How To Read An Fr Coverall's Atpv/ebt Rating

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Selecting the right flame-resistant (FR) coveralls involves much more than choosing the correct size or fabric. One of the most important factors to understand is the garment's arc rating, commonly expressed as an ATPV or EBT value. These ratings provide critical information about the level of thermal protection an FR garment offers when exposed to an electric arc.
For safety managers, procurement teams, and workers who wear FR clothing in electrical or industrial environments, understanding ATPV and EBT ratings helps ensure the right protective clothing is selected for the hazards present. While these values may seem technical at first, they are based on standardized testing and offer a practical way to compare the protective performance of different FR coveralls.
This guide explains what ATPV and EBT ratings mean, how they are determined, and how to interpret them when choosing FR coveralls.
What Is an Arc Rating?
An arc rating is a numerical value that indicates how much incident thermal energy a flame-resistant garment can withstand before there ...
... is a 50% probability of causing a second-degree skin burn under laboratory test conditions.
Arc ratings are expressed in calories per square centimetre (cal/cm²), which measures the amount of thermal energy transferred to the fabric during an arc flash event.
Every FR garment intended for arc flash protection should display its arc rating on the product label or technical documentation. This allows employers to compare garments and select clothing that matches the level of protection required by their workplace hazard assessment.
The arc rating shown on an FR coverall will be reported as either an ATPV or an EBT value, depending on which threshold is reached first during testing.
Understanding ATPV
ATPV stands for Arc Thermal Performance Value.
It represents the amount of incident energy at which there is a 50% probability that sufficient heat will pass through the fabric to cause the onset of a second-degree burn.
In simple terms, ATPV measures how effectively the fabric insulates the wearer from thermal energy generated during an arc flash.
For example, if an FR coverall has an ATPV of 12 cal/cm², it means the garment was tested to withstand up to 12 calories of incident energy per square centimetre before reaching the burn prediction threshold under the specified laboratory conditions.
A higher ATPV generally indicates greater thermal insulation against arc flash exposure.
Understanding EBT
EBT stands for Energy Breakopen Threshold.
Unlike ATPV, EBT is determined when the fabric physically breaks open before enough heat passes through it to reach the burn prediction threshold.
During testing, some materials maintain excellent thermal insulation but may tear, split, or develop openings under intense arc exposure. Once the fabric breaks open, the wearer could be directly exposed to hot gases and molten materials, making the structural integrity of the garment the limiting factor.
When this occurs, the arc rating is reported as the EBT value instead of ATPV.
An EBT of 8 cal/cm², for example, means the fabric reached its breakopen threshold at that energy level before the thermal insulation limit was reached.
ATPV vs. EBT: What Is the Difference?
Although ATPV and EBT measure different performance characteristics, both are valid arc ratings.
The key difference lies in what causes the test to end.

ATPV measures the thermal energy level that predicts a second-degree burn without the fabric breaking open.
EBT measures the thermal energy level at which the fabric breaks open before reaching the predicted burn threshold.

The lower of these two values becomes the garment's official arc rating.
This means an FR coverall will display either an ATPV or an EBT value—not both as its certified arc rating—even though both characteristics are evaluated during testing.
How ATPV and EBT Ratings Are Determined
Arc ratings are established through standardized laboratory testing using methods such as ASTM F1959/F1959M, which evaluates the arc performance of flame-resistant materials under controlled conditions.
During the test, fabric samples are exposed to electric arc energy of increasing intensity while specialized sensors measure the amount of heat transferred through the material.
Researchers evaluate two possible outcomes:

The amount of heat transmitted through the fabric that could result in a second-degree skin burn.
Whether the fabric breaks open during exposure.

Whichever threshold occurs first determines whether the garment receives an ATPV or an EBT rating.
Because the testing follows standardized procedures, users can compare certified garments from different manufacturers with confidence.
Why Arc Ratings Matter
An FR coverall is only effective when its arc rating is appropriate for the level of electrical hazard present in the workplace.
Selecting clothing with an insufficient arc rating may leave workers inadequately protected during an arc flash event. Conversely, choosing garments with significantly higher ratings than necessary may increase garment weight and reduce comfort without providing additional practical benefits for the specific task.
Arc ratings help employers match protective clothing to the results of an arc flash risk assessment.
This allows workers to wear garments that provide suitable protection while maintaining mobility and comfort throughout the workday.
Does a Higher Rating Always Mean a Better Garment?
A common misconception is that the highest arc rating is always the best choice.
In reality, the appropriate rating depends entirely on the hazards identified in the workplace.
Higher-rated garments generally contain heavier or more insulating materials, which may affect breathability, flexibility, and comfort. In environments where lower incident energy levels have been determined through a formal hazard assessment, selecting unnecessarily high arc-rated clothing may reduce worker comfort without improving safety.
The goal is not to purchase the garment with the highest number but to select one that provides adequate protection for the anticipated exposure.
Where to Find the Arc Rating on an FR Coverall
Most certified FR coveralls display their arc rating on one or more of the following:

The permanent garment label
Manufacturer's product information
Technical specification sheets
Product catalogues
Compliance documentation

The label will typically state the arc rating followed by the appropriate unit, cal/cm², along with the relevant certification standards.
Workers should always verify the garment's rating before use rather than assuming all FR clothing provides the same level of protection.
Arc Rating Is Only One Part of Garment Selection
Although ATPV and EBT are extremely important, they should not be the only factors considered when selecting FR coveralls.
Other considerations include:

Compliance with applicable safety standards
Fabric durability
Comfort and breathability
Fit and mobility
Work environment
Garment construction
Maintenance requirements

A well-designed FR coverall combines appropriate arc protection with features that allow workers to perform their jobs comfortably and safely throughout long shifts.
Common Misunderstandings About ATPV and EBT
Several misconceptions often lead to confusion when comparing FR garments.
ATPV Is Better Than EBT
This is not correct.
ATPV and EBT simply represent two different ways a fabric reaches its performance limit during testing. Neither rating is inherently superior. Both are recognized arc ratings established through the same standardized test method.
Layering Automatically Doubles Protection
Layering FR garments can increase thermal protection, but the total protective performance depends on the specific garment combination and should not be estimated by simply adding individual arc ratings unless supported by testing or manufacturer guidance.
Maintaining the Protective Performance of FR Coveralls
The protective performance of FR coveralls depends not only on the original fabric but also on proper care throughout the garment's service life.
Workers and employers should:

Follow the manufacturer's laundering instructions.
Inspect garments regularly for excessive wear or damage.
Replace garments with significant tears or compromised seams.
Avoid unauthorized alterations that could affect protective performance.
Keep garments free from flammable contaminants such as oil or grease.

Proper maintenance helps ensure the garment continues to perform as intended when protection is needed most.
Conclusion
Understanding an FR coverall's ATPV or EBT rating is essential for selecting protective clothing that matches the level of electrical hazard present in the workplace. While both ratings are determined through standardized testing, they represent different performance limits: ATPV measures the thermal energy required to reach the predicted burn threshold, whereas EBT identifies the point at which the fabric breaks open under arc exposure.
Neither rating is inherently better than the other. What matters most is choosing a certified FR coveralls with an arc rating that meets or exceeds the incident energy identified through a proper arc flash risk assessment.
By learning how to interpret ATPV and EBT values, safety professionals and workers can make more informed decisions, improve workplace compliance, and ensure FR coveralls provide the level of protection they were designed to deliver.