The UL Product Safety Audit: Inside the Process
William D. Webb
Being prepared for an unannounced UL audit is key to maintaining
UL certification and using the UL mark.
Getting the UL mark is a rigorous process. Once a manufacturer has
earned the right to place the UL mark on a product, it is equally important
to maintain its UL product report to ensure its continued UL listing.
To verify compliance, UL uses a Follow-Up Services Procedure. This
procedure includes unannounced and nearly unrestricted access to a manufacturer's
production facility where listed products are fabricated, assembled,
tested, stored, and shipped. As part of the procedure, a detailed description
of the product (the UL report) is used as a point of comparison during
these unannounced examinations of a listed product.
Under this program, UL field representatives conduct unscheduled quarterly
audits in an assigned territory, setting up and coordinating each audit.
Because the audits are not announced to the manufacturers, this task
can be challenging. Auditors must be flexible, creative, and sometimes
lucky to make the whole process work. This article presents an overview
of the UL audit process, including how to prepare for it and how to
implement precautionary measures. It also presents a case study of an
actual UL audit.
Preparing for an Audit
Update UL Product Report. To prepare for an audit, the first
order of business is to verify that all UL file changes and report updates,
if applicable, have been added to the manufacturer's UL product report.
These changes include component substitutions, additions, or deletions
requested by the manufacturer. Such design changes are generally triggered
by product upgrades, obsolete parts, performance improvements, and cost
When a manufacturer requests a change, UL will review the change, update
its report, and send a copy of the updated report's affected pages (with
implementation instructions) to both the manufacturer and the UL representative.
If the manufacturer has not implemented report updates before an unannounced
audit, the UL representative generally allows time to implement such
updates before continuing with the audit.
The Audit Process
On the day of an unscheduled facility visit, the UL representative
may arrive at any time to perform the product safety audit (see
Figure 1). The cognizant compliance person (compliance or agency
engineer or other person responsible for product safety compliance issues)
gets the call from the switchboard. The compliance person should be
ready at all times and be in a position to set aside other tasks to
focus on the audit process and the UL representative. Together, they
determine an appropriate action plan that will allow the auditor to
review the selected product. The size, complexity, number of problems
encountered, and number of UL-listed products due for inspection dictate
the amount of time required for the audit.
Although the UL representative may have a specific product in mind
for review and audit, extenuating circumstances can preclude an audit
of the selected product. One problem with an unannounced audit is that
the chosen product may not be in production at the time of the visit.
In this case, a product that is in production could be substituted,
provided that product is also UL listed. To continue, however, the UL
representative must have on hand the UL report for the alternate product;
otherwise, the audit is over. The auditor usually returns within a few
Once a UL representative becomes familiar with a manufacturer's production
cycles, audit rescheduling becomes less frequent and eventually unnecessary.
As a remedy for this anomaly, however, UL plans to institute two new
procedures in 2002. The first calls for the UL representative to contact
the manufacturing facility to identify anticipated production dates.
The second, called production ready audit, involves checking
a manufacturer's readiness for a UL audit. Under the new program, when
a product to be audited is not in production, the UL representative
will instead perform a production ready audit. The new procedures are
expected to minimize the number of rescheduled audits.
Verifying Compliance. The UL representative conducts the audit
using UL's Follow-Up Services Procedure, which prescribes required actions
and specific responsibilities. Manufacturers should be ready to present
well-documented agency reports.1
Most audits take place on the production floor, or wherever the audited
product is assembled and tested. Most UL auditors follow the flow of
the report (see Figure 2). At this stage, the UL representative verifies
compliance of the product and its components and assemblies based on
the information given in the UL report. The report includes photos of
both external and internal portions of the product and a detailed description
of relevant components. Each listed item is identified with a numbered
balloon and an arrow or line indicating its location on the photo (see
Figure 3). For each numbered balloon, a corresponding item number and
descriptive paragraph details component specifications as well as any
agency (UL, CSA, etc.) recognition, listing, or certification.
Figure 2. UL safety basic audit sequence.
|Figure 3. Representation of a picture with balloon
numbering system typically used in a UL report.
