UL94 Flame Ratings Explained: 94V-0 vs 94V-2 and How to Spec

UL94 Flame Ratings Explained: 94V-0 vs 94V-2 and How to Specify Correctly

A specification says "UL94 V-0", but the bill of materials lists a 94V-2 cable tie. The two ratings look close, so can one replace the other? No. Each UL94 class is a separate threshold, and the classes are not interchangeable. This article explains the four classes and matches them to real parts in the KSS catalog, so you know exactly which series to name in your specification.

Title: Laboratory vertical burn test measuring the self-extinguishing behavior of a plastic specimen - Description: Laboratory vertical burn test measuring the self-extinguishing behavior of a plastic specimen

1. What UL94 Measures: A Grading of Self-Extinguishing Ability

UL94 is a flammability test standard for plastic materials. It asks one practical question: once the material is ignited, can it put itself out? The classes rise in this order: HB, V2, V1, V0, with V0 the highest. HB uses a horizontal burn test. V2, V1 and V0 use a vertical burn test, which is more demanding. The KSS catalog marks each part with a flame rating symbol system (P.254).

Class	Test method	What it checks (summary)	KSS catalog examples
HB	Horizontal burn	Lowest threshold of the four	CV-N612 (Nylon 612, HB, P.68); CV-CWBK (94HB, P.70)
V2	Vertical burn	Must self-extinguish within a set time after the flame is removed; burning drips may ignite cotton below	Mainstream CV / CVT, CV-W, CV-HS, CV-N46 (94V-2)
V1	Vertical burn	Same type of self-extinguishing limit as V2, but drips must not ignite cotton	No 94V-1 part appears in the catalog data used for this article
V0	Vertical burn	Shortest self-extinguishing time; drips must not ignite cotton; the highest class	CV-V0 (P.69); MHF-4040 (P.24); CE-1V0 to CE-8V0 closed-end terminals

The "what it checks" column is a summary. Exact times and test conditions are defined in the UL94 standard and in each material's UL certification file.

Title: UL94 plastic flammability classifications progress from HB through V-2 and V-1 to V-0 - Description: UL94 plastic flammability classifications progress from HB through V-2 and V-1 to V-0

2. 94V-0 vs 94V-2: Two Different Thresholds

Placing V2 next to V0, the difference comes down to two points. First, V0 allows a shorter self-extinguishing time after the flame is removed. Second, V2 allows burning drips to ignite the cotton below, while V0 does not. In the field this means a practical question: if other cables or equipment sit beneath a bundle, could falling molten material start a second fire? In the KSS catalog the two ratings belong to different series:

Product	Series / model	Material and flame rating	Catalog page
Standard cable tie	CV / CVT	UL-recognized Nylon 66 / 94V-2	P.64-65
UV-resistant cable tie	CV-W	UL-recognized Nylon 66, UV-stabilized / 94V-2	P.72-73
Heat-stabilized cable tie	CV-HS	UL-recognized Nylon 66 / 94V-2	P.68
High-temperature cable tie	CV-N46	UL-recognized Nylon 46 / 94V-2, up to 150°C	P.67
Flame-retardant cable tie	CV-V0	UL-recognized Nylon 66 / 94V-0, length 100 to 380 mm, tensile strength 18 to 120 lbs	P.69
Weather-resistant cable tie	CV-N612	UL-recognized Nylon 612 / HB	P.68
Closed-end terminal	CE-1 to CE-8 / CE-1V0 to CE-8V0	Copper barrel with UL-recognized Nylon 66; standard version 94V-2, flame-retardant version 94V-0	—
Halogen-free wiring duct	MHF-4040	UL-recognized white PC/ABS / 94V-0, rated to 100°C	P.24

Title: CV and CVT cable ties rated 94V-2 and CV-V0 cable ties rated 94V-0 address different requirements and are not interchangeable - Description: CV and CVT cable ties rated 94V-2 and CV-V0 cable ties rated 94V-0 address different requirements and are not interchangeable

3. Three Common Mistakes

Mistake 1: "94V-2 means fire safety is covered."

94V-2, 94V-0 and 94HB are different classes and cannot be substituted for one another. The mainstream KSS CV series is 94V-2. If the drawing or specification requires 94V-0, you must name the CV-V0 series; a standard CV part is not an acceptable replacement.

Mistake 2: "94V-0 means halogen-free."

Halogen-free (IEC 61249-2-21) describes what a material releases when it burns. UL94 describes whether it burns and whether it can put itself out. These are two separate requirements, and a 94V-0 material can still contain halogens. In the KSS catalog, MHF-4040 is the example that carries both marks, and it is currently the only size listed in that series. For cable ties, the current catalog does not show a part number marked halogen-free, so please confirm with our sales team if your specification requires it.

Mistake 3: "A higher class is always better, so choose V0 everywhere."

Flame rating is only one field in the selection. Operating temperature, UV resistance, tensile strength and certification coverage matter as well. For example, for long-term outdoor sun exposure the UV-resistant CV-W is the series that addresses the problem. Naming the series that fits the environment is more practical than raising the class everywhere.

Title: 94V-0 and halogen-free are separate requirements; MHF-4040 combines halogen-free material with a 94V-0 rating - Description: 94V-0 and halogen-free are separate requirements; MHF-4040 combines halogen-free material with a 94V-0 rating

4. Selection Guide: Work Backwards from the Specification

• No flame rating specified: for general in-panel and machine wiring, the mainstream CV series (94V-2) applies.

• Fire compartment, or the specification explicitly lists 94V-0: name CV-V0 (P.69) and write the series name on the bill of materials, not just "nylon cable tie".

• Inside a cabinet, with both halogen-free and 94V-0 required: MHF-4040 (P.24), where both marks appear on the same part number.

• Outdoor, corrosive or cold environments: choose the series for the environment first, then confirm the flame rating of that series if a fire requirement applies.

Contact

For the full part number list and specifications by flame rating, please contact:

Jwo Yiih Enterprise CO., LTD.

Note: part numbers, materials, flame ratings and page numbers in this article are taken from the KSS factory catalog (page numbers are printed catalog pages; the flame rating symbol system is on P.254) and from previously verified industry product lists and the Week 1, 2, 4 and 5 articles. The UL94 class descriptions are summaries of the standard. Certification and flame rating vary by specific model and SKU. For a formal quotation, please confirm current part numbers with our sales team.

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