Full-Layer Arc Flash Protection: Why Every Clothing Layer Must Be Arc-Rated 

Executive Summary 

Arc-flash events are high-energy electrical faults that generate temperatures exceeding 19,000 °C (≈35,000 °F), capable of igniting or melting clothing in milliseconds. While many organisations rely on a single arc-rated outer garment, modern research and real-world incidents show that any non-arc-rated layer—whether underneath or on top—can undermine the performance of the entire protective system. 

This paper outlines why layered arc protection is essential, provides open-source technical references for arc-flash temperatures, and highlights how VAILOS, as a vertically integrated manufacturer of inherent FR / arc-flash protective fabrics and garments, is working to eliminate the excuses that lead to unsafe layering choices. 

1. The Arc Flash Hazard: Temperature and Energy

Arc-flash temperatures are well documented by independent sources: 

• OSHA notes arc temperatures can exceed 35,000 °F (19,400 °C) — “four times hotter than the surface of the sun.”
  Source: https://www.osha.gov/electrical/flash-hazards 

• Electricity Forum publishes that arcs may range from 2,800 °C up to 19,000 °C, depending on fault type and duration.
  Source: https://electricityforum.com/iep/arc-flash/arc-flash-temperature 

• Academic research (Martins et al.) measuring high-current arcs has documented plasma temperatures exceeding 40,000 K in extreme cases.
  Source: https://arxiv.org/abs/1904.01273 

These temperatures ignite natural fibres and melt common synthetics instantly. They also penetrate multiple clothing layers, which is why layering is a system—not an accessory. 

2. The “Weakest Layer” Effect

Arc-rated PPE is only effective when all layers—from base layer to outer garment—are  arc-rated. The system fails when even a single layer is unsafe. 

2.1 Under Layers (Base Layers) 

Base layers are often the most dangerous point of failure.
Common undergarments—polyester T-shirts, nylon sports tops, spandex thermals—melt at temperatures between 120–260 °C, which is negligible compared with arc-flash heat. 

When heat penetrates an arc-rated outer layer, a melting base layer can: 

• Adhere to skin 

• Intensify burn depth 

• Extend recovery time 

• Cause garment break-open from the inside 

2.2 Over Layers (Outer Shells) 

Non-FR rain jackets, cold-weather gear, or hi-vis vests worn over arc-rated garments introduce similar risks. These items can ignite, melt, or channel heat in ways that defeat the tested performance of the arc-rated layer beneath. 

NFPA 70E explicitly states: 

Outer layers worn over arc-rated PPE must themselves be flame-resistant and must not increase injury. 

3. Standards Perspective

NFPA 70E 

• Clothing must not increase injury. 

• Only non-melting natural fibres are permitted as underlayers if not arc-rated. 

• Outer layers must be FR/AR. 

OSHA 1910.269 

• Garments must not ignite or melt. 

• Layering must not contribute to injury. 

IEC 61482 (Europe/International) 

• Focuses on system performance; garments tested alone may not protect when layered incorrectly. 

Across standards, the message is unified: protection is only real if every layer participates. 

4. Where VAILOS Fits Into the Layering Issue

VAILOS occupies a rare position in the arc-flash PPE landscape:
a vertically integrated manufacturer designing both inherent FR/arc-protective fabrics and finished garments. 

This gives VAILOS capabilities highly relevant to the layering challenge: 

4.1 Control at Fibre, Fabric, and Garment Level 

Because VAILOS engineers its own inherent FR fabrics, the company can: 

• Reduce fabric weight while maintaining protection 

• Improve breathability and comfort 

• Control shrinkage, durability, and heat-transfer performance 

• Test garment systems (multi-layer combinations), not just single pieces 

This is crucial because workers often reject uncomfortable or heavy PPE, leading them to remove layers, wear unsafe substitutes, or bypass PPE altogether. 

4.2 Removing the “Comfort Excuse” 

One of the leading reasons operators fail to wear full-layer arc protection is discomfort: 

• Too hot 

• Too heavy 

• Restricted movement 

• Layers that feel bulky or cumbersome 

VAILOS’ mission directly targets this barrier by developing lighter, more comfortable, more breathable arc-rated options that eliminate the excuses workers rely on to skip PPE. 

4.3 Eliminating Risky Non-FR Layers 

By offering complete FR/AR systems—base layers, mid-layers, outer shells—VAILOS helps employers ensure that no “weak layer” enters the system.
This aligns fully with the safety science documented above: a protective system is only as strong as the least protective layer. 

5. Practical Consequences of Incorrect Layering

Scenario: Synthetic Base Layer 

Worker wears an arc-rated shirt but polyester base layer underneath. Heat penetrates, polyester melts into skin → severe burns. 

Scenario: Non-FR Outer Layer 

Arc-rated shirt under a non-FR hi-vis vest or rain jacket. Outer garment ignites → heat trapped → arc-rated layer ruptures. 

Scenario: PPE Discomfort 

Workers remove arc-rated mid-layer because it’s too warm. Incident energy exceeds the capability of single outer garment → injury that could have been prevented. 

VAILOS addresses this scenario by designing inherently FR fabrics with improved moisture management and weight reduction to reduce user discomfort. 

6. Best Practices for a Safe Layering Policy

1. All layers in arc-hazard zones must be arc-rated or, at minimum, non-melting natural fibres. 

1. Ban synthetic base layers, including sportswear, compression gear, thermals. 

1. Ensure outer layers (hi-vis, rainwear, cold-weather jackets) are arc-rated. 

1. Train workers on why layering matters—and why one arc-rated layer is not enough. 

1. Choose garments tested as a system where possible. 

1. Prioritise comfort-driven PPE to eliminate behavioural non-compliance. 

7. Conclusion

Arc-flash incidents expose workers to extreme thermal conditions far beyond the ignition point of everyday materials. A single arc-rated garment cannot protect a worker whose under- or over-layers melt, ignite, or compromise the garment system. 

Full-layer arc protection is no longer optional—it is fundamental.
VAILOS contributes to this mission by developing lightweight, comfortable, inherently FR garment systems designed to remove the barriers and excuses that have traditionally led workers to wear unsafe layers. 

By combining scientific understanding of arc hazards with integrated fabric-to-garment engineering, VAILOS supports a future in which every worker can be fully protected—comfortably, consistently, and without exception.