Learn · Glossary
What Does UL94 V-0 Mean? Flammability Ratings Explained
What is UL 94?
UL 94 is a widely used standard from UL (originally Underwriters Laboratories) for the flammability of plastic materials used in parts of devices and appliances. It describes how a small sample of plastic behaves when exposed to a flame: whether it keeps burning, how quickly it stops, and whether it drips burning particles that could spread a fire.
You’ll often see a UL 94 rating required for electrical and electronic enclosures, appliance parts, connectors and housings near power sources.
The UL 94 ratings, from least to most demanding
| Rating | Test | What it means |
|---|---|---|
| HB | Horizontal burn | Burns slowly on a horizontal sample, within a set rate. The least demanding rating. |
| V-2 | Vertical burn | Stops burning within 30 seconds; flaming drips are allowed. |
| V-1 | Vertical burn | Stops burning within 30 seconds; no flaming drips that ignite cotton below. |
| V-0 | Vertical burn | Stops burning within 10 seconds; no flaming drips that ignite cotton below. |
| 5VB / 5VA | Vertical burn with a larger flame, applied five times | The most demanding ratings. 5VA also requires that test plaques don’t burn through. |
How the vertical (V) test works
A bar of the material is held vertically, with a layer of cotton beneath it. A small flame is applied to the bottom of the bar for 10 seconds and removed, then applied for another 10 seconds. The test records how long the sample keeps burning after each application, whether it glows, and whether burning drips ignite the cotton. Several samples are tested, and all must pass for the rating.
UL 94 is not the same as…
- Heat resistance. A material can resist burning but still soften at moderate temperatures, and vice versa. See heat-resistant 3D printing materials.
- Aerospace FST requirements. Aircraft interiors use separate flame, smoke and toxicity (FST) tests, such as FAR 25.853. ULTEM™ 9085, for example, is FAA-approved for FST applications and meets FAR 25.853 and OSU 65/65.
Choosing a flame-retardant 3D printing material
- Check what your product needs. Find the rating your product standard or customer requires, and at what thickness.
- Read the datasheet. Confirm the material’s UL 94 rating and the thickness it was tested at.
- Design to that thickness. Keep walls at or above the tested thickness where the rating matters.
- Remember the whole product. The rating applies to the material; your final product may still need its own testing or certification.
Quick 3D offers flame-retardant materials including Formlabs Flame Retardant Resin for SLA and ULTEM™ 9085 for FDM, with full technical and safety data sheets. See our aerospace-grade materials.
*The ULTEM™ and 9085 trademarks are used under license from SABIC, its affiliates or subsidiaries.
Frequently asked questions
What does UL94 V-0 mean?
It means a plastic material stopped burning within 10 seconds after a flame was removed in the UL 94 vertical burn test, without dripping flaming particles that ignite cotton below. It is the highest of the V-0, V-1 and V-2 ratings.
Is V-0 better than V-2?
Yes. V-0 requires burning to stop within 10 seconds with no flaming drips. V-2 allows up to 30 seconds and permits flaming drips.
Is 5VA higher than V-0?
Yes. The 5VA and 5VB ratings use a larger flame applied five times and are more demanding than V-0.
Does a UL94 V-0 material make my product certified?
Not by itself. The rating applies to the material at a tested thickness. Your finished product may need its own testing or certification under the relevant product standard.
Need a flame-retardant part?
Tell us the rating and thickness you need. We’ll recommend a suitable material and process, with datasheets.
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