Arc Flash & Fire Protection: Custom Inorganic Barrier Materials for Utility Power
H-O Products die-cuts, waterjet-cuts, and converts inorganic and glass-reinforced barrier materials — mica laminate sheet (muscovite and phlogopite), ManniGlas-class glass-fibre paper, ceramic-free glass papers, glass-epoxy laminate (G10 / FR4 / G11), Durostone composite, heat-shield silicone foam, and FST-documented elastomers — into phase barriers, compartment fire barriers, cable-penetration barrier stacks, and BESS fire-blocking layers for utility-scale power, built to your drawing.
Built for: MV / HV substation and switchgear-lineup phase barriers and compartment baffles, generation-plant bus and cable-penetration barriers, BESS module-to-module and enclosure fire barriers, and the smoke-and-toxicity-sensitive layers inside enclosed MCC (motor control center) and electrical rooms.
To choose a utility arc-and-fire barrier material, work from the duty. Arc-fault / phase barrier (MV / HV switchgear): specify muscovite mica sheet as the inorganic containment face, phlogopite mica for the hottest bands, and G10 / FR4 or Durostone where the barrier bears load (UL 94 class and IEC 60112 CTI per the laminate TDS). Compartment / cable-penetration fire barrier: ManniGlas-class glass-fibre paper lining the steel (non-combustible.
The remaining zones and duties are mapped in the When-to-spec list on this page. Values are per the TDS on file; see the material reference below for ordering details.
Assembly / installation, by designation (the rating belongs to the tested assembly or the PPE program): IEEE C37.20.7 (internal arcing-fault test for switchgear) · IEC 62271-200 (MV switchgear arc-fault classification) · NFPA 70E (electrical safety in the workplace; arc-flash PPE program) · NFPA 855 (installation of stationary energy storage). Material-level, per the maker TDS: UL 94 (flammability class, incl.
V-0 on the rated grades) · IEC 60112 (comparative tracking index, CTI) · IEC 60243 / ASTM D149 (dielectric strength) · ASTM D495 (high-voltage low-current dry arc resistance) · ASTM E662 (specific optical density of smoke) · ASTM E162 (surface flammability under radiant heat) · ASTM C177 (thermal conductivity) · ASTM D229 / IEC 60893 (rigid laminate methods).
- Arc-fault containment face: muscovite mica sheet
- Hottest-band barrier: phlogopite mica
- Load-bearing phase barrier: G10 / FR4 or Durostone
- Compartment / penetration fire barrier: ManniGlas-class glass-fibre paper
- High-temperature barrier liner: mica barrier sheet
- Highest-CTI structural isolation: Durostone composite
- Heat-shield gasket beside hot zones: heat-shield silicone foam
- Enclosed-room smoke/toxicity: FST neoprene / kSil® V-0
- Higher-temperature glass-epoxy: G11 (NP511)
This guide is for substation and switchgear design engineers, generation-plant and BESS packagers, and MCC / electrical-room designers specifying phase barriers, compartment and cable-penetration fire barriers, and FST-governed room layers for utility-scale power — plus the procurement and sourcing teams qualifying a made-to-order converted barrier part and its documentation.
Arc / fire / FST duty → material selection → converted barrier → production supply.
- 1Name the dutyArc-fault containment, compartment or penetration fire blocking, or a smoke-sensitive occupied room.
- 2Set the structural roleLoad-bearing plate or a conformable lining / gasket layer.
- 3Climb the temperature ladderElastomer to glass-epoxy to glass-fibre / ceramic paper to mica, only as far as the TDS band requires.
- 4Confirm the data lineThe UL 94 class, CTI, or FST value the program calls out is actually on that grade’s TDS.
- 5Die-cut / waterjet to drawingBarrier cut to the compartment, penetration, or module footprint with finished edges.
- 6Quote prototype or productionPrototype quantities through full production runs, with lot-code TDS records.
Where are you in the spec process?
This page serves engineers who already know the barrier material they want and engineers still assembling the barrier stack duty by duty. Pick the path that matches where you are; you do not have to read the rest.
Send a drawing, get a quote
A mica grade, a glass-fibre paper, a G10 / FR4 phase barrier, a Durostone plate, a heat-shield foam gasket, an FST-room lining, or a complete compartment barrier stack on your drawing.
Skip to the quote form →Build the barrier stack duty by duty
Six selection factors (duty, structural role, temperature band, tracking, smoke/toxicity, and the standards framing), a requirement-driven barrier-finder, and nine material families with TDS-cited methods and by-designation assembly language.
Start with selection factors →
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1Send drawingUpload a DXF, STEP, or PDF, or describe the compartment, penetration, or room. A sample part works too.
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2Material reviewEngineering reviews the duty (arc-side, fire-side, or FST-room), the structural role, and the temperature band against the maker TDSs, and frames the standards language correctly: material classes (UL 94, CTI, FST) by TDS; assembly arc qualification (IEEE C37.20.7) and installation context (NFPA 855) by designation, with the rating belonging to the tested design.
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3PrototypeSamples typically ship in 3–5 business days for common and waterjet configurations on materials we keep on hand. Made-to-order; MOQ varies by material and part.
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4ProductionStandard production runs ship about 2 weeks after drawing approval, on flatbed die-cutting, waterjet cutting for thick mica and composite plate, and kitting for compartment barrier stacks. Ongoing parts run with material traceability and lot-code TDS records.
Which barrier problem are you solving?
Application Zones
Utility power concentrates arc-fault and fire risk in four places: the substation and switchgear lineup, where phase barriers and compartment baffles keep a bus fault inside its compartment; the generation plant, where isolated-phase bus, cable trays, and fire-rated wall penetrations carry the risk; the BESS, where module-to-module and enclosure fire barriers and cable-penetration stacks answer to NFPA 855 at the installation level; and the enclosed MCC or electrical room, where smoke and toxicity (FST) decide what elastomers are allowed.
