UL 121201 vs. UL 698A: Which Standard Applies to Your Industrial Control Panel?

07 Sep 2026

How Understanding the Distinction Between the Two Standards Helps Determine Which Should be Applied

When a control panel includes a device that provides a protected, low-energy output to field wiring in a hazardous location, should the panel be evaluated to UL 121201 or UL 698A?

Understanding the distinction between these two standards early in a project can help avoid redesigns, certification delays, and unnecessary costs.

Start by Identifying the Purpose of Each Standard

UL 121201 – Industrial Control Panels with Associated Nonincendive* Field Wiring

UL 121201 evaluates industrial control panels intended to be installed directly in a hazardous location. The standard focuses on ensuring that the equipment does not become an ignition source under the applicable operating conditions and hazardous-location classification.

For industrial control panels, this generally means:

• The panel enclosure is installed in a Class I, Division 2; Class II, Division 2; or Class III, Division 1 or Division 2 location, as applicable.
• Components are selected and evaluated for use in the intended hazardous environment.
• The panel may include associated nonincendive field wiring apparatus that provides protected, low-energy outputs to the inputs of nonincendive field wiring apparatus.
• The design addresses potential ignition sources, including arcs, sparks, and excessive surface temperatures.

In simple terms, UL 121201 addresses panels intended for installation in the hazardous location that incorporate associated nonincendive field wiring apparatus and nonincendive field wiring apparatus as part of the field wiring circuit.

UL 698A – Industrial Control Panels with Intrinsically Safe** Circuit Extensions

UL 698A serves a different purpose. It applies to industrial control panels located in a non-hazardous area that provide intrinsically safe circuit extensions to intrinsically safe devices located in hazardous areas.

• These hazardous areas may include Class I, Class II, or Class III, Division 1 locations, as well as applicable Zone 0, Zone 1, Zone 20, or Zone 21 locations.
• Intrinsic safety is a protection technique that limits the electrical and thermal energy available in a circuit so that it cannot ignite the surrounding hazardous atmosphere, including under specified fault conditions.

In this case, the panel itself is not necessarily hazardous-location equipment. Instead, the panel provides intrinsically safe circuits that safely interface with equipment installed in the hazardous area.

Although both standards involve low-energy field circuits, they use different protection concepts and terminology.

Real-World Examples

Example 1: Remote Pump Station

A control panel is mounted outdoors at a natural gas wellhead classified as Class I, Division 2. The panel includes a device that provides a protected, low-energy output to a field device also located in the Class I, Division 2 area.

Because the panel itself is installed in the hazardous location and the application uses associated nonincendive field wiring, UL 121201 would be the standard to consider.

Example 2: Control Room

A PLC panel is installed in an air-conditioned control room outside the classified area.

The panel contains intrinsic safety barriers or associated apparatus that provide intrinsically safe circuit extensions to pressure transmitters located in a Class II, Division 1 hazardous area.

In this case, UL 698A would generally be the applicable panel standard because the panel is located in a non-hazardous area and provides intrinsically safe circuit extensions to hazardous-location equipment.

Example 3: Combination Application

Consider a panel installed in a Division 2 hazardous location that also contains intrinsic safety barriers providing intrinsically safe circuit extensions to field instruments located in a Division 1 area.

In this situation, both standards may need to be considered:

• UL 121201 addresses the suitability of the panel for installation in the Division 2 hazardous location.
• UL 698A addresses the intrinsically safe circuit extensions incorporated into the panel.

Final Thoughts

UL 121201 and UL 698A are not competing standards – they address different hazardous-location applications and different field wiring protection concepts.

When determining which standard may apply to your control panel, start with two questions:

1. Where is the panel installed?
2. What type of protected field wiring circuit is being provided?

If the panel is installed in a hazardous location and incorporates associated nonincendive field wiring apparatus and nonincendive field wiring apparatus, UL 121201 may be the appropriate standard to consider.

If the panel is installed in a non-hazardous location and provides intrinsically safe circuit extensions to hazardous-location devices, UL 698A may be the appropriate standard.

Identifying these differences early in the design process can help engineers, panel builders, and end users select the appropriate certification path, reduce design changes, and streamline the overall certification process.

 

*Nonincendive refers to electrical circuitry, components, equipment, or field wiring that, under specified normal operating conditions, is not capable of producing an arc, spark, or thermal effect with sufficient energy to ignite a specified flammable atmosphere.

**Intrinsically Safe refers to refers to electrical circuitry, components, equipment, or field wiring that, the electrical energy in a circuit is limited such that any spark or thermal effect produced during normal operation or under specified fault conditions is incapable of igniting the specified flammable or combustible atmosphere.