UL Certification

UL Certification

UL Certification

The USA market is huge and offers a massive potential to grow your sales.
However when you start to look in to it, the regulations seem to put up certain barriers.
Below is a simple explanation of the requirements;

Useful definitions:

We use some of the below acronyms in our article.These terms are commonly used in the product compliance sector.

NRTL - US Nationally Recognised Test Laboratory.

OSHA - Occupational Safety and Health Administration – part of the US Government’s Department of Labor. Duties include accrediting US NRTLs.

CFR - Code of Federal Regulations. US Federal regulations.

AHJ - Authority Having Jurisdiction. There are thousands are AHJs across the USA and they often set regulations at a local level e.g. county, city.

Hazloc - Hazardous Locations. Special safety requirements for products where there could be explosive environments due to flammable gases, dust, fibres etc.

UL - Underwriters Laboratories Inc. An example of a US NRTL. Some other US labs also hold the same or similar testing accreditation.

UL also writes product safety standards.

CSA - Canadian Standards Agency. A Canadian safety standards writing body and also and accredited NRTL for the USA (as well as Canada. Other labs also hold the same or similar testing accreditation.

FCC - Federal Communication Commission. A US government body that regulates and oversee telecoms sector and telecoms products including devices containing radio transmitters. Various levels of regulations and certain products in the USA must comply with FCC regs by law.

IC - Industry Canada. A Canadian government department that regulates and oversee telecoms sector and telecoms products including devices containing radio transmitters. Various levels of regulations and certain products in Canada must comply with IC regs by law.

SCC - Standards Council of Canada. Oversee Canadian standards making process and accredit Canadian certification bodies and test labs.

Mandatory Requirements

The USA operates a similar approval process to the EU whereby it is largely a self-declaration process. Yes, a self-declaration process! It is a common misconception that US NRTL approval is mandatory for sale in the US and Canada.

The US Code of Federal Regulations (CFR) which outlines the rules and regulations applicable in the USA makes for very convoluted reading and the interpretation is very difficult. However, UL went through a review process a number of years ago and hired a number of lawyers to determine the mandatory requirements for products going on sale in the USA, the feedback was that only Hazloc (hazardous location) equipment is mandatory for US NRTL certification. This information is freely published in UL literature and on their website. http://gma.ul.com/about/globalmarkets/us

However, issues start to arise with non-certified products when customers specifically request NRTL approval before they will buy, and also that site inspections by AHJ’s can be failed due to parts not being NRTL compliant. Therefore, it is important to know the industry that you are selling to and your client’s attitude regarding NRTL approval. It is imperative that you have adequate evidence to prove your product is safe in case of any unfortunate incidences or even lawsuits. In terms of demonstrating adequate product safety, the most complete way (also most expensive) to get access to North American market is by NRTL approval.

One should also check if US FCC regulations apply to the product as this can be mandatory and breaching the rules can lead to products being impounded at customs and even large fines being applied if a product on the market is not adequately FCC certified. Even with FCC regulations, a large number of products can be self-certified by the manufacturer. Products that intentionally transmit such as an internet router with wireless functionality must be FCC certified, registered, and an FCC identity number applied.

NRTL (Nationally Recognised Test Laboratory) 

OSHA is the division of the US government – Department of Labor, that qualifies testing facilities as NRTL’s. To become authorised as an NRTL, the test facility must demonstrate that they have the required equipment, technical knowledge and quality procedures to perform testing and certification of products to recognised standards. NRTL’s are similar to Notified Bodies within Europe (and indeed some US NRTLs also hold EU Notified Body status) and are able to provide approval marks such as the ones shown below;


UL has probably by far, the most commonly known product safety approval mark, for two main reasons:

1 – Many US safety standards that are applied to products are UL-authored standards. These same standards are applied by the other NRTL bodies too.

2 – Many local AHJ’s check sheets specifically refer to UL as the certification mark required where in truth, any NRTL mark could be applied.

These leads to a special kind of safety approval mark called a ‘Field Evaluation’ mark and these are useful in circumstances where the ‘Listing’ marks as shown above are not economical due to low volume or even one-off production. Field Evaluation marking process is simplified, but each and every piece of equipment to be Field Evaluated must be individually inspected by an NRTL Field inspector. The Listing marks shown above are applied at the manufacturing location covered by other procedures.

Due to the extremely wide variety of products and test standards available, it is not possible for a single NRTL to be approved to test and certify every type of product. Each NRTL will have a scope of recognition detailing standards to which the NRTL is approved to test and certify products to. The scope of recognition for all NRTL's is available to view on the OSHA website.


