Treated FR Fabric versus Inherent FR Fabric
Arc Flash workwear is typically made from Inherent FR Fabric or Treated FR Fabric. These fabrics use natural fibres, man-made fibres, or a combination of both.
Treated FR Fabric is often more affordable, but can lose FR protection through repeated washing. Research has shown this can happen after as few as 10 wash cycles. The garment looks fine. There is no visual warning, however the clothing may have reduced arc flash protection, which could result in injuries.
Inherent FR Fabric is different. The flame resistance lives in the molecular structure of the fibre itself — not applied as a coating or finish. It cannot wash out because the fibre never received it as an outside treatment.
Common Misconceptions
Inherent FR Fabric goes by a few names in spec sheets and technical documents:
- Inherently flame resistant fabric
- Inherently flame retardant fabric
- Permanent FR fabric
The terminology is worth understanding — “flame retardant” technically refers to materials chemically treated to resist fire, while “flame resistant” refers to fibres that are inherently non-combustible. In practice people use the terms interchangeably, which causes confusion.
A few things worth clarifying:
- Not all FR fabric is arc flash rated. FR means the fabric won’t sustain combustion — it says nothing about arc flash performance. Non-arc-rated FR is common in welding, firefighting, and motorsport, where the hazard profile is different.
- Cotton is neither FR nor arc flash rated. It won’t melt or drip, but it is highly flammable and offers no meaningful protection in an arc flash event.
- Treated FR fabrics can lose effectiveness over time. Chemical treatments degrade with repeated washing, unlike inherent fibres which retain their properties for the life of the garment.
What Is Inherent FR Fabric?
Inherent FR Fabric uses fibres that do not ignite at the molecular level. They do not ignite or melt when exposed to heat. They char at the point of contact and self-extinguish once the heat source is gone.
The most common Inherent FR fibres used in arc flash garments are:
- Aramid fibres — Nomex IIIA (DuPont) is the benchmark for Inherent FR in electrical PPE. A meta-aramid that has been used in protective clothing for decades.
- Modacrylic fibres — a synthetic copolymer that does not combust. Often blended with cotton or FR viscose to improve comfort without sacrificing arc performance.
- Para-aramid fibres — Kevlar is the well-known brand. High strength, typically used as part of a blend rather than on its own.
Inherent vs Treated FR Fabric
Treated FR fabric starts life as a standard material — usually cotton or a cotton blend — and goes through a chemical process to gain flame resistant properties. That treatment works, and when the garment is new it will meet the same standards as an Inherent FR garment.
The difference shows up over time. The chemical treatment sits on or within the fibre rather than being part of it. Repeated washing degrades it. Some treated garments hold their rated protection for up to 50 industrial wash cycles.
Not complying to strict washing instructions also leads to premature degradation and shortens garment lifespan.
Research shows FR properties can drop significantly before that limit.
Inherent FR fabric has no treatment to degrade. The fibre itself does not burn. Whether the garment is washed 10 times or 100 times, the protection level stays the same, if you follow manufacturers’ washing instructions.
For occasional use, Treated FR canbe practical and cost-effective choice. For full-time electrical workers washing their kit weekly, it is a risk most safety managers would rather not take. As a result over time Inherent FR fabric is therefore more cost effective.
Why It Matters for Arc Flash Protection
An arc flash event releases a burst of thermal energy that can cause severe burns in milliseconds. Protective clothing is the last line of defence, and it only works if it is actually performing to spec and fit for purpose
In Australia, the key standards for arc flash protective garments are:
- NFPA 70E – the US standard for electrical safety in the workplace. Sets out arc flash risk assessment procedures and defines four Hazard Risk Categories (HRC 1–4), each with a minimum cal/cm² requirement for PPE.
- ASTM F2178 — the US test method for measuring the arc rating of face protection (hoods and faceshields) specifically, also reported in cal/cm².
- ISO 11612 — Protective clothing against heat and flame.
- AS/NZS 4836 — Safe Working on or Near Low-Voltage Electrical Installations and Equipment.
- IEC 61482-1-1 and IEC 61482-1-2 — the test methods used to determine a garment’s arc rating, measured in class via box test (APC 1 or APC 2).
If a treated garment has degraded through washing, it no longer meets that requirement, even if it was certified when new.
Safe Work Australia Personal Protective Equipment Problems & Maintenance
How Inherent FR Fabric Works
The protection is in the fibre, not on it
Treated FR garments use a flame retardant chemical bonded to the fibre surface. That bond weakens over time with laundering. Inherent FR fabrics have no surface treatment to break down. The fibres simply do not support combustion. That is the material’s natural chemistry.
It self-extinguishes
When exposed to flame, Inherent FR fibres char rather than melt or drip. Once the ignition source is gone, burning stops. Treated Fabrics behave differently – some Treated Fabrics can still melt or drip even if they resist ignition. In arc flash situations this matters, because molten material contacting skin causes serious additional injuries beyond the arc event itself. For arc flash PPE, Inherent FR is the preferred specification for this reason.
Better arc ratings at lighter weights
Aramid-based Inherent FR Fabrics typically achieve higher arc ratings at the same fabric weight as treated alternatives. For workers in hot Australian conditions, that means better protection without a heavier, more uncomfortable garment.
Common Mistakes When Choosing FR Fabric
Assuming certified means permanently protected
A certification confirms how the garment performed at the time of testing. It does not guarantee the fabric type or how long that protection lasts. Always check whether the fabric is Inherent or Treated. The cost of the garment should not be the determining factor of which PPE you choose.
Not tracking wash cycles on treated garments
Treated FR garments typically hold their protection for 50 industrial washes. But protection can drop well before that limit, especially when laundering instructions go unread. You would need strict tracking procedures to monitor the number of washes and ensure PPE is not degraded and therefore still fit for purpose.
Using treated garments for full-time electrical workers
Treated FR is a reasonable option for temporary or infrequent use, however the wash degradation risk of the fabric is not acceptable for electricians and utility workers wearing the same garments daily. Inherent FR Fabric is therefore the logical option for guaranteed protection.
What to Look for When Buying
For arc flash applications in Australia, look for garments that:
- Specify aramid or modacrylic as the primary fibre — not a minor blend component
- Carry an arc rating (ATPV and/or ELIM) matched to your site’s actual exposure level
If you work in a hot climate, modacrylic blends with cotton or FR viscose tend to breathe better than heavier aramid compositions. Volt Safety can help match a garment to your specific exposure level.
Maintenance
Inherent FR Fabric keeps its FR property through all washes, provided manufacturer washing instructions are followed. Below is generalised information on how to wash Inherent FR Fabric. Please follow all washing instructions provided by the manufacturer to ensure the arc flash rating and durability of your garment:
- No bleach or fabric softeners — these damage the fibres.
- Do not wash garments over 60 degrees celsius
- Wash FR garments separately to avoid contamination from flammable oils or residues.
- Check regularly for physical damage — tears, thinning, or soiling that will not come out.
- Any repairs must use FR-rated materials. Non-FR patches or thread compromise protection.
- Replace garments when physically deteriorated.
Summing Up
Over the lifetime of a garment, Inherent FR Fabric can work out cheaper. Because the protection is built into the fibre itself, it doesn’t wash out or degrade the way treated fabrics can. That means fewer replacements, more consistent compliance, and less uncertainty about whether your gear is still doing its job after 50 washes.
The initial investment may be higher. But when you factor in replacement cycles and the cost of non-compliance, Inherent FR clothing often can make more financial sense over time.