UL 94 Flammability – UL 94

What Is UL 94 Flammability?

UL 94 is a flammability test that classifies the response to flame of plastic materials used in devices and components. Horizontal burning (HB), vertical burning (V classes) and the more severe 5V tests are defined according to the specimen's orientation and the manner of flame application.

Purpose of UL 94 Flammability

The purpose is to determine whether a plastic material self-extinguishes after ignition and whether it produces flaming drips. Electrical-appliance standards require a minimum UL 94 class according to where the material will be used.

Which Products Is UL 94 Flammability Applied To?

Electrical-appliance enclosures
Printed-circuit-board carriers and connectors
Switch, socket and enclosure housings
White-goods internal components
Luminaire housings

In Which Sectors Is UL 94 Flammability Used?

PlasticsElectronicsElectricalConsumer ProductsAutomotive

Standards Related to UL 94 Flammability

UL 94flammability class in plastic materials test

UL 94 Flammability Conditions

Classes: HB, V-2, V-1, V-0, 5VB, 5VA — the class is determined by the test result
Specimen orientation: Horizontal (HB) or vertical (V and 5V classes)
Conditioning: Defined in the standard; an aged specimen set is also tested
Thickness: The class is valid at a specific thickness; if the thickness changes, the class is re-determined

Equipment for UL 94 Flammability

UL 94 burn chamber and gas burner
Specimen-holder rigs
Stopwatch and cotton-pad rig
Conditioning room and ageing oven
Ventilation and gas-extraction system

Sample Requirements for UL 94 Flammability

Bar or sheet specimens of the dimensions defined in the standard are required
A separate specimen set must be prepared for each class and thickness
The material's colour and filler content affect the result; each variant must be tested separately
The material identification, manufacturer and, if any, flame-retardant information must be shared
The test is destructive

Duration of UL 94 Flammability

The test itself is short, but the conditioning and ageing periods determine the total; the result generally comes out within a few working days.

UL 94 Flammability Procedure

1Specimens are prepared to the dimensions defined in the standard.
2Specimen sets are conditioned; one set is additionally aged.
3The specimen is placed in the test orientation.
4The flame is applied for the defined time and withdrawn.
5The flaming time is measured; a second flame application is made.
6The afterglow time, dripping and whether the cotton pad ignites are recorded.
7A class is assigned by comparing all specimen results against the class criteria.

UL 94 Flammability Acceptance Criteria

Class criteria are defined in UL 94's own text: the total flaming time, the single-specimen time, burning up to the holder, and the production of flaming drips are evaluated together. If even one specimen exceeds the criterion, that class is not assigned.

Evaluation of Results

The class depends on both the material AND THE THICKNESS together; a material achieving V-0 at 1.5 mm may not achieve the same class at 0.75 mm. Colour pigment and filler changes also affect the class, which is why each variant is tested separately.

UL 94 Flammability Report

Sample description, serial number and configuration
Applied standard and year of printing
Selected intensity level and basis for the level
Experimental setup and measurement points
Functional checks performed during the experiment
Observations, measurement results and photographs
A statement that the result applies only to the specimen submitted for testing

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

Product standards under EU 2014/35/EU LVD
IEC 60335 series (household and similar electrical appliances)
IEC 62368-1 (audio/video and information-technology equipment)

Standard-Based Tests — What Does This Group of Pages Cover?

The section below describes the field that the UL 94 Flammability test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Standard-based tests are test pages whose address comes from a standard number. What the user is looking for is often not the name of the test but the code written in their specification: not "salt spray test" but "ASTM B117", not "drop test" but "IEC 60068-2-31", not "vibration" but "MIL-STD-810 Method 514".

This preference reflects the reality in the field. An engineer sees a code in the specification received from a customer and searches for that code; they do not need to know the name of the test. The code is the identity of the test and distinguishes the different adoptions of the same test by different bodies.

This group addresses the different adoptions of the SAME TEST separately. The same physical phenomenon may be published under different numbers by ISO, ASTM, EN, IEC, DIN and JIS. Even where the numbers are the same (as with ISO 6892-1 and EN ISO 6892-1), specimen preparation, conditions, calculation details and reporting may differ; adoptions may carry national annexes. The code written in the specification therefore governs, and "similar" is not accepted.

Searching at code level meets a different need from searching at scope level. A user searching for "corrosion testing" wants to learn about the field; a user searching for "ASTM B117" has a specification in hand and wants to know the feasibility, duration and price of that test. Two different intents require two different page structures.

The page for a code describes the scope of that code, the test field it belongs to, the product groups in which it is required and how it differs from neighbouring codes. Test conditions, durations and acceptance criteria are NOT CARRIED: these are defined in the copyrighted text of the standard and in the product specification. This boundary is a deliberate choice; a wrong duration or acceptance criterion means directly incorrect work.

Different parts of the same code and different adoptions of the same number are linked between pages. A user searching for IEC 60335 also sees 60335-2-40; a user searching for ISO 6892-1 also sees the EN ISO 6892-1 and DIN EN ISO 6892-1 adoptions. These links are derived from the number of the code rather than written by hand.

The edition year is NOT CARRIED in the library. It is held as "ASTM D638" rather than "ASTM D638-22", because the edition in force changes over time and the address of the page should not age with the edition. If a year is stated in your specification, that edition governs; if not, the most current edition is applied.

Method groups in this field

Searching by code
Direct search for the code written in the specification; it is found in the library with its code, scope title and issuing body.
Searching by scope title
A test whose code is not known is searched by its subject; a search for "salt spray" brings up the related codes.
Series and part relationships
The other parts of the same series are shown, derived from the number of the code.
Adoption relationships
Different bodies' adoptions of the same number are matched; the claim is kept limited to "the same number".
Superseded codes
Withdrawn codes are not held in the library but, when searched for, the user is directed to the counterpart in force.

Commonly confused in this field

Different adoptions of the same number are not identical texts; they may carry national annexes.
The code written in the specification governs; a technically similar code cannot be substituted.
If an edition year is stated, that edition is applied; the most current edition is not automatically accepted.
A code page carries no test conditions or acceptance criteria; these are in the copyrighted text of the standard and in the product specification.
A part code (for example -2-40) may not be sufficient on its own; the general part of the series is applied as well.

Which decisions these results support

Matching the code written in the specification to the correct laboratory scope
Distinguishing between equivalent adoptions
Clarifying the scope and edition at the quotation stage
Finding the current counterpart of withdrawn codes

Related Tests

Frequently Asked Questions About UL 94 Flammability

Is V-0 always better than V-1?

Among the V classes, V-0 is the strictest. However, the 5VA/5VB tests use a more severe flame source; these are a separate category above the V classes.

If the material is certified, is the product also certified?

No. The material class is an input piece of information. The product's own standard determines which class that part must meet, and the product is evaluated separately.