NRTL's are audited by OSHA each year to ensure continued compliance, at this time the NRTL may request an extension to its scope of recognition. A list of all NRTL’s can be seen below;


The NRTL Approval Process 

There are three main types of third-party certification for the USA and Canada;

1. Type approval – Whereby the product is evaluated and tested to a defined standard by the NRTL and a certification file is created and the certification mark can be applied. The manufacturer is subjected to quarterly (or bi-annual with some NRTLs) follow up inspection to ensure that the product originally evaluated is the same as the product being made i.e. if changes are made to a product that affect the file report then these changes must be evaluated by the NRTL before going in to production. If this is not done, non-conformity notices are raised and in the worst case, potentially product recall. This type of approval is intended for high volume items. It will likely cost in the region of £3.5k annualised to maintain a UL listing. Other NRTLs have similar charges - usually there is a fee payable per factory inspection visit If you have multiple products in the same file the cost does not increase. Follow up inspection costs are based on UL file number, category control number and manufacturing location. Again, other NRTLs will have similar costs but cost structuring may vary by NRTL body. Certain types of safety related changes to items in production will incur additional NRTL re-qualification costs; the NRTL must be notified in advance of any such proposed changes otherwise the approval could be invalidated.
2. Field evaluation – Whereby the product is evaluated on-site normally (although it can be pre-inspected if desired) and an approval mark is applied on location. This is usually a less onerous process compared to type approval, as normally testing is not carried out (the field inspector does not usually carry test equipment); it is usually a construction and component review. This is primarily intended for single items of high value, but small batches can also be certified in this manner. CSA do offer the service whereby the mark is applied in the UK before going to North America with a caveat that it may need to be inspected in the US as well depending on the AHJ. The UL process will always require a field evaluation to be done on user site and there is a space on UL’s field evaluation certification application form to enter the name of the local AHJ – who will be notified and given the option to attend the field inspection.
3. Limited Production Certification (not offered by all NRTLs) – Where by the product goes through the type approval process but is not subjected to quarterly audits but rather the certification body goes and evaluates the product when a batch say of 100 items are to be labelled. This is intended for lower volume lower value items such as luminaires, small control panels and so on.

A type testing process for a product generally consists of testing, inspection and certification.


Testing involves determining whether a sample or prototype (if it is not commercially representative, further testing may be needed) of the product meets the applicable requirements of one or more specific consensus-based, U.S. product safety test standards (such as UL 60950 safety standard for information technology equipment, incidentally, being replaced by UL 62368). This would include assessing the construction of the product i.e. creepage and clearance distances, access to live parts, fire enclosure, components used etc. and would also include physical testing such as temperature, dielectric, earth bond and fault tests and so on.


Inspection of the factory that manufactures, or will manufacture, the product to verify that the products resulting from production runs are, or will be, in conformance with the test standard's requirements.

The inspection will review quality procedures, purchasing procedures, test equipment required for production line testing and equipment calibration. The exact process various by NRTL but still meets the overarching requirements of the US government OSHA body.

AN IPI (initial Product Inspection) will need to be arranged for the first-off safety-marked product on the production line, and then routine quarterly (or bi-annual for some NRTLs) factory inspections will start.


Certification provides independent assurance that the product conforms to the specific test standard(s). The NRTL also authorizes the manufacturer to apply the NRTL's mark to each unit of the manufactured product.

A Field Evaluation process typically involves an inspection and certification process:


The NRTL engineer will visit the equipment once it has been installed in to its final destination and will take in to account how and where it has been installed as part of the field evaluation process. The engineer will evaluate the construction of the product / machine to ensure that it meets the relevant requirements and has been made using certified components where applicable. Components are an area that needs to be investigated thoroughly as many approved components have certain conditions of acceptability and must be used within these conditions to remain compliant. i.e. must be used within their certification ratings, not simply their manufacture rating as these can differ. Also suitably UL ‘Listed’ or ‘Recognised’ or ‘Classified’ (the approval difference can be crucial) components and devices must be selected from the correct category type, otherwise the product or equipment will fail the inspection; an example being a UL 1077 supplementary circuit breaker certified to UL 1077 standard being used in a part of the circuit where only a UL 489 Listed branch circuit breaker is acceptable for the task (in this instance, a risk or fire or shock hazard if the wrong type of device is used).


All being well, the inspector will provide and affix the field label during the visit and will give the go ahead on the day, a follow up report will be provided. If the unit is non-compliant the inspector will provide a list of non-conformities and once these have been resolved, the field mark can be applied.

FCC (Federal Communications Commission) 

FCC regulations apply to electrical and electronic products that may produce radio frequency emissions. There are two main types of products covered "intentional emitters" and "unintentional emitters" 

There are exceptions from FCC regulations for some unintentional emitters a list can be found in Title 47 of the CFR (code of federal regulations).

Any product that is covered by FCC regulations is required to undergo an equipment authorisation assessment. There are four categories of equipment authorisation


Verification is a procedure where the manufacturer makes measurements or takes the necessary steps to ensure that the equipment complies with the appropriate technical standards. Submittal of a sample unit or representative data to the Commission demonstrating compliance is not required unless specifically requested by the Commission 

Examples of devices subject to Verification include, but are not limited to Industrial, Scientific and Medical (ISM) equipment; business Class A computer equipment; TV and FM receivers. Devices subject only to Verification shall be uniquely identified

Declaration of conformity 

A Declaration of Conformity is a procedure where the responsible party as defined in Section 2.909 of the CFR, makes measurements or takes other necessary steps to ensure that the equipment complies with the appropriate technical standards. Submittal of a sample unit or representative data to the Commission demonstrating compliance is not required unless specifically requested.