Click a tab to see the barrier stack, the controlling properties, and the families H-O converts for that zone. The layer diagram below the tabs reads the stack in true order from the arc side.
Substation phase barriers & compartment baffles
An MV or HV switchgear lineup contains the arc fault by geometry: phase barriers between bus phases and to ground, and compartment baffles between vertical sections, keep a bus-fault plasma and its pressure pulse inside the compartment where it started. The barrier that faces the arc is inorganic: muscovite mica laminate sheet is non-carbonizing and dimensionally stable through thermal shock, so it does not add fuel or track.
Where the barrier also carries structural load — a standoff, a bolted baffle, a phase-separator plate — glass-epoxy laminate (G10 / FR4, and G11 / NP511 for the higher-temperature step) and Durostone composite bring the mechanical strength with a UL 94 class and an IEC 60112 CTI on the laminate TDS.
One sentence governs the whole zone: arc-resistant switchgear is qualified as a complete assembly per IEEE C37.20.7 (accessibility types 1 / 2 / 2B) and IEC 62271-200; the barrier materials support that tested design and bring their own TDS data lines, they do not carry an arc rating.
Generation plants: compartment & cable-penetration fire barriers
Thermal, gas, and hydro generation plants carry the fire risk along the bus and the cable runs: isolated-phase and non-segregated bus enclosures, cable trays feeding auxiliaries, and the penetrations where power and control cable pass a fire-rated wall between the switchgear room and the plant.
The fire-side barrier here is a non-combustible liner: ManniGlas-class glass-fibre paper (grades in the 1200 / 1900 / 1902 / 2000 family carry UL 94 V-0 file classes and ASTM C177 thermal-conductivity data per TDS) lines the steel and layers into cable-penetration stacks; ceramic-paper barrier duty sits in the same inorganic band.
Mica barrier sheet steps in for the high-temperature band. Where a penetration must seal an expanding gap under fire, intumescent products are part of the firestop system, installed and tested at the assembly level; H-O converts the inorganic barrier and backing layers of such stacks by designation and does not certify a firestop system.
BESS fire barriers & cable-penetration stacks
A battery energy storage system concentrates the fire problem into the module and the enclosure: module-to-module and rack-to-rack barriers slow a thermal event between neighbors, enclosure fire-blocking layers keep it inside the unit, and cable-penetration barriers block propagation along the runs that leave the enclosure. The barrier materials are the same inorganic families, to the module and rack footprint: ManniGlas-class glass-fibre paper and mica barrier sheet for the non-combustible layers, glass-epoxy where the barrier also mounts hardware.
Installation is governed for spacing, capacity limits, and the documentation the AHJ (authority having jurisdiction) reviews by NFPA 855, cited by designation. As with switchgear, the barrier materials support a design evaluated to the standard; the evaluation and any listing belong to the tested system, and H-O supplies the converted layers and their TDS records, framed cautiously per the vendor TDS.
Enclosed MCC & electrical rooms: the FST zone
Inside an enclosed, often occupied MCC or electrical room, the governing question changes from “does it burn” to “what does it do to the air.” Smoke obscuration and toxicity (FST — flame, smoke, toxicity) decide what elastomers are allowed, because a gasket or lining can hold a flame class and still fill an occupied room with smoke.
The families here report the FST data on their own TDS: low-smoke low-flame low-toxicity (FST) neoprene carries UL 94 V-0 with ASTM E662 smoke-density data, and kSil® V-0 silicone sponge reports ASTM E162 / E662 on the super-soft grade TDS for the sealing side.
Heat-shield silicone foam gaskets the hot zones with D495 dry-arc data on its sheet. NFPA 70E frames the electrical-safety work and the arc-flash PPE program in the room, cited by designation; it governs the workplace, not a material.
Six decisions that drive your barrier-material spec
A utility barrier is a single-purpose layer with one controlling property, and the failure is rarely immediate: an organic barrier ages in a radiant zone it only survived in a flame test, a class was assumed from the polymer family instead of read from the grade’s TDS, or a barrier tracks in a dusty compartment long before it ever punctures.
Materials carry classes; assemblies carry ratings. UL 94 V-0, an IEC 60112 CTI, and ASTM E662 smoke data belong to a material grade per its TDS. An arc rating (cal/cm²) belongs to the tested arc-resistant switchgear assembly (IEEE C37.20.7) or to an arc-rated PPE program (NFPA 70E context). Write material classes on the barrier callouts, cite the assembly and installation standards by designation, and never let a drawing imply that a sheet is “arc-rated” on its own: the barrier supports a design evaluated to the standard.
Arc-fault containment is qualified on the complete tested switchgear assembly — accessibility types 1, 2, and 2B. The mica, glass-epoxy, glass-fibre paper, and Durostone layers on this page are the converter-side ingredients of that qualification; the result belongs to the tested design, which is why this page cites the designation and never claims an arc rating for a material.
Read the six factors below in order. The first two frame the duty and the structural role; the next two climb the temperature ladder and defend against tracking; the last two handle the enclosed-room smoke question and lock the standards language. Every factor names its test method, because in this application the documentation is part of the part.
Show all 6 selection factors tap to expand
Duty first: arc-side, fire-side, or FST-room
Rule — Decide whether the barrier faces an arc-fault event, blocks fire propagation through a compartment or penetration, or lines a smoke-sensitive occupied room — then let that pick the family.
The three duties call for different physics. An arc-side barrier wants an inorganic, non-carbonizing face (mica) that survives plasma and radiant flash without adding fuel. A fire-side barrier wants a non-combustible liner (glass-fibre paper, mica barrier sheet) that blocks heat and flame along a boundary. An FST-room layer wants documented low smoke and toxicity (FST neoprene, kSil® V-0) so a gasket does not fill an occupied room with smoke. Name the duty on the drawing; a barrier optimised for one duty is rarely the right pick for another. [1]
Structural role: load-bearing plate or conformable lining
Rule — Split the barrier by whether it also carries mechanical load: a bolted plate wants glass-epoxy or Durostone; a lining or gasket wants paper, foam, or flexible mica.
