Safety Meets Customization: Navigating Field Equipment Approval in the US

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Consumer CompactElectrical and ElectronicsJuly 02, 2025

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Electrical equipment used in the workplace must be ‘approved’ to relevant safety standards. At a time when US manufacturing is under pressure to increase productivity, what are the available options for businesses seeking code-compliant operations involving custom-built or modified equipment?

The US Occupational Safety and Health Administration (OSHA) requires that all electrical equipment used in the work environment be ‘acceptable,’ in accordance with established safety standards. Under 29 CFR 1910.399 (Definitions, Subpart S), ‘acceptable’ means equipment accepted, certified, listed, labeled or otherwise determined to be safe by a Nationally Recognized Testing Laboratory (NRTL), as outlined in 1910.7.

In practical terms, all electrical equipment used in the workplace must be evaluated by an NRTL, since OSHA will only consider equipment to be ‘acceptable’ if it is certified, listed or labeled:

Certified: indicates that a product has undergone rigorous construction evaluation and testing following applicable standards, conducted by a third-party accredited test agency or an NRTL. Upon successful completion of this process, the agency issues a certificate of compliance.

A common certification pathway is Limited Production Certification (LPC), an industry-recognized option that enables certification for a limited batch of products. Unlike full certification, LPC does not require ongoing factory surveillance or audits.
A product that is ‘certified’ may be categorized as ‘recognized’ or ‘classified’. These designations are typically used for components or products intended for use in end assemblies. They often come with specific conditions of acceptability – restrictions that define how and where the product may be used, based on the evaluation it underwent. These distinctions are critical for ensuring that products are used only in appropriate applications.

Listed: intended for high-volume manufacturing. Listed products go through the same rigorous evaluations and testing as a ‘certified’ product. Listed products are subject to ongoing compliance oversight. The manufacturer enters an audit program with the NRTL, and compliant products are labeled at the factory before distribution.

Labeled: for equipment that is not certified or listed, a field evaluation may be conducted by an NRTL. Ideally, this is performed by an accredited Field Evaluation Body (FEB), although OSHA does not currently mandate such accreditation. Upon successful evaluation, a Field Evaluation Label is applied to indicate compliance. This label is only valid when accompanied by the corresponding field evaluation report, which documents the procedures and findings used to confirm compliance and justify labeling.

It is worth noting that, within the industry, these terms are sometimes applied loosely. For example, ‘certified’ may be used to refer to a ‘listed’ product, and vice versa.

It is important to recognize that not all testing agencies operate under the same framework. Some may offer certification services without being recognized by OSHA as an NRTL. Partnering with an OSHA-accredited NRTL enhances the credibility of your product and supports broader regulatory acceptance. Therefore, it is essential to choose a compliance partner who not only understands the scope of their accreditation but also how their services align with your product’s overall market access strategy.

All electrical products used in the workplace must meet one of these safety pathways – certified, listed or labeled – to be considered ‘acceptable’ under OSHA regulations.

The role of the NEC

The National Electrical Code (NEC), also known as NFPA 70, is a consensus-based electrical code developed by the National Fire Protection Association (NFPA). It sets the benchmark for safe electrical design, installation and inspection practices. OSHA frequently references the NEC for guidance on compliance with electrical safety standards, especially under 29 CFR 1910 Subpart S and 1926 Subpart K.

Both OSHA and the NEC include almost identical clauses emphasizing the proper installation and use of electrical equipment based on manufacturer instructions and any instructions included in the listing or labeling:

OSHA 1910.303(b)(2) (Examination)
NEC Section 110.3(B) (Installation and Use)

These instructions are derived from the applicable product safety standards and are a critical part of the equipment evaluation process. This consistency between OSHA and the NEC highlights the importance of adhering to installation guidelines provided by manufacturers, which are based on recognized safety codes.

While the end user is responsible for adhering to OSHA guidelines and regulations, various governing bodies are involved in enforcement. Electrical inspectors, building officials and fire marshals, operating under local authorities (county, city or state), as well as other third-party inspection agencies, may hold final authority to approve the use of equipment by verifying that it meets OSHA and NEC requirements.