Examples of devices subject to DoC include, but are not limited to Class B personal computers and peripherals; CB receivers; super-regenerative receivers; TV interface devices. Devices subject to DoC shall be uniquely identified.

Devices must be tested by a test laboratory accredited by the National Voluntary Laboratory Accreditation Program (NVLAP); the American Association of Laboratory Accreditation (A2LA); or an accredited laboratory designated by the Commission under the terms of a negotiated Mutual Recognition Agreement (MRA).


Certification is an equipment authorization issued by the Commission or by a designated Telecommunications Certification Body (TCB) based on representations and test data submitted by the applicant. 

Examples of devices subject to Certification which must be submitted to the Commission include, but are not limited to Ultra Wideband; Software Defined Radio; new technology. 

Examples of devices subject to Certification which must be submitted to a TCB are Computers and Computer Peripherals. 

Examples of devices subject to Certification which may be submitted to either the Commission or to a TCB include, but are not limited to cell phones; RF Light; Microwave Oven; RC Transmitters; Family Radio; Telemetry Transmitters; Wireless Phones and Walkie Talkies.

Telecommunications Certification body.

The commission may designate a TCB to approve equipment under the certification procedure based on an application with all the specified information. Testing is required to be carried out by a Telecommunications Certification Body. The TCB shall process the application to determine whether the product meets the FCC requirements and shall issue a written grant of equipment authorization. The grant shall identify the TCB and the source of authority for issuing it. 

Examples of devices subject to Certification which must be submitted to the FCC include, but are not limited to Ultra Wideband; Software Defined Radio; new technology. 

Examples of devices subject to Certification which must be submitted to a TCB are Computers and Computer Peripherals. 

Examples of devices subject to Certification which may be submitted to either the FCC or to a TCB include, but are not limited to cell phones; RF Light; Microwave Oven; RC Transmitters; Family Radio; Telemetry Transmitters; Wireless Phones; Walkie Talkies. 

Guidance from technical experts should be sort to determine the correct equipment authorisation procedure for your equipment.

FCC Class A and Class B Digital equipment

Unintentional radiators are further classified as Class A or Class B

Class A - A digital device marketed for use in commercial, industrial, or business environment 

Class B - A digital device marketed for use in a residential environment, but may also be used in a commercial, industrial or business environment 

Class B requirements are more stringent than that of class A as it is foreseen that they could interfere with a wider range of equipment. 

UL listed Vs. UL recognised 

A UL listed product is an end product which has been assessed by UL to show the manufacturer can produce a complete product that complies with UL requirements. 

A UL recognised product is a component or sub-product that has been assessed by UL to show that the manufacturer can produce a component that can be used in an end product that complies with UL requirements.

For example, a Metal Oxide Varistor – MOV - will be UL recognised as it cannot be used as a standalone item but is suitable for incorporation within other equipment. The end product in which the MOV is used may be UL listed. The recognition of the device may well define its classification and where it can be used as well as other specific technical details such as voltage / current rating etc. Designing-in UL recognised components to a product that is to be UL Listed is the correct procedure but care must be taken to use the correct category of components, and that it’s ‘conditions of acceptability’ fully meet requirements in the end product application.

Why choose Product Approvals? 

When seeking NRTL certification, there are many pitfalls for the unwary which can lead to considerable lost time and extra expense. The following steps need to undertaken to try an ensure a smooth as possible process to approval.

1. Determine which product standard is applicable to your equipment (this can sometimes get quite involved and discussion with the prospective NRTL may be needed) 

2. Review the product against standard requirements

3. Create a detailed engineering document pack. As a minimum this should include 

    a. List of safety critical components and materials

    b. Mechanical drawings, photos 

    c. Component approvals 

    d. Flammability ratings of plastics used within the construction 

    e. Wiring diagrams and schematics

    f. User/ service manuals

4. Select an NRTL to be used. When selecting a NRTL the points below should be considered.

    a. NRTL scope of recognition

    b. NRTL acceptability to end customer

    c. NRTL reputation in terms of being straightforward to deal with

    d. Testing location (large items may be able to be tested on your premises by mutual agreement) 

    e. Time scale 

    f. Cost 

With our years of experience in the demanding third-party product testing and certification process, Product Approvals Ltd are one of a select few companies that have the experience, ability and willingness to guide you through the process, or fully project manage the whole process for you.

The involvement of Product Approvals Ltd early in the process to find and assist in correcting concerns / areas of non-conformance, before the product is submitted for NRTL approval can be invaluable in time saved. We also have a well-equipped product testing laboratory that can be used to carry out pre-compliance tests for the US and Canadian approvals process, and also for EU CE marking requirements.

For further advice and assistance, please contact us on:

Tel: +44 (0)1588 620192

Email: info@productapprovals.co.uk