3rd Party Field Label Evaluation

Our skilled field technicians can perform your Field Label, safety label your equipment and produce the required report for the city quickly and efficiently.

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Field Labeling Quick Topics

Watch How We Perform Field Evaluations

In this video, field engineer Oleg Zholudev and PE Doug Snow provide information and visual context to our company’s 3rd party field evaluation services that Lewis Bass is proud to offer our clients.

What is 3rd Party Field Labeling?

Field labeling is a safety review. Although its main area of interest is electrical, other important aspects of machine and operations safety are also covered in the labeling/permitting process. There are particular codes that are followed by all 3rd Party Inspectors, which do not vary.

These codes are as follows:

  • NFPA 70 – (The US “National Electrical Code”, which writes the rules for electricity)
  • UL 508A – Safety of Industrial Control Panels
  • NFPA 79 – Electrical Standard for Industrial Machinery
  • NFPA 791 – Recommended Practice and Procedures for Unlabeled Electrical Equipment Evaluation
  • ANSI Z535.4 – Product Safety Signs And Labels
  • 29 CFR 1910, Subpart S – OSHA Electrical Safety Standards

Why would you do field labeling?

Most cities require electrical field evaluations to protect the inhabitants of their city from disasters that can result from faulty electrical equipment (tools). They are enforcing the NEC (National Electric Code) that states: All “conductors of electricity” must be “approved,” “identified,” “listed” or “labeled”. The code allows for a capable third party (LBIES) to perform an electrical evaluation of your product.

A field evaluation satisfies local and/or state electrical and building inspector’s requirements.

A field evaluation protects your company, employees and building from potential catastrophes.

A field evaluation assures safer and more reliable products.

A field evaluation aids in defense of product liability action.

A field evaluation is cost effective.

A field evaluation gives the assurance that a product, process, or service conforms to all specified requirements.

A field evaluation provides an outside independent evaluation to ensure your money was well spent on your equipment.

What does the field label testing look for?

Risk of Fire


Properly sized components

Appropriate non-combustible enclosures

Over-current/Overload protection & sizing

Risk of Shock


Protection against accessibility

Appropriate enclosures

Articulated Finger Probe


Risk of Mechanical Hazards

Pinch points/sharp points/Tip Hazard

Accessibility to moving parts – Crushing and Tearing Hazards

Appropriate Enclosures/Guards

Appropriate warnings and labels

Risk of High Current/Energy


Manufacturer/Model No./Electrical Ratings

Caution markings

Risk of Fire/Shock/Mechanical Hazards

Caution markings relevant to hazards within the installation site

What is evaluated in field labeling?

To ensure the electrical safety integrity of the tool, field evaluations focus on a number of key areas of the tool’s construction.

The following summarizes the fundamental testing methods of a field evaluation:

Electrical Testing


Over-current Protection

Lockout/Tag out


EMO Tests

Other Hazards

Unique situations where field labeling is required

  1. Typically, tools that are NRTL listed do not need field evaluation services to be performed on them. But, if 2 or more NRTL-listed tools are joined to perform a special action, the NRTL listing is nullified and the tools must be field labeled.
  2. Tools that are custom built or one of a kind need a field evaluation.
  3. If an Authority Having Jurisdiction (AHJ/city inspector) says you need a UL or NRTL, they are saying you need a field label (see 1 and 2 above) and they can request these field evaluation services at their sole discretion.

Field labeling testing procedures

There are many sub-categories of testing that make up a full 3rd party field evaluation of an unlisted tool. When you request field evaluation services for an unlisted tool, please pay attention to the following list of sub-categories and their associated testing procedures. It is important to be acquainted with them so your team can determine if your tool(s) will meet all the codes ahead of a field evaluation being requested or performed at your facility.


Machine grounding is tested at numerous points on the equipment, including all exposed metal surfaces that enclose electrical components. Ground continuity testing is performed at 30 amps and is required to demonstrate ground resistance is less than 0.1 ohm at all points measured referenced to facility ground.

Surface leakage is tested to ensure that no more than 3.5mA of current exists on the exposed conductive surfaces of the equipment during non-fault operating conditions.

Input current is tested and the electrical design of the equipment evaluated to ensure the correct size of the main over-current device is employed. The electrical components and connections within the equipment are measured for acceptable heating to ensure that the electrical components are not operating at their stress levels during normal equipment operation.


Wiring methods are reviewed to ensure the requirements of NFPA 79 are met for conductor colors, incidental contact, segregation of control circuits and devices, ground conductors, labels, buttons, and indicators.

Isolation of hazardous voltages from earth ground as well as signal conductors are evaluated and tested through visual inspections and high potential breakdown testing to validate the visual inspection.

