UL94 Flammability Standards: Vertical & Horizontal Burn
UL94 test is a preliminary sign to check the flammability of plastics used in any application. For example, plastic parts used in electronic devices and appliances.
UL94 class：HB、V-0、V-1、V-2、5VA、5VB、VTM-0、VTM-1、VTM-2、HBF、HF-1、HF-2。
HB is horizontal burn
V0，V1，V2，5VA，5VB are vertical burn；
VTM-0，VTM-1，VTM-2 are vertical burn for film materials；
HBF，HF-1，HF-2 is horizontal burn for foamed plastic.
1. Horizontal burn：HB
Test method
Flammability rating UL 94 HB
|
Test criteria |
Burning rate in V |
Flammability rating |
|
Test specimen thickness 3-13mm |
≤40 mm/min |
HB |
|
Test specimen thickness < 3 |
≤75 mm/min |
HB |
|
Flame is extinguished before first mark |
≡ 0 mm/min |
HB |
2. 50w（20mm）Vertical test（UL 94-V）:V-0、V-1或V-2
Test method
Flammability rating UL 94 V
|
Test Criteria |
V-0 |
V-1 |
V-2 |
|
Burning time of each individual test specimen (s) |
≤10 |
≤30 |
≤30 |
|
Total burning time (s) |
≤50 |
≤250 |
≤250 |
|
Burning and afterglow times after second flame application (s) |
≤30 |
≤60 |
≤60 |
|
Dripping of burning specimens |
no |
no |
yes |
|
Combustion up to holding clamp |
no |
no |
no |
3. 500w（125mm）Vertical test 5VA or 5VB
Test method
Rod test
Sheet test
Flammability rating UL 94 5VA 5VB
|
Test critieria |
5VA |
5VB |
| Burning and afterglow times of specimens after fifth flame application (s) |
60s |
60s |
|
Dripping of burning specimens |
No |
No |
| Hole formation |
No |
Yes |
4. UL 94 VTM Rating: VTM-0, VTM-1 and VTM-2 ‐ Thin Material Vertical Burning Testing
Flammability rating UL 94 VTM
|
Test Criteria |
VTM-0 |
VTM-1 |
VTM-2 |
|
Burning time of each individual test specimen (s) |
10s |
30s |
30s |
| Total burning time (s) (10 flame applications) |
50s |
250s |
250s |
| Burning and afterglow times after second flame application (s) |
30s |
60S
|
60s |
| Dripping of burning specimens (ignition of cotton batting) |
No |
No |
Yes |
| Combustion up to holding clamp (specimens completely burned) |
No |
No |
No |
5. UL 94 HBF: HBF, HF-1 and HF-2 ‐ Horizontal Burning Foamed Material
Flammability rating UL 94 HBF, HF-1, HF-2
This test grants three different types of ratings depending on burning rates and or after flame times. A material will be classified as an HBF material:
if it does not have a burning rate exceeding 40 mm per minute over a 100 mm span or
if it ceases to burn before flaming or glowing reaches the 125 mm mark.
|
Test criteria (test specimens) |
HF-1 |
HF-2 |
| Burning time (s) |
4/5 2s 1/5 10s |
4/5 2s 1/5 10s |
|
Burning and afterglow time of each individual specimen (s) |
30s |
30s |
|
Dripping of burning specimen (ignition of cotton batting) |
No |
No |
|
Damaged length of individual specimen (mm) |
<60 mm |
<60 mm |
