Does Arc Rated Clothing Protect Against DC Arcs?

New research confirms arc-rated PPE tested with AC power provides the same protection against DC arcs, offering reassurance as energy storage and DC systems expand across industries.

• By Scott Margolin
• Oct 15, 2025

DC power and energy storage are a large and rapidly growing segment of the American electrical industry. As often happens with this kind of growth, industry and commerce are well ahead of science and safety.  

There was thus an urgent need for arc flash safety experts and manufacturers to better understand DC arc flash and PPE performance. We conducted preliminary qualitative research initially to achieve at least some level of comfort, and then quantitative (data driven) research to definitively address the issue.  

Qualitative Research 

Arc ratings have existed for well over 30 years; however, these ratings have always been conducted with an AC energy source, begging the question “does arc rated clothing and other PPE protect equally against a DC arc hazard?”  

The author conducted qualitative analysis as rapidly as possible, using commercially available garments, the same mannequins, arc box and lab we’ve used for 20+ years in AC. We worked with the laboratory to convert their AC power and our arc box to DC and tested several dozen garments where we have significant experience in AC, using the same incident energies, methodology and test parameters. Visual and forensic analysis of both the garments themselves and super slow-motion video were used to draw preliminary conclusions regarding how well PPE rated using AC performed against DC.  

The DC arc itself differs visually from AC. DC arcs do not display the pulsing nature of an AC arc (because DC is “always on” while an AC arc is “on and off”). DC arcs also appear to be more magnetic; once they start in a certain direction, they tend to continue in that direction.  

However, visual and forensic examination of garments exposed to DC arcs clearly shows no significant difference in PPE performance AC versus DC. There is no visible difference between AC and DC arc interaction with flammable work clothing, meltable work clothing, or arc-rated clothing, including knits, wovens, coveralls, 40 cal suits, rubber gloves, face shields, or hard hats. 

Quantitative Research 

These results are reassuring, but clearly not enough. Quantitative data is required to gain full confidence in PPE performance. The number of arc ratings necessary to supply a statistically relevant degree of confidence across a reasonable number of fiber and fabric types requires considerably more money than any single company in our industry could support, so the author worked closely with Brian Shiels and Kinectrics to assemble a coalition of companies willing to contribute both funds and expertise to determine whether DC art ratings differ from AC ratings. There are three possible outcomes to this research: arc ratings do not vary from AC to DC; arc ratings do vary, but with a predictable ratio, allowing for a “DC Correction Factor;” or arc ratings vary unpredictably, meaning entirely separate DC arc ratings would be required.  

All research was conducted using the full ASTM F-1959/F 1959M-24b. All variables other than AC vs DC were minimized or eliminated. Conversion to DC was achieved by using a 3-phase full-wave rectifier to provide a DC source of equal capacity, and the Rlimit resistor was adjusted to provide nominal 8000A DC arcing current to match that of the AC tests. 

The research was conducted over six days, and the resulting paper was peer reviewed and published by IEEE, meaning that both the methodology and the results were found to be valid. Five fabrics were tested. The four most popular Cat 2 shirt weight fabrics were selected to ensure the research is directly relevant to what's being worn, while the fifth fabric was a laminate with a rating above 30 cals to ensure there isn’t a difference at much higher incident energies.  

Arc ratings were conducted three times in AC arcs and three times in DC arcs for each fabric. Those replicates were then averaged and compared. The data set for one fabric: AC arc ratings of 10.6, 11.4, 11.4 for an average of 11.1; DC arc ratings of 9.9, 11.7, 11.4 for an average of 11. This result was consistent across all 5 fabrics tested. Three of the five fabrics had the same arc rating in AC and DC arcs; one differed by 0.1 cal and one differed by one cal (32 vs 33). Standard deviation was well within the deviation of the test method itself. 

Conclusions 

Efforts to reduce inherent variability were successful; there was no trend of an arc rating of a given fabric increasing or decreasing consistently over successive testing dates. These fabrics show very high precision and low deviation. Our conclusion is that there is no statistically consequential difference in arc ratings when exposed to DC vs AC arcs. Separate DC arc ratings are not necessary, nor is a DC correction factor; arc flash PPE rated using the traditional ASTM F 1959 method with an AC energy source accurately reflects protection levels in DC arcs.  

Path Forward 

This research focused on Cat 2 shirting fabrics and trilaminate arc suit fabric. There are many other fabrics and products in common use, so the author is currently raising funds to confirm these results extend to other relevant PPE. We intend to test multi-layer fabric systems, fall protection, face protection, and hand protection over the coming year.   

We have no reason to suspect any meaningful difference in within most of these other categories, but due diligence demands we do the work. It is highly reassuring to finally have research that confirms existing AR PPE protects equally in both AC and DC arc flash.   

This article originally appeared in the October 2025 issue of Occupational Health & Safety.