When selecting flame-resistant (FR) clothing for electrical work, two critical terms dominate the conversation: ATPV (Arc Thermal Performance Value) and EBT (Energy Breakopen Threshold). Both measure a fabric’s ability to protect against arc flash hazards—but in different ways.
Understanding these ratings ensures you choose the right level of protection for your team. In this guide, we’ll break down:
✔ What ATPV and EBT mean
✔ How they’re tested
✔ Which rating matters most for your industry
✔ Common misconceptions debunked
1. What Is ATPV? (Arc Thermal Performance Value)
ATPV measures how much thermal energy (in calories/cm²) a fabric can block before the wearer has a 50% chance of second-degree burns.
Key Facts About ATPV:
- Tested via ASTM F1959: A controlled arc simulates real-world electrical faults.
- Higher ATPV = Greater Protection:
- ATPV 4 cal/cm² → Low-risk tasks (HRC 1)
- ATPV 8+ cal/cm² → High-voltage electrical work (HRC 2-4)
- Limitation: ATPV doesn’t predict whether the fabric will break open during an arc flash.
2. What Is EBT? (Energy Breakopen Threshold)
EBT measures the minimum energy required to cause the fabric to split or rupture during an arc flash, exposing the wearer to direct heat.
Key Facts About EBT:
- Tested alongside ATPV in the same ASTM F1959 test.
- Lower EBT = Higher Risk: If a fabric’s EBT is lower than its ATPV, the material may fail structurally before burn protection is compromised.
- Critical for High-Energy Environments: Industries like utility linemen prioritize EBT to prevent catastrophic fabric failure.
3. ATPV vs. EBT: Which Matters More?
| Factor | ATPV | EBT |
|---|---|---|
| Measures | Heat transfer (burn risk) | Fabric integrity (tearing risk) |
| Ideal For | General FR protection | High-energy arc flash zones |
| Priority | Most FR clothing labels show ATPV | Critical for HRC 3-4 (utilities) |
Example:
- A 12 cal/cm² ATPV FR shirt with an 8 cal/cm² EBT means the fabric could rip open at 8 cal/cm²—even though it blocks heat up to 12 cal/cm².
4. How to Choose Based on Hazard Risk Category (HRC)
The NFPA 70E standard classifies arc flash risks into HRC 1-4:
| HRC | Incident Energy (cal/cm²) | Required ATPV/EBT | Typical Applications |
|---|---|---|---|
| 1 | Up to 4 | ATPV 4+ | Low-voltage panel work |
| 2 | Up to 8 | ATPV 8+ | Electricians, facility maintenance |
| 3 | Up to 25 | ATPV 25+ + High EBT | Utility linemen, substations |
| 4 | Up to 40 | ATPV 40+ + Critical EBT | High-voltage transmission work |
Pro Tip: For HRC 3-4, look for EBT ≥ ATPV to ensure the fabric won’t tear before reaching its rated protection.
5. How Firebear Ensures Optimal ATPV & EBT
Our inherent FR fabrics (modacrylic/aramid blends) are engineered to:
✔ Resist breakopen even after repeated washes.
✔ Pass third-party ASTM F1959 testing with full reports available.
Choosing FR clothing isn’t just about ATPV—EBT is equally critical for high-risk electrical work. Always:
- Match ratings to your HRC level.
- Prioritize EBT for utilities and high-voltage tasks.
- Demand test reports (don’t rely on marketing claims).