Plastic Parts. Plastic components such as line cords, panels,
bezels, meter housings, consoles, and touch panels are often shipped
in bulk to a warehouse or stockroom and therefore must be audited to
ensure that the appropriate markings appear on each item. To verify
compliance for such parts, the UL representative makes special arrangements
to view them.
Controlling compliance of polymeric components involves instituting
a set of procedures that includes vendor cooperation. It is the manufacturer's
responsibility to provide verification of compliance to the UL standard.
For example, if the UL representative is unable to verify line-cord
compliance locally, the vendor for that cord must be contacted and asked
to verify compliance in writing. Verification usually entails providing
a copy of the UL yellow card or similar document. The document can be
faxed or e-mailed to satisfy the audit process. This yellow card (or
reference page) comes from a listing of all UL-recognized and -listed
parts. The list is available in book form, and on UL's Web site (http://www.ul.com).
Noncompliance issues are not limited to obvious technical problems,
such as the use of a component that does not appear in the product's
UL report. Other problems can arise, and they must all be addressed
quickly. It is important to note that if a problem is identified, manufacturers
should take the time to correct it completely. Many labor-hours can
be wasted if the same issues must be addressed repeatedly. Closure is
essential in any audit process.
For this audit, the product selected a tabletop centrifugewas in
production. However, as a precaution, the UL representative brought
UL reports for all products listed for the company. The centrifuge was
listed to UL standard 3101. The auditor's primary task was to compare
the component data listed in the report with the actual components and
assemblies being used in production.
The product went through the first few sections of the report with
all descriptions, mechanical measurements, and primary components (power
input cords, power entry modules, circuit breakers, power transformers)
matching the product as listed in the report. Similarly, all secondary
components (relays, sensors, printed circuit components) matched the
report with no discrepancies.
The UL representative, however, noticed that one printed circuit board
(PCB) was not labeled with a flame rating (see sidebar). The PCB part
number was in place and correct but there was no indication, as required
by UL, of the material's flame rating. Although some sort of marking
was visible on the PCB, it could not be identified as either a rating
or a logo, even under magnification. The company contacted the manufacturer
to resolve the problem, and thus complete the audit and avoid a variation
notice. Upon investigation, the PCB manufacturer found that the logo
was on the product, but it had been photographically reduced so much
that it became unrecognizable. The PCB manufacturer was able to confirm
compliance in writing. In addition, the PCB manufacturer took responsibility
to correct the problem.
Because the centrifuge manufacturer was able to reconcile the compliance
issue while the UL representative was at the site, no variation notice
was issued. This concluded the audit.
If the compliance of all questionable components could not have been
verified in writing (or otherwise confirmed) while the UL representative
was at the facility, a variation notice would have been issued. Once
such a notice is issued, a UL program engineer reviews the circumstances
to determine whether to allow the manufacturer to continue to use the
UL mark. Continued use requires that a manufacturer provide proof of
compliance within 15 days (at the discretion of the services engineer).
Printed circuit board (PCB) material (e.g., G10) is a polymeric,
and it must be labeled with a flame rating to satisfy UL requirements.
The flame rating per UL 94 defines a polymeric part's resistance
to fire. Typical ratings for PCB material are 94V-1 or better.
The lower the number, the higher the flame rating (e.g., 94V-0
has a higher rating than 94V-1).
The flame rating is indicated in one of two ways. The flame
rating itself is printed, in clad, on the PCB (94V-1 etc.) or
the PCB manufacturer's logo is printed, in clad, on the board.
If a PCB manufacturer is UL authorized, its company logo can
be traced back to UL's authorized PCB manufacturers list. To
be authorized in this category, a PCB manufacturer is subject
to independent UL inspections of its manufacturing process and
All polymeric components must be flame rated and the rating
must be verifiable.
Alternatively, use of the UL mark could be delayed until UL verifies
that the product is in compliance. If compliance cannot be verified
after an agreed-upon time and no compromise can be reached, the UL listing
for that product could be terminated. It could be reinstated if a resolution
were reached between UL and the manufacturer. The noncompliant component
or assembly type and its effect on the product's overall safety often
dictate the consequences of a nonconformance.