A phase-separator plate, a standoff, or a bolted baffle bears load and must not crack at a torqued joint, so it is glass-epoxy laminate (G10 / FR4 / G11) or Durostone composite, with the mechanical strength and the CTI on the laminate TDS. A compartment liner, a cable-penetration layer, or a hot-zone gasket only has to cover and conform, so it is glass-fibre paper, mica barrier sheet, or heat-shield silicone foam. State whether the barrier mounts hardware or bears load; that single fact sends the spec down the rigid-plate or the flexible-liner track. [8]
Temperature band: climb the inorganic ladder only as far as the TDS requires
Rule — Order the families qualitatively — elastomer, glass-epoxy, glass-fibre / ceramic paper, mica — and step up only to the band the vendor TDS supports for the exposure.
Continuous radiant exposure beside hot bus is a different problem from a brief fault-event flash. An elastomer or glass-epoxy that survived a flame test can age, embrittle, and shrink in a continuous radiant zone. The inorganic ladder climbs from elastomer to glass-epoxy to glass-fibre / ceramic paper to mica; muscovite mica sits below phlogopite, which the maker designates for the hottest bands.
Distinguish continuous from fault-event exposure on the drawing and pick the family whose TDS band covers the continuous case, not just the flame test. No specific service-temperature limit is printed here; the maker TDS band governs.
Tracking: the failure that arrives before dielectric puncture
Rule — In a dusty or condensing compartment, check the comparative tracking index (CTI, IEC 60112) on the barrier TDS, not just its bulk dielectric strength.
A barrier in a contaminated, humid switchgear compartment fails by surface tracking — a carbonised conductive path that creeps across the surface — long before the bulk material punctures. Dust films and condensation feed it. The number that predicts it is the comparative tracking index (CTI per IEC 60112) on the laminate or composite TDS; Durostone and the glass-epoxy grades carry it.
Call out the CTI requirement for any barrier in a dusty or condensing location, and pair it with dielectric strength (IEC 60243 / ASTM D149) and dry-arc resistance (ASTM D495) where the surface sees an arc. [6]
Smoke & toxicity: the enclosed-room callout most drawings miss
Rule — For an enclosed, occupied electrical room, put ASTM E662 (smoke optical density) and ASTM E162 (radiant flame spread) on the callout, not just a UL 94 class.
A material can hold a UL 94 flame class and still fill an enclosed room with dense smoke, which is the failure that strands an occupied MCC or electrical room. The FST data — specific optical density of smoke (ASTM E662) and surface flammability under radiant heat (ASTM E162) — is a separate line on the TDS, and it is the line that governs an occupied space.
FST neoprene and kSil® V-0 silicone sponge report it. Add the FST requirement to the callout for any enclosed occupied room; inorganic families (mica, glass-fibre paper) sidestep it by not burning. [11]
Standards framing: classes on the material, ratings on the assembly
Rule — Write UL 94, CTI, and FST classes per TDS on the barrier callout; cite IEEE C37.20.7, IEC 62271-200, NFPA 70E, and NFPA 855 by designation, with the rating on the tested assembly.
The most expensive barrier failure is a documentation failure: a drawing note that claims a sheet is “arc-rated,” or a material chosen with a class nobody can trace to a TDS, and the qualification review stalls. Keep the two levels separate. Material classes (UL 94, CTI per IEC 60112, FST per ASTM E662 / E162) come from the grade TDS and go on the part callout.
Arc qualification (IEEE C37.20.7 / IEC 62271-200) and installation context (NFPA 855) attach to the tested design; the workplace arc-flash program (NFPA 70E) governs the PPE, not the barrier. Cite by designation and let the tested assembly carry the rating. [3]
Barrier Selection Tools
Two tools to take you from “we have an arc-and-fire barrier to spec” to here is the shortlist of families for the drawing set: a requirement-driven barrier-finder that dims the families that do not cover your duty, and a side-by-side comparison of every family on this page.
1. Barrier-finder coverage board
Toggle the requirements your barrier carries. The nine families below dim to show which ones cover every requirement you have checked; a covered family stays lit, a family that misses one requirement dims. This is a shortlisting aid, not a certification: material classes (UL 94, CTI, FST) come from the grade TDS, and assembly arc qualification (IEEE C37.20.7) and installation context (NFPA 855) are cited by designation, with the rating on the tested design. The static list below is fully rendered for no-JS and crawlers.
Families covering all checked requirements: 3 of 9
Each family below is tagged with the requirements it covers. Check the requirements your barrier carries; families that miss one dim out. The families that stay lit are the shortlist to put on the drawing for the engineering review.
- Muscovite mica sheetarc face · high-temp
- Phlogopite micaarc face · highest-temp
- Mica barrier sheetfire liner · high-temp
- ManniGlas-class glass-fibre paperfire liner · non-combustible
- Glass-epoxy G10 / FR4structural · CTI · V-0
- Durostone compositestructural · highest CTI
- Glass-epoxy G11 (NP511)structural · higher-temp
- FST neopreneFST room · V-0
- kSil® V-0 silicone spongeFST room · sealing side
2. Side-by-side: barrier-family comparison matrix
Every family called out on this page, with construction, the class that drives its selection, the standards its TDS cites, and the zone it serves. Click a column header to sort. Click any material name to jump to its accordion entry.