When certification or listing is not feasible

While NRTL certification or listing is the preferred route for many products, there are instances where this may not be feasible or practical. This may occur when the equipment is:

Custom-built, making it impractical to send a unique item to an NRTL for evaluation and certification
Modified or refurbished, thereby invalidating any prior approval
Imported for a specific purpose, but lacking NRTL certification

In such cases, field evaluations serve as a vital compliance mechanism. If machinery or equipment in the workplace lacks proper approval, the relevant US Authority Having Jurisdiction (AHJ) may red tag it, rendering it inoperable. To reverse this, a recognized and competent body must complete a successful field evaluation and apply a compliance label.

Product certification or field evaluation?

A common misconception is that field evaluation is equivalent to product certification. While both aim to ensure equipment safety and compliance with applicable codes and standards, they serve distinct functions. Product certification involves rigorous, standardized laboratory testing of a product line and includes ongoing oversight. Listed products undergo periodic audits and inspections by an NRTL to ensure all manufactured units continue to meet established safety standards.

In contrast, field evaluation is a one-time, site-specific assessment of a single piece of equipment. It is often used when the equipment is custom-built, modified or specially imported and is not part of a standardized, mass-produced line. Unlike product certification, field evaluation must occur on-site after the equipment is installed in its final location. The equipment cannot be portable or evaluated and pre-labeled before shipment. The evaluation process considers not only the equipment itself, but also its installation environment, to determine compliance with applicable safety standards.

It is important to understand that not all NRTLs are accredited to perform field evaluations. OSHA’s recognition of NRTLs pertains specifically to their ability to conduct product testing and certification, not field evaluations. Field evaluation requires a separate accreditation process governed by different standards and accrediting bodies. FEBs are typically accredited to the requirements of NFPA 790, which outlines the competency standards for third-party field evaluation organizations, and NFPA 791, which provides recommended practices and procedures for evaluating unlabeled electrical equipment.

This field evaluation accreditation is independent of OSHA’s NRTL recognition. It is ordinarily granted by approved accrediting bodies such as the American Association for Laboratory Accreditation (A2LA) or the International Accreditation Service (IAS).

Cybersecurity: a new challenge

One of the most significant changes impacting field evaluations is the addition of mandatory cybersecurity requirements in the 2024 edition of NFPA 79, Electrical Standard for Industrial Machinery, a standard commonly used in field evaluations. The new edition contains Section 4.10, which mandates cybersecurity controls for any equipment connected to a communication network and capable of controlling machinery. Given the growing reliance on networked systems, this requirement is crucial for protecting industrial operations from cyberattacks. Failure to comply with these cybersecurity requirements can result in costly delays, regulatory issues and increased risk exposure. A proactive compliance strategy is therefore essential for avoiding disruptions and ensuring secure and continuous operations.

SGS solutions

At SGS, we collaborate with AHJs to support stakeholder understanding and compliance with the NEC and evolving product standards. As an OSHA-accredited NRTL and an accredited field evaluation body, we provide comprehensive compliance services and continuous education, recognizing that both technology and standards are constantly evolving. Our support spans from early-stage design compliance consultation to final on-site inspections and labeling. Throughout the process, we support the development of products that meet relevant US regulations, minimizing disruption to project timelines. We not only have an expansive US-based team, but also deep US code and compliance expertise integrated across our global network.

With a team of cybersecurity experts, we also support clients in complying with NFPA 79, offering guidance on best practices, regulatory requirements and customized cybersecurity solutions. Our solutions help protect electrical equipment and industrial systems against both electrical hazards and cybersecurity risks, covering on-site devices, unlisted equipment, factory relocations and red-tagged machinery across commercial, industrial and residential sectors. Wherever a business operates in the US, our field evaluation services provide clarity and confidence, helping clients resume operations quickly and safely.

Learn more about our US Field Evaluation Services.