The Intensity of Arc Flash
AC Arc Flash Hazards
AC arcs are electrical discharges that occur when an alternating current flows through a gap or air space. In AC arcs, the direction of the current constantly changes, resulting in the arc repeatedly extinguishing and reigniting during each cycle. AC arcs can occur in various electrical systems and devices that utilize alternating current, such as power distribution networks, household electrical wiring, electrical appliances, and industrial machinery.
CAT 1 Baselayer
The arc produces a massive fireball, but the garment emerges intact – no fire or breakopen.
CAT 1 Coverall in CAT 2 Arc
Inadequate for the hazard, the AR outer layer is overwhelmed and the cotton base layer ignites.
New CAT 2 Garment
The garment performs admirably, with no fire or significant damage.
Non-AR 100% Cotton Shirt
The front of the garment instantly ignites, and the fire quickly spreads to the back – with catastrophic results.
UltraSoft® AR/FR Coverall After 100 Launderings
The garment performs as designed – and as well as a new garment, with no afterflame or significant damage.
Igniting instantly, the flammable garment is consumed within seconds – melting and dripping away.
Very Lightweight CAT 2 Carhartt AR Shirt
Despite its 4.7oz weight and the size of the arc, the garment performs as expected.
ASTM D6413 Rainwear (CAUTION)
Not compliant with the standard specifically for AR rainwear (ASTM F1891), the rainsuit ignites, breaks open, and melts.
ASTM F1891 AR Rainwear
Compliant with the appropriate AR rainwear standard, the rainsuit emerges fully intact.
Non-AR Outerwear Over AR Clothing
Flammable outer layers ignite and cause an aggressive, sustained fire that burns rapidly and is difficult to extinguish.
Meltable Baselayer Under AR Clothing
The flammable underlayer ignites and instantly melts against the wearer, causing significant or fatal injury.
NSA Enespro® 20 Cal Arc Suit
The garment protects the wearer from both the incident energy and molten copper thrown by the arc.
12 Cal Arc Suit
The garment carbonizes instead of burning, fully protecting the worker – even in this arc above its rating.
Improper Wear – Shirt Untucked
The untucked shirt allows an arc breach – igniting a cotton underlayer and causing burn injury.
Versa AR Outerwear
The jacket is engineered to handle large arcs and performs as expected – showing the importance of a quality AR outerlayer.
Cotton Baselayer Ignition
With an untucked, unbuttoned AR outer layer, the manikin experiences a t-shirt fire that causes significant injury.
DC Arc Flash Hazards
DC is different than AC in that it is “on” throughout the arc, while AC current alternates between “on” and “off,” DC arcs are theoretically harder to stop because they don’t drop below the zero point. They also appear to be more “magnetic” (drawn to metal) and perhaps a bit more energetic vs AC arcs of the same input energy. DC arcs can happen in various contexts, including in electric vehicles (EV) manufacturing and EV charging infrastructure, electrical power systems, industrial settings, renewable energy systems, battery systems, and more.
Overwhelming an Arc-Rated FRMC® Shirt
The incident energy exceeds the shirt’s arc rating, causing slight breakopen but no body burn due to an AR base layer.
Tyndale FRMC® Shirt
The shirt is slightly carbonized and covered in molten copper, but the garments do their job and protect the worker.
Non-AR Hi-Vis Vest Outerwear
The vest ignites and jacket is quickly engulfed, resulting in a prolonged and intense blaze with a catastrophic outcome.
NSA Enespro® 40 Cal Suit
A sacrificial outer layer absorbs the energy, protecting the worker and preventing arc breach.
NSA TECGEN® CAT 2 Shirt
The garment shields the wearer, insulating them from the hazard – with 0% body burn.
The arc ignites the coverall quickly, easily, and persistently – with catastrophic consequences.
Tyndale Arc-Rated Outerwear
The windbreaker is an impenetrable barrier against heat and molten copper, even in this high-energy arc.
The garment chars, insulating the wearer – with no afterflame, breakopen, or signs of compromised integrity.