| Material | Construction | Selection class | Standards on the TDS / by designation | Zone | |
|---|---|---|---|---|---|
| Arc-side containment (inorganic face) | |||||
| Muscovite Mica Laminate SheetInorganic mica | Mica laminate sheet | Arc containment face | Non-carbonizing; UL 94 / TDS data lines | Substation, BESS | |
| Phlogopite Mica SheetInorganic mica | Mica laminate sheet | Highest-temperature band | Maker high-temp designation; per TDS | Substation | |
| Durostone CompositeGlass-composite laminate | Rigid composite plate | Structural isolation, highest CTI | UL 94 V-0; IEC 60112 CTI (per TDS) | Substation | |
| Fire-side barriers (non-combustible liners) | |||||
| ManniGlas-Class Glass-Fibre PaperInorganic paper | Glass-fibre barrier paper | Non-combustible fire liner | UL 94 V-0; ASTM C177 (per TDS) | Generation, BESS | |
| Mica Barrier SheetInorganic mica | Mica barrier sheet | High-temperature liner | Non-combustible; per TDS | Generation, BESS | |
| Glass-Epoxy G10 / FR4 / G11Glass-epoxy laminate | Rigid glass-epoxy plate | Structural + CTI barrier | UL 94 V-0; IEC 60243 / 60112 (per TDS) | Substation, generation | |
| Heat-Shield Silicone FoamSilicone foam | Conformable silicone foam | Hot-zone gasket / heat shield | ASTM D1056 / D149 / D495 (per TDS) | Generation, MCC room | |
| FST room (enclosed occupied electrical rooms) | |||||
| FST NeopreneLow smoke / flame / tox | Closed-cell neoprene | FST-documented room gasket | UL 94 V-0; ASTM E662 (per TDS) | MCC / electrical room | |
| kSil® V-0 Silicone SpongeFST-documented sponge | Closed-cell silicone sponge | FST sealing-side sponge | ASTM E162 / E662 (per TDS) | MCC / electrical room | |
Skip ahead and request your barrier-material review now
If your drawing set already calls out a mica grade, a glass-fibre paper, a G10 / FR4 or Durostone plate, a heat-shield foam, or an FST-room lining, send it over for review against the TDSs and the standards language.
Barrier-material failures you can prevent at spec
Utility barriers fail quietly first: an organic layer that aged in a radiant zone, a class assumed from the polymer family, a barrier that tracked in a dusty compartment, a smoke number nobody put on the callout, or a drawing note that claimed a rating a material cannot carry. Five patterns cover most of it, and each is a specification decision made before the first part is cut.
In arc-and-fire work, the paperwork is part of the part. A correct material with an undocumented class, or a drawing that claims an arc rating for a component, costs more schedule at qualification review than any cutting error. Cite material classes (UL 94, CTI, FST) per TDS and assembly / installation standards by designation, and never call a barrier “arc-rated.”
Show all 5 failure modes tap to expand
1. An organic barrier that survived the flame test, then aged in the radiant zone
Fix — Distinguish continuous radiant exposure from a brief fault-event flash, and step up the inorganic ladder to a family whose TDS band covers the continuous case.
A barrier was chosen on a flame-test result and installed beside continuously hot bus. Months later it has embrittled, shrunk, or crazed, because a brief-exposure flame class says nothing about years of continuous radiant heat. The failure is slow and easy to miss until the barrier no longer covers its footprint.
The remedy is to read the duty correctly: continuous radiant zones climb the inorganic ladder to glass-fibre paper or mica (muscovite, then phlogopite for the hottest bands), whose maker TDS bands cover sustained exposure, while an elastomer or glass-epoxy stays where the exposure is a fault-event transient.
No service-temperature number is invented here; the TDS band governs. [10]
2. A flammability class assumed from the polymer family, not read from the grade
Fix — Read the UL 94 class off the specific grade’s TDS, and put that grade — not the family — on the callout.
“It is a glass-epoxy, so it is V-0” is the assumption that stalls a qualification review, because UL 94 classes are grade-specific, not family-wide: one FR4 grade carries a V-0 file class and a neighboring grade does not. The same trap catches silicone foam and neoprene, where only the FST-documented grades report the smoke and toxicity data an enclosed room needs.
The remedy is to treat the class as a property of the grade: name the exact grade on the drawing, confirm the UL 94 class (and CTI, and FST where relevant) is on that grade’s TDS, and let H-O supply the lot-code TDS record that backs it. [5]
3. A barrier that tracked in a dusty compartment long before it punctured
Fix — For a barrier in a contaminated or condensing compartment, specify the comparative tracking index (CTI, IEC 60112), not just bulk dielectric strength.
The barrier held its dielectric strength on paper and still failed, because the failure was on the surface: a carbonized conductive path crept across a dust film in a humid compartment, and surface tracking arrived long before bulk breakdown. A high dielectric strength and a thick section do not prevent it; a high CTI does.
The remedy is to make CTI (IEC 60112) an explicit requirement for any barrier in a dusty or condensing location, choose a laminate or composite grade (Durostone, the glass-epoxy grades) whose TDS carries the CTI you need, and pair it with dry-arc resistance (ASTM D495) where the surface also sees an arc.
4. A smoke number that was never on the callout for an occupied room
Fix — For an enclosed occupied electrical room, add ASTM E662 (smoke) and ASTM E162 (radiant flame) to the callout, and pick an FST-documented grade.
A gasket held a UL 94 flame class and passed its bench test, but in a real event it filled an enclosed MCC room with dense smoke, because the flame class says nothing about smoke obscuration or toxicity. The FST data — specific optical density of smoke (ASTM E662) and surface flammability under radiant heat (ASTM E162) — is a separate TDS line, and it is the one that governs an occupied space.
The remedy is to add the FST requirement to the callout for any enclosed occupied room, specify an FST-documented grade (FST neoprene, kSil® V-0 silicone sponge), or move to inorganic families (mica, glass-fibre paper) that sidestep the smoke question by not burning. [11]
5. A drawing note that claimed an arc rating a material cannot carry
Fix — Keep the two levels separate: material classes per TDS on the barrier callout; arc qualification (IEEE C37.20.7) and installation context (NFPA 855) by designation, with the rating on the tested assembly.
