2
This category is limited to the individual parts of a system, such as over-lamination material, adhesive, or blank label stock excluding ink.
This category would be utilized by the label manufacturer in putting together a system. These products are usually sold to the label manufacturer in blank form for the purpose of creating printed label. One of the main benefits of this category is that the label print manufacturer, or the end-product manufacturer who purchases these recognized materials, can receive the benefit of approvals such as temperature, surfaces, or exposure conditions for which the materials have been tested.
PGAA
This category refers to the “Authorized Label Suppliers Program” and deals with printing and/or distribution of the UL certification marks. This serves to inform the user that UL has authorized the label manufacturer to print the UL logo and other UL logo variations, such as control number or product category. Only the suppliers in this category are authorized to print labels with the UL mark.
This category gives the label manufacturer the legal authority to reproduce the UL trademark and does not concern itself with the label material. Labels in this category must only be distributed only to authorized customers.
Label Types
Underwriters Laboratories has two categories of label that falls under its Follow-up Services:
- Type L labels
- Type R labels
Type L Labels
Type L is primarily intended for life safety products and products where manufacturing quality control is more of a safety issue. Another type of product that requires type L is those products where there are many variables in the manufacturing such as cables.
The process for obtaining each types of label is different. For type L, the manufacturer sends a label purchase order to an authorized supplier and sends a copy to UL. UL requires review of the UL Mark layout for UL Marks that have not been previously ordered.
UL’s Label Center issues a UL authorization order to the supplier with the UL Mark layout, serial, or issue numbers, quantity to print, and shipping instructions. A copy of the authorization is also sent to the manufacturer. The authorized supplier prints the UL Marks and sends them as specified by UL on the authorization order.
The UL Label Center normally checks the label network for three main elements:
- Appropriate UL symbol/logo
- Product name (I.T.E, A/V, etc.)
- Four-character control number
It is recommended that the manufacturer supply a copy of the label artwork to the UL engineer responsible for the project who can further advise on other label contents, such as electrical rating, cautions or warnings, model numbers, and so on.
For Type L labels, serial numbers issued by UL are associated with specific locations. If a manufacturer is producing the same product in more than one location, each facility will receive its own labels with dedicated serial numbers.
Follow-Up Services (FUS) base their inspections on the quantity of the labels that are ordered. That is, if the quantity of the labels is high, it will result in more frequent visits by the FUS group.
NOTE: Due to the changing issue/serial numbers that are controlled by UL, each order for Type “L” Marks must be authorized by a UL Label Center.
Type R Labels
Type R labels are the more common of the two. The manufacturer submits the label artwork to the local UL Label Center. UL reviews the UL Mark design and provides an approval stamp if the layout is acceptable. The manufacturer provides a stamped UL Mark layout to the supplier for printing of the UL Mark. The authorized supplier prints Type “R” UL Marks and sends them directly to the manufacturer. In some case the manufacturer can print in-house if he has the appropriate label stock and ink.
The UL Label Center normally checks the label network for three main elements:
- Appropriate UL symbol/logo
- Product name (I.T.E, A/V, etc.)
- Four-character control number
It is recommended that the manufacturer supply a copy of the label artwork to the UL engineer responsible for the project who can further advise on other label contents, such as electrical rating, cautions or warnings, model numbers, and so on.
NOTE: Future orders may be placed directly to the supplier as long as the composition of the UL Mark elements does not change from the UL authorized stamped drawing.
Conclusion
In summary, when selecting a label, the following points needs to be considered:
- Application of the label
- Follow-up services traceability
In the first case, one would need to consider the surface to which the label is being applied to, the temperature and climatic condition to which it will be exposed, and finally the appropriate UL category. If selecting PGJI2, it is important to ensure that the compatible ribbon is selected.
In the second case, it is important that adequate traceability is in place for UL Follow-up Services. This means that the label packaging/spool should have the original material manufacturer brand name or trademark and material type designation printed on it. For PGJ12, in addition to these two items, the UL recognition mark must appear on the spool or packaging. Basically the UL identification on the product should agree with the individual vendor’s recognition in the UL Certification Directory.
There may be cases when a manufacturer selects a label type and material that does not come from any of the label categories. In such scenarios the label may be evaluated as an unlisted component and the end product standard also plays a role. 
September 2013
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Homi Ahmadi is the Compliance Engineering Manager at Extron Electronics in Anaheim, CA and has responsibility for Extron global regulatory compliance affairs. He has extensive background in compliance which includes product safety, EMC and environmental. He is a Sr member of IEEE and iNARTE product safety engineer. He has published numerous articles and conducted seminars both in the US as well as UK to aid manufacturers with product design and compliance activities. He is currently a member of IEEE Product Safety Engineering Society (PSES). He received his Bachelor’s Degree in Engineering from the University of Mid-Glamorgan in Wales-UK. He held the position of program chair at IEEE PSES in Orange County from 2008-2010 and again from 2013 to 2014. |
