Arc Rated Clothing
Arc rated clothing is flame-resistant (FR) clothing specifically tested and certified to protect workers from arc flash thermal energy, with a documented arc rating in cal/cm² (ATPV or EBT) that must equal or exceed the estimated incident energy at the worker's location. It is required by NFPA 70E and CSA Z462 for exposures above 1.2 cal/cm², and all arc-rated clothing is FR, but not all FR clothing is arc-rated.
On a shop floor, arc rated clothing is part of the electrical PPE ensemble for energized work on MCCs, switchgear, and panelboards. A Qualified Person performs an arc flash study to determine incident energy (cal/cm²) at each equipment location. Workers select clothing with an arc rating ≥ that energy, or use the PPE category method (e.g., Cat 2 requires ≥8 cal/cm²). Typical ensembles include arc-rated long-sleeve shirts and pants, coveralls, or full suits, plus arc-rated hoods, gloves, and outerwear. All outer garments (hi-vis, rainwear) must be arc-rated. Compliance is managed via task-based PPE matrices and equipment labels from arc flash studies, following CSA Z462 or NFPA 70E standards.
What do ATPV and EBT mean for arc rated clothing?
ATPV (Arc Thermal Performance Value) is the incident energy (cal/cm²) at which the material causes a 50% probability of second-degree burn without breaking open. EBT (Energy Breakopen Threshold) is the incident energy at which the material breaks open (50% probability). The arc rating printed on the garment is the lower of ATPV or EBT for that material or layered system.
How is arc rated clothing tested and certified?
Garments are tested to ASTM F1506 for clothing and ASTM F1891 for rainwear. Test methods like ASTM F1959 expose fabric systems to controlled arc flash conditions, measuring incident energy and predicting burn probabilities and break-open events to derive ATPV/EBT ratings. CSA Z462 explicitly requires arc-rated apparel to meet ASTM F1506 and raingear to meet ASTM F1891.
How do OSHA, NFPA 70E, and CSA Z462 interact in practice for arc rated clothing?
OSHA requires PPE that protects against electrical hazards, referencing NFPA 70E as a consensus standard; failure to use arc-rated clothing can result in citations. NFPA 70E provides detailed requirements for hazard analysis and PPE selection, mandating arc-rated clothing for exposures >1.2 cal/cm². CSA Z462 mirrors NFPA 70E for Canadian workplaces, defining PPE categories and minimum arc ratings; it is non-mandatory but accepted as best practice, often referenced by provincial regulators like WorkSafeBC.