A drawing note read “arc-rated mica barrier,” and the qualification review stopped, because an arc rating (cal/cm²) is a property of the tested arc-resistant switchgear assembly (IEEE C37.20.7 / IEC 62271-200) or of an arc-rated PPE program (NFPA 70E context) — never of a sheet of mica, glass-epoxy, or glass-fibre paper. The material brings its own classes and TDS data lines and supports a design evaluated to the standard; it does not inherit the assembly’s rating.
The remedy is to write the material classes (UL 94, CTI, FST) per TDS on the callout, cite the assembly and installation standards by designation, and let the tested design carry the arc rating. H-O supplies the converted barrier and its documentation; the switchgear or BESS designer owns the qualification. [1]
Material reference
Nine families · every value per the maker TDS on file
Inorganic first, only as far as the TDS band requires
Detailed specs for the nine barrier families referenced on this page: the arc-side faces (muscovite and phlogopite mica), the fire-side liners (mica barrier sheet, ManniGlas-class glass-fibre paper), the structural barriers (G10 / FR4 / G11 glass-epoxy, Durostone composite), the heat-shield layer (silicone foam), and the FST-room layers (FST neoprene, kSil® V-0 silicone sponge).
Values are per the maker TDS on file for each grade with the method named; assembly and installation standards are cited by designation only, with the rating belonging to the tested design. H-O die-cuts, waterjet-cuts, slits, and laminates every family to drawing.
Muscovite Mica Laminate Sheet (Rigid / Flexible)Arc-containment face · inorganic, non-carbonizing · / waterjet to drawing
Cautious language is part of this material’s spec: the barrier supports an arc-fault containment design qualified on the tested switchgear assembly per IEEE C37.20.7. H-O supplies the converted mica layer and its documentation; the switchgear designer owns the qualification. The material is not “arc-rated” on its own.
Phlogopite Mica High-Temperature SheetHighest-temperature band · inorganic, non-combustible · the step above muscovite
Order the mica families qualitatively by the maker temperature designation, not by an invented degree limit; the TDS band governs. Non-carbonizing and non-combustible, it sidesteps the smoke question by not burning.
Mica Barrier Sheet (Compartment Liners)High-temperature fire-barrier liner · inorganic · compartment & penetration layers
Where a penetration must seal an expanding gap under fire, intumescent products are part of the firestop system, installed and tested at the assembly level. H-O converts the inorganic barrier and backing layers of such stacks by designation and does not certify a firestop system.
ManniGlas-Class Glass-Fibre PaperNon-combustible fire-barrier paper · ceramic-free · UL 94 V-0 file classes per TDS
Grades carry their UL 94 file class and ASTM C177 thermal data on the maker TDS; specify the grade by name so the class is traceable. Ceramic-paper barrier duty sits in the same inorganic band where a design calls for it.
Glass-Epoxy Laminate G10 / FR4 / G11 (NP500A / NP510A / NP511)Structural phase barriers & baffles · FR4 UL 94 V-0 per TDS · CTI on the laminate data
Specify the grade by name (G10 / FR4 / G11, or the NP500A / NP510A / NP511 designation) so the UL 94 class and the CTI are traceable to that grade’s TDS. The deep laminate story lives on the power-distribution electrical-insulation sibling page.
Durostone Composite LaminateStructural isolation, highest CTI · UL 94 V-0 + IEC 60112 CTI per TDS
Where surface tracking is the governing risk, Durostone’s CTI (per IEC 60112 on the TDS) is the number to check; pair it with dry-arc resistance (ASTM D495) where the surface also sees an arc.
Heat-Shield Silicone Foam (BISCO® RF / IF family)Conformable hot-zone gasket / heat shield · D1056 / D149 / D495 per TDS
Specify closure force, gap, and any flame-class or dry-arc requirement; the grade TDS carries the compression class (D1056), the dielectric (D149), and the dry-arc data (D495).
FST Neoprene (Low Smoke / Low Flame / Low Toxicity)Enclosed-room gasket / lining · UL 94 V-0 + ASTM E662 smoke data per TDS
Put ASTM E662 (smoke) on the callout for any enclosed occupied room, and specify the FST-documented grade so the smoke and toxicity data is traceable. NFPA 70E frames the room’s electrical-safety work by designation.
kSil® V-0 Silicone Sponge (FST-Documented Grades)Sealing-side sponge · ASTM E162 / E662 on the super-soft grade TDS
The FST data lives on the super-soft grade TDS; specify the grade so the E162 / E662 data is traceable to it. For enclosed rooms, the smoke number governs alongside the flame class.
AeroZero® Polyimide-Aerogel Film — BESS Barriers (Blueshift)Thin thermal-runaway barrier tier for BESS modules · not an arc-rated material
- AZ-TPS 100 · AZ-TPS 101 single- and double-sided silicone-PSA aerogel film, 190–216 µm, UL 94 VTM-0
- AZ-TPS PI 100 polyimide-faced aerogel film, 240 µm, UL 94 VTM-0 — durable outer skin for handling and wear
- TripleZero TPS 300 three-layer aerogel laminate, 570 µm, UL 94 V-0 — passes the FAR 25 Appendix F 12-second vertical burn per manufacturer data
- QuinZero TPS 501 five-layer laminate with acrylic interlayers, 953 µm — maximum thermal resistance per part; acrylic interlayers limit service temperature vs. silicone grades, verify on the TDS
Arc-and-fire barrier materials: engineer-grade FAQ
Twelve of the questions we hear most from substation, generation, BESS, and electrical-room teams. If your question is not here, send a drawing or call, engineering picks up.
Can a mica or glass-epoxy barrier be “arc-rated”?
