Arc flash is one of the most serious thermal hazards in electrical, mining and utility work. Arc-rated clothing is the protection you rely on when your site's other controls cannot remove the hazard, so its label has to be read correctly. This guide explains the two ratings you will see most often: ATPV and CAT levels.
What does ATPV mean?
ATPV stands for Arc Thermal Performance Value. It is a fabric's arc rating, measured in cal/cm²: the amount of heat energy at which there is a 50% chance of a second-degree burn to the skin under the fabric. The higher the ATPV, the more protection the fabric gives.
Arc ratings come from laboratory arc testing, such as ASTM F1959 or IEC 61482-1-1. Test results can also include the EBT (Energy of Breakopen Threshold): the energy at which there is a 50% chance the fabric breaks open. By definition, a garment's arc rating is whichever of the ATPV and the EBT is lower. In practice, compare the cal/cm² figure on the label or product page with the rating your site requires.
What do CAT levels 1 to 4 mean?
CAT levels (also written as PPE categories or HRC, short for Hazard Risk Category) group arc-rated clothing by its minimum arc rating. The 1 to 4 system comes from NFPA 70E in the US, and you will see it on many garment labels and product pages, usually next to the cal/cm² figure.
| CAT level | Also written as | Minimum arc rating |
|---|---|---|
| CAT 1 | PPE 1, HRC 1 | 4 cal/cm² |
| CAT 2 | PPE 2, HRC 2 | 8 cal/cm² |
| CAT 3 | PPE 3, HRC 3 | 25 cal/cm² |
| CAT 4 | PPE 4, HRC 4 | 40 cal/cm² |
Always check your site's hazard assessment. It, not the garment, sets the category a task needs. Choose clothing whose arc rating meets or exceeds the figure the assessment calls for.
What do arc ratings look like on real garments?
Labels do not all follow one format. Some brands quote a category, some quote an ATPV, and some quote both. These examples are taken from product pages in our FR range:
| Garment | What the listing states |
|---|---|
| Portwest Bizflame Work FR Pants FR431 | ATPV 9.1 cal/cm² (ASTM F1959) |
| Bisley APEX 240 Taped Biomotion FR Ripstop Pant BP8580T | PPE 2, 8 cal/cm² (NFPA 70E:2018); ATPV 11 |
| DNC Patron Saint Flame Retardant Cargo Pants 3419 | ATPV 14 cal/cm², HRC 2 (ASTM F1959) |
| KingGee FR Wet Weather Jacket Y06730 | ATPV 34, PPE 3 |
Because brands present the numbers differently, compare the cal/cm² figure with what your site assessment requires, not the category name alone.
Which Australian standards apply to arc flash?
AS/NZS 4836:2023 covers safe working on or near low-voltage and extra-low-voltage electrical installations and equipment, including managing arc flash and arc blast hazards. For clothing, Energy Networks Australia's ENA NENS 09-2014 is the national guideline for the selection, use and maintenance of personal protective equipment for electrical arc hazards.
A garment's own arc rating comes from laboratory test standards such as ASTM F1959 or IEC 61482-1-1, so check that the label or product page states the cal/cm² figure and the test standard behind it. Your safety officer or electrical supervisor can confirm which documents your site works to.
Shop FR clothing
Our FR range includes pants, jackets, coveralls and shirts from Bisley, DNC, KingGee and Portwest. Flame resistant is not the same as arc rated: garments made for welding or flash fire may state no arc rating, so look for the cal/cm² figure and the test standard on each product page. Our FR clothing guide explains the difference.
Or go straight to FR pants, FR jackets and FR coveralls. Have questions about your site's requirements? Contact our team.
1st Safety is based in Auburn, NSW, and supplies AS/NZS-compliant PPE to trades, construction, and industrial businesses across Australia.
Frequently Asked Questions
What does ATPV stand for?
ATPV stands for Arc Thermal Performance Value. It is a fabric's arc rating in cal/cm²: the heat energy at which there is a 50% chance of a second-degree burn to the skin under the fabric. A higher ATPV means more protection.
What is the difference between ATPV and EBT?
Both are results from arc testing, measured in cal/cm². ATPV is the energy at which a second-degree burn becomes 50% likely. EBT (Energy of Breakopen Threshold) is the energy at which the fabric is 50% likely to break open. A garment's arc rating is whichever of the two is lower.
What are CAT levels for arc flash protection?
CAT levels (also called PPE categories or HRC) run from 1 to 4 and call for a minimum arc rating of 4, 8, 25 and 40 cal/cm² respectively. CAT 4 is the highest category. Your site's arc-flash assessment decides which one a task needs.
What does CAT 2 mean for arc flash PPE?
CAT 2 (also written PPE 2 or HRC 2) means arc-rated clothing with a rating of at least 8 cal/cm². CAT 1 needs at least 4 cal/cm² and CAT 3 at least 25. Your site's arc-flash assessment decides which category a task needs.
What does an ATPV of 12 cal/cm² mean?
It means there is a 50% chance of a second-degree burn under the fabric at 12 cal/cm² of incident energy. That is above the 8 cal/cm² CAT 2 minimum and below the 25 cal/cm² CAT 3 minimum. For any ATPV figure, compare it with the rating your site assessment requires.
Which Australian standard covers arc flash?
AS/NZS 4836:2023 covers safe working on or near low-voltage and extra-low-voltage electrical installations, including arc flash and arc blast hazards. For clothing, the Energy Networks Australia guideline ENA NENS 09-2014 covers the selection, use and maintenance of PPE for electrical arc hazards. A garment's arc rating comes from tests such as ASTM F1959 or IEC 61482-1-1.
How do I know what CAT level I need?
Check your site's hazard assessment to find the required CAT level before choosing FR workwear, then choose clothing whose arc rating meets or exceeds it. If you are unsure, ask your safety officer or electrical supervisor.