Lockout/Tag out

The equipment is examined to ensure that the facility feed conductors are provided with the correct clearances and termination points according to NFPA 70 and NFPA 79. The main disconnect handle and main LOTO provisions are examined for conformance to NFPA 70, NFPA 79, and OSHA requirements. The electrical enclosure(s) of the equipment is examined for suitability within the environment in which they are incorporated according to the conditions described in UL 508 and UL 50.

The full requirements of OSHA compliance for LOTO provisions on the hazardous energy on the equipment, as well as isolation for electrical energy are thoroughly reviewed. All of the energy that the facility provides to the equipment is examined and an evaluation of the ability to isolate all energy (process gasses, pneumatic gases, cooling water, process liquids, etc.) with lockable isolation features is done.


We identify all hazards on the system and review the equipment for Hazard Warning labels according to the potential hazards present on the equipment and ANSI Z535.4.

EMO Tests

Test the proper operation of any emergency stops for reliability and proper functioning.

Other Hazards

Special consideration is given to ground fault protection requirements on equipment that incorporates immersion heaters. Those systems that could create an unpredictable current path through liquid distribution lines are carefully evaluated to ensure that any faults in the heating system are mitigated before they become an electric shock hazard to personnel.

For equipment that uses flammable chemistry, the requirements to use electrical components that are listed for use in classified locations are examined in detail.

Where it is not possible to obtain components for classified locations, one of the requirements is that the equipment manufacturer has to produce the test reports that demonstrate adequate dilution of the flammable chemistry has been provided, and gives all pertinent information to conclude the evaluation.

Required compliance and safety testing

In addition to relevant construction evaluations, the tool will also be tested for compliance to safety requirements in the course of a field evaluation. The tests may vary depending on the type of tools being tested.

You can also learn more about what to expect during a field label evaluation from this blog here.

Some of the most common tests are:

Grounding Continuity Test:
Testing for proper grounding and bonding of the whole equipment.

Dielectric Voltage Withstand Test (Hi Pot Test):
Testing for adequate spacing between conductive parts. The test is performed between primary and ground and primary and secondary of the unit.

Input Current Test:
Measuring the input current of the unit during maximum load operation and evaluating the suitability of protection mechanisms such as fuses, circuit breakers, etc.

Strain Relief Test:
Measuring the strength and suitability of strain relief through push and pull tests.

Interlock Test:
Tests the suitability and performance of all interlocks giving access to live parts and moving components.

What if a tool is found to be non-compliant?

For situations where non-compliances are found on the tool(s) covering the following line items listed below, a punchlist will be generated showing clear pathways for addressing the non-compliances.

Your staff and electrical contractors will need to work together to address these non-compliances so that a second field evaluation visit will allow for a successful field labeling and passing report.

Typical punchlist items cover the following potential line items covered in our field evaluation:

Electrical testing – our testing results do not accurately confirm the tool’s nameplate data.

Wiring – the type, size, or color is not suitable/wrong or unsafe.

Over-Current Protection – the fuses or breakers for the tool are not suitable for the load.

Lockout/Tagout – the tool is missing a LOTO program (if applicable).

Labeling – the tool is missing required warning or hazard labels.

EMO Tests – EMO (Emergency Off Button) button may not be functioning when pressed, turn off the entire system it is connected to, or could be of an incorrect design type.

Fixing punchlist items:

Lewis Bass, as an FEB (Field Evaluation Body) per NFPA 790, can not directly provide guidance and next steps for fixing non-compliances in your equipment. We can, however, direct you toward companies that do this type of work but whom have no connection to us.

Punchlist items must be address promptly to close a building permit.

Lewis Bass project managers will periodically reach out to you and your staff to see if the identified punchlist items have been addressed. Once these fixes have been completed, a second facility visit will be scheduled so that our field technician can verify the fixes have been appropriately addressed and that the equipment is now compliant. Once confirmed, the field technician will attach a Lewis Bass Field Label and issue a Final Report for you and the AHJ requesting the field evaluation.

Field labeling resources

Are you interested in self-identifying your unlisted equipment in your facility? If so, click here to download the Lewis Bass, “How to Identify Unlisted Equipment” flyer!

Are you a General Contractor working on job sites where unlisted equipment needs to be installed and you want to partner with Lewis Bass to offer our services at your markup? Please click here for our flyer detailing our referral structure and how to offer these services to your clients.

Our FLE Label

The above mockup is an example of what our Field Label looks like and what information is generally displayed for an inspector’s review. Our labels in the field are made of durable metal material.

For an example City (AHJ) list of approved 3rd party electrical testing laboratories that also shows how companies like Lewis Bass are vetted to perform our work in these jurisdictions, click here.

Learn more about field labeling from our blog:

Ready for a quote for field label services?

In a rush? Call or text us now at (408) 942-8000 for expedited service.