No, and no honest supplier will say otherwise. An arc rating (cal/cm², ATPV/EBT) belongs either to arc-resistant switchgear qualified as a complete assembly per IEEE C37.20.7 / IEC 62271-200, or to an arc-rated PPE garment/program tested to ASTM F1959 in the NFPA 70E context. A sheet of mica, glass-epoxy, glass-fibre paper, or composite does not carry an arc rating.
What the barrier materials carry is their own documentation: material-level classes (UL 94, IEC 60112 CTI, ASTM E662 smoke), the test methods behind their properties, and lot-code traceability. They support a design qualified to the assembly standard; H-O supplies the converted layers and the paperwork, and the switchgear or BESS designer owns the qualification. [1]
What goes between bus phases in a medium-voltage substation compartment?
A phase barrier, and its material depends on whether it also carries load. The arc-facing containment layer is inorganic mica (muscovite, then phlogopite for the hottest bands): non-carbonizing, dimensionally stable, and non-combustible.
Where the barrier is a structural phase separator, standoff, or baffle, it is glass-epoxy laminate (G10 / FR4, G11 for higher temperature) or Durostone composite, with a UL 94 class and an IEC 60112 CTI on the laminate TDS. The barrier-finder on this page assembles the shortlist; the compartment geometry and the CTI requirement fill in the numbers. [6]
Mica vs glass-fibre paper vs glass-epoxy: which barrier goes where?
By duty. Mica (muscovite / phlogopite) is the arc-facing containment layer: inorganic, non-carbonizing, to the compartment. ManniGlas-class glass-fibre paper is the non-combustible fire-side liner: it lines steel and layers into cable-penetration stacks, with UL 94 V-0 and ASTM C177 data per TDS. Glass-epoxy (G10 / FR4 / G11) and Durostone are the structural barriers that also carry load, with the CTI and dielectric on the laminate TDS.
Most compartment designs use two or three of these together; climb the inorganic temperature ladder only as far as the TDS band requires. [10]
What is a comparative tracking index (CTI), and when does it govern the barrier choice?
CTI (per IEC 60112) measures a material’s resistance to surface tracking — the carbonized conductive path that creeps across a contaminated surface. It governs whenever a barrier sits in a dusty or condensing compartment, because tracking arrives long before bulk dielectric puncture: a thick barrier with a low CTI still fails.
Call out the CTI requirement for those locations and choose a laminate or composite grade (Durostone, the glass-epoxy grades) whose TDS carries it, then pair it with dry-arc resistance (ASTM D495) where the surface also sees an arc. [6]
How do fire barriers work in a BESS, and what does NFPA 855 govern?
In a battery energy storage system, the barrier layers work at three scales: module-to-module and rack-to-rack barriers slow a thermal event between neighbors, enclosure fire-blocking layers keep it inside the unit, and cable-penetration barriers block propagation along the runs leaving the enclosure. The materials are the same inorganic families — ManniGlas-class glass-fibre paper, mica barrier sheet, mica containment sheet — to the module footprint.
NFPA 855 governs the installation: spacing, capacity limits, and the documentation the AHJ reviews. It is cited by designation; the barrier materials support a design evaluated to it, and the evaluation belongs to the tested system. [4]
What lines a cable penetration through a fire-rated wall?
A layered barrier stack: an inorganic non-combustible face and backing (ManniGlas-class glass-fibre paper, mica barrier sheet) block flame and heat propagation along the run. Where the penetration must also seal an expanding gap under fire, intumescent products are part of the firestop system, which is installed and tested at the assembly level.
H-O converts the inorganic barrier and backing layers of the stack, to the boundary, framed by designation; H-O does not certify a firestop system. Send the wall detail and the cable bundle, and engineering frames the layers and the standards language correctly. [4]
Why does the smoke number matter in an enclosed electrical room?
Because a material can hold a UL 94 flame class and still fill an enclosed room with dense smoke, which strands an occupied MCC or electrical room in an event. The flame class says nothing about smoke obscuration or toxicity; the FST data does — specific optical density of smoke (ASTM E662) and surface flammability under radiant heat (ASTM E162).
For an occupied room, put those on the callout and specify an FST-documented grade (FST neoprene, kSil® V-0 silicone sponge), or use inorganic families (mica, glass-fibre paper) that sidestep the smoke question by not burning. [11]
Is mica or glass-fibre paper the ceramic-free option?
ManniGlas-class glass-fibre paper is the ceramic-free non-combustible barrier paper: an inorganic glass-fibre construction, distinct from ceramic (RCF) papers, that lines steel and layers into penetration stacks with UL 94 V-0 file classes and ASTM C177 thermal data per TDS. Mica is a separate inorganic family used as the arc-containment face and high-temperature barrier.
Both are inorganic and non-combustible; where a design specifically calls for a ceramic-paper barrier, that duty sits in the same band, but the glass-fibre paper is the common ceramic-free choice. [10]
Does H-O extrude or mold these barriers, or convert them?
H-O die-cuts, waterjet-cuts, slits, and laminates sheet and roll stock to drawing; molding and extrusion are not done in our own plant, and molded or extruded profiles are coordinated through a partner network. Conversion runs in Winsted, Connecticut under an ISO 9001:2015 certified quality management system with material traceability and lot-code TDS records. Thick mica and composite plate is waterjet-cut; thin papers and films are and slit; barrier stacks are kitted in assembly order.
What is the difference between NFPA 70E and IEEE C37.20.7 here?
They live at different levels, and both are cited by designation. IEEE C37.20.7 (with IEC 62271-200) is the internal-arcing-fault test that qualifies arc-resistant switchgear as a complete assembly — it is where an arc rating for the equipment comes from. NFPA 70E is the workplace electrical-safety standard: it governs the arc-flash boundary, the PPE program, and the arc-rated clothing the worker wears, tested to ASTM F1959.
Neither is something a barrier material “meets”; the material supports the tested assembly and brings its own TDS classes, and the two standards frame the equipment qualification and the workplace program respectively. [3]
Can H-O supply a complete compartment barrier stack as a kit?
