ATPV and EBT are the two values used to express an arc rating. ATPV shows the heat level that may cause a second-degree burn. EBT shows the heat level that makes a fabric break open. Knowing the ATPV rating helps you choose safer arc-rated clothing for electrical work.
This guide explains each term in plain English. It also shows how to match the arc rating of clothing to your task.
What Is an Arc Rating, and How Does the ATPV Rating Fit In?
An arc rating shows how much heat energy a fabric can handle during an arc flash. The ATPV rating is one way to express it.
The arc rating definition is simple. It is the tested level of protection that a material gives against an electric arc. The arc rating meaning is just as clear. A higher number means the fabric can handle more heat energy.
Arc ratings are expressed in calories per square centimeter (cal/cm²). Arc ratings are expressed as either ATPV or EBT, depending on the test result. The arc rating ATPV value on a label tells you how much heat the fabric can take.
What Does ATPV Mean, and What Is an ATPV Rating?
ATPV stands for Arc Thermal Performance Value. The ATPV rating is the heat energy that gives a 50 percent chance of a second-degree burn under the fabric.
That is the full ATPV meaning in one line. Testers measure the heat that passes through the fabric to a sensor. They then compare it with a standard skin burn curve.
Key points about ATPV:
- It is measured in cal/cm².
- It applies when the fabric stays intact during the test.
- It appears on the garment label.
- A higher ATPV rating means more protection from heat.
Because of this, the ATPV rating is the main number buyers look for on arc-rated clothing.
What Is EBT, and How Does It Differ from the ATPV Rating?
EBT stands for Energy Breakopen Threshold. It is the heat energy at which a fabric has a 50 percent chance of breaking open during an arc test.
A breakopen creates a hole, so hot gases can reach the skin. For that reason, labs report EBT when the fabric breaks open before it reaches the ATPV level.
|
Feature |
ATPV |
EBT |
|
Full name |
Arc Thermal Performance Value |
Energy Breakopen Threshold |
|
What it measures |
Heat that may cause a second-degree burn |
Heat that makes the fabric break open |
|
Unit |
cal/cm² |
cal/cm² |
|
When it is reported |
Fabric stays intact |
Fabric breaks open first |
|
Label use |
Counts as the arc rating |
Counts as the arc rating |
Both values carry equal weight. Treat each one as the garment's arc rating.
How Is an ATPV Rating Derived Under NFPA 70E?
Labs derive an ATPV rating by exposing fabric to a controlled electric arc under the ASTM F1959 test. NFPA 70E then uses that result for PPE selection.
So how is arc rating derived under NFPA 70E? The process has three steps:
- Sensors sit behind a fabric panel.
- An electric arc strikes the panel at set energy levels.
- Labs record the heat that passes through, or the point where the fabric breaks open.
The lab then reports the correct value as the arc rating. NFPA 70E defines arc rating as either ATPV or EBT. It does not rank one above the other.
Which ATPV Rating Do You Need for Your Job?
You need an ATPV rating equal to or higher than the incident energy at your task. Your arc flash risk assessment gives you that number.
A higher number is not always better. Heavier fabric often feels hotter and limits movement. Workers may then open or remove it. Therefore, pick the right rating first, and then choose the most comfortable fabric that meets it.
Common mistakes to avoid:
- Buying by price or weight alone.
- Ignoring the garment label.
- Wearing melting underlayers beneath arc-rated clothing.
- Forgetting that layered outfits carry their own system rating.
Always check the arc rating of clothing before you buy. The label should show the standard, the cal/cm² value, and the care instructions. Teams that need help matching garments to tasks can review the range at nkesafetyapparel.
This ATPV rating chart shows the NFPA 70E minimum arc rating for each PPE category:
|
PPE Category |
Minimum Arc Rating |
Where You May See It |
|
1 |
4 cal/cm² |
Low-energy panel work |
|
2 |
8 cal/cm² |
Common panel and motor control tasks |
|
3 |
25 cal/cm² |
Higher-energy switchgear work |
|
4 |
40 cal/cm² |
Very high-energy equipment |
What Is a CAT 2 Arc Rating, and How Does It Relate to the ATPV Rating?
A CAT 2 arc rating refers to PPE Category 2, which requires clothing rated at least 8 cal/cm². It is a minimum, not a fixed value.
A PPE category and an ATPV rating are different things. The category is a level in NFPA 70E. The ATPV rating is a test result for the fabric. For example, a shirt with an 11 cal/cm² ATPV rating meets Category 2 because 11 is higher than 8.
Do not confuse these terms with an arc fault rating. That term describes electrical equipment, such as switchgear, and not clothing.
What Do People Ask About the ATPV Rating?
1. What does ATPV stand for?
ATPV stands for Arc Thermal Performance Value.
2. What is the difference between ATPV and EBT?
ATPV relates to burn risk, while EBT relates to fabric breakopen.
3. What does an arc rating mean?
It shows the heat energy, in cal/cm², that a fabric can handle during an arc flash.
4. What is a good ATPV rating?
A good ATPV rating meets or exceeds the incident energy of your task.
5. Is ATPV the same as arc rating?
No. ATPV is one way to express an arc rating, and EBT is the other.
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