Yes: the mica containment face, the glass-epoxy or Durostone phase barrier, the glass-fibre paper liner, and any heat-shield gasket can ship as a kitted stack, cut to the compartment or penetration and stacked in assembly order, with a lot-code TDS record per material. That documentation is exactly what an assembly-level arc or fire qualification wants to see. Send the compartment or penetration detail with the duty and the standards language you need, and engineering frames the stack and the paperwork.
What should I put on the drawing so the quote comes back right the first time?
By duty: for an arc / phase barrier, the compartment geometry, whether it bears load, and any CTI requirement; for a compartment or penetration fire barrier, the boundary detail, the cable bundle, and the temperature band; for a BESS barrier, the module footprint and the NFPA 855 context; for an FST room, the enclosed-room smoke/toxicity requirement (ASTM E662 / E162).
Plus continuous vs. fault-event exposure, quantities for prototype and production, and the standards language you need on the paperwork (material classes per TDS; assembly and installation standards by designation). “Recommend the barrier” is a valid callout: that is what the material review is for.
Glossary: terms used on this page
Quick reference for the arc, fire, and barrier terminology used throughout. Each entry links to the relevant standard or test method where applicable.
Arc rating (belongs to the assembly / PPE)
A measure of arc-flash protection (cal/cm²; ATPV or EBT) that belongs to arc-resistant switchgear qualified as a complete assembly per IEEE C37.20.7 [1], or to an arc-rated PPE garment/program tested to ASTM F1959 in the NFPA 70E context. It is never a property of a barrier material; the material supports a tested design and brings its own TDS classes.
IEEE C37.20.7 (by designation)
The guide for testing metal-enclosed switchgear for internal arcing faults, per [1]. Arc-resistant switchgear is qualified as a complete assembly (accessibility types 1 / 2 / 2B). Barrier materials are ingredients of that qualification, never holders of its result; cited on this page by designation.
IEC 62271-200 (by designation)
The standard for AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV, including internal arc-fault classification (IAC classes). Like IEEE C37.20.7, it qualifies the tested assembly; the barrier materials support the design and are cited here by designation.
NFPA 70E (by designation)
The standard for electrical safety in the workplace: the arc-flash boundary, the risk assessment, and the arc-rated PPE program (clothing tested to ASTM F1959). It governs the workplace and the worker’s protection, not a barrier material; cited here by designation as the safety context for electrical rooms. See [3].
NFPA 855 (by designation)
The standard for the installation of stationary energy storage systems: spacing, capacity limits, and the documentation an AHJ reviews for a BESS. The installation tier that frames BESS fire barriers, cited here by designation. See [4].
FST (flame, smoke, toxicity)
The set of properties that governs materials in enclosed occupied spaces: flame spread, smoke obscuration (specific optical density per ASTM E662 [11]), and toxicity. A material can hold a UL 94 flame class and still fail on smoke; the FST data is a separate TDS line, and it governs the enclosed electrical-room callout.
Comparative tracking index (CTI)
A material’s resistance to surface tracking — a carbonized conductive path across a contaminated surface — measured per IEC 60112 [6]. It governs barrier selection in dusty or condensing compartments, where tracking fails a surface long before the bulk material punctures. Durostone and the glass-epoxy grades carry a CTI on their TDS.
Dry arc resistance (ASTM D495)
The high-voltage, low-current dry arc resistance of an insulating material, per ASTM D495 [7]: how long a surface withstands an arc before it becomes conductive. A material-level TDS property (heat-shield silicone foam and the laminates report it), distinct from an assembly arc rating.
Muscovite vs. phlogopite mica
Two mica chemistries used as inorganic barrier sheet. Muscovite is the general arc-containment and high-voltage barrier mica; phlogopite is the maker-designated higher-temperature step for the hottest bands. Both are inorganic, non-carbonizing, and non-combustible; order them qualitatively by the maker temperature designation, not by an invented degree limit.
G10 / FR4 / G11 (glass-epoxy laminate)
The industrial glass-fabric / epoxy laminate grades (NP500A / NP510A / NP511 designations) used as load-bearing phase barriers and baffles. FR4 adds a flame-retardant system with a UL 94 V-0 file class per TDS; G11 is the higher-temperature step. Rigid-laminate methods per IEC 60893 [8] / ASTM D229.
Glass-fibre barrier paper (ManniGlas-class)
An inorganic, ceramic-free glass-fibre barrier paper (grades in the 1200 / 1900 / 1902 / 2000 family) used as a non-combustible fire-side liner and cable-penetration layer. Grades carry UL 94 V-0 file classes and thermal-conductivity data per ASTM C177 [10] on the maker TDS.
Durostone composite
A glass-reinforced composite laminate (UPM 203 / UPM S16 designations) used for arc-resistant structural isolation and phase barriers where the highest tracking resistance and mechanical strength are wanted together. UL 94 V-0 file class and IEC 60112 CTI on the TDS.
Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
Standards, test methods & technical references
The standards, test methods, and maker technical data sheets cited throughout this page. Assembly and installation standards are cited by designation: they qualify assemblies, govern installations, and frame the workplace, and the rating belongs to the tested design. Standards editions current as of July 2026; verify against the publishing body before final spec. H-O materials are aligned to these standards through the source manufacturer’s TDS, not independently certified by H-O unless explicitly stated on the quote.
[1] IEEE C37.20.7 (by designation)
IEEE Guide for Testing Switchgear Rated Up to 52 kV for Internal Arcing Faults. The assembly-level internal-arcing-fault test that qualifies arc-resistant switchgear (accessibility types 1 / 2 / 2B). Cited by designation; the arc rating belongs to the tested assembly. standards.ieee.org (C37.20.7)
[2] IEC 62271-200 (by designation)
High-voltage switchgear and controlgear — AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV, including internal arc classification (IAC). Cited by designation; qualifies the tested assembly. webstore.iec.ch (62271-200)
[3] NFPA 70E (by designation)
Standard for Electrical Safety in the Workplace. Governs the arc-flash boundary, the risk assessment, and the arc-rated PPE program in electrical rooms. Cited by designation as workplace-safety context; it governs the worker’s protection, not a barrier material. nfpa.org (NFPA 70E)
[4] NFPA 855 (by designation)
Standard for the Installation of Stationary Energy Storage Systems. Governs BESS spacing, capacity limits, and the documentation an AHJ reviews. Cited by designation as installation context for BESS fire barriers. nfpa.org (NFPA 855)
[5] UL 94
Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances (HB, V-2, V-1, V-0 classes). A material-level flammability class per each grade’s TDS, grade-specific and not family-wide. shopulstandards.com (UL 94)
[6] IEC 60112 (comparative tracking index)
Method for the determination of the proof and the comparative tracking indices of solid insulating materials (CTI). The surface-tracking-resistance line on the laminate and composite TDS; governs barrier selection in contaminated compartments. webstore.iec.ch (IEC 60112)
[7] ASTM D495 (dry arc resistance)
Standard Test Method for High-Voltage, Low-Current, Dry Arc Resistance of Solid Electrical Insulation. A material-level surface-arc-withstand property on the heat-shield foam and laminate TDS, distinct from an assembly arc rating. astm.org (D495)
[8] ASTM D229 / IEC 60893 (rigid laminate methods)
ASTM D229 (methods of testing rigid sheet and plate materials used for electrical insulation) and IEC 60893 (industrial rigid laminated sheets based on thermosetting resins, incl. the G10 / FR4 / G11 grade families). The qualification methods behind the glass-epoxy and composite grades. webstore.iec.ch (IEC 60893)
[9] Mica laminate sheet TDS (muscovite / phlogopite)
Manufacturer technical data sheets for muscovite and phlogopite mica laminate sheet (rigid and flexible grades): inorganic, non-carbonizing barrier mica with UL 94, dielectric, and thermal data by grade. Values per the TDS on file; verify the grade band against the source sheet. cogebi.com (mica laminates)
[10] ASTM C177 & ManniGlas-class glass-fibre paper TDS
ASTM C177 (steady-state heat flux / thermal-conductivity by the guarded-hot-plate method) and the glass-fibre barrier-paper (ManniGlas-class, grades 1200 / 1900 / 1902 / 2000) technical data sheets carrying UL 94 V-0 file classes and C177 thermal data. Values per the TDS on file. astm.org (C177)
[11] ASTM E662 (specific optical density of smoke) & FST neoprene TDS
ASTM E662 (specific optical density of smoke generated by solid materials) and the low smoke / low flame / low toxicity (FST) neoprene technical data sheets carrying UL 94 V-0 with E662 smoke data. The smoke line that governs enclosed occupied rooms. Values per the TDS on file. astm.org (E662)
[12] ASTM E162 (radiant surface flammability) & kSil V-0 sponge TDS
ASTM E162 (surface flammability of materials using a radiant heat energy source) and the kSil® V-0 silicone-sponge technical data sheets reporting E162 / E662 on the super-soft grade. The radiant-flame companion to the smoke line for enclosed rooms. Values per the TDS on file. astm.org (E162)
[13] IEC 60243 / ASTM D149 (dielectric strength)
IEC 60243 (electric strength of insulating materials) and ASTM D149 (dielectric breakdown voltage and dielectric strength of solid electrical insulating materials). The bulk-breakdown line on the laminate, paper, and foam TDS; paired with CTI for barriers in contaminated compartments. astm.org (D149)
Updated . Standards editions and links current at publication; verify against the publishing body before final spec. H-O materials are “aligned to” the standards cited through the source manufacturer’s TDS; H-O does not certify systems or assemblies, and does not independently certify materials unless explicitly stated on the quote. Lot-specific qualification documentation available on request.
To review your barrier design, send:
- The duty (arc-side / fire-side / FST-room)
- Structural role (load-bearing plate or lining)
- Compartment, penetration, or module geometry (DXF / STEP / PDF)
- Continuous vs. fault-event exposure
- Any UL 94 class, CTI, or FST requirement from the spec
- Temperature band or hot-adjacent surfaces
- Standards language needed on the paperwork
- Prototype and annual volume
Get an arc-and-fire barrier engineering quote
Send a drawing set, a compartment or penetration detail, or a barrier spec. We typically respond within one business day with a barrier-material recommendation, prototype lead time, and TDS verification against your duty, temperature band, tracking, and standards language.
See also: related H-O application pages
Engineering content for the adjacent energy sub-applications and the parent hub. Each page covers material selection, failure modes, and converter-side process detail for its application family.
Sibling sub-application
Power distribution & electrical insulation
The dielectric-barrier and creepage playbook behind this page’s phase-barrier laminates and mica: films, papers, and laminates across the voltage range.
Read the page
Sibling sub-application
Outdoor power & substation sealing
The weather and ingress side of the same substation enclosures: die-cut gaskets and seals for outdoor power equipment.
Read the page
Sibling sub-application
Nuclear & SMR
High-integrity barrier and sealing materials for small modular reactor and nuclear electrical systems, with the documentation trail those programs demand.
Read the page
Industry hub
Energy, power & renewable
The full energy application family: insulation, EMI, thermal, arc-and-fire, sealing, vibration, solar, hydrogen, and nuclear infrastructure.
Read the page
Material data & standards. All flammability, tracking, dielectric, smoke, and thermal values on this page are taken from the source maker’s technical data sheets with the method named (UL 94; IEC 60112 CTI; IEC 60243 / ASTM D149; ASTM D495; ASTM E662; ASTM E162; ASTM C177; ASTM D229 / IEC 60893).
Assembly and installation standards (IEEE C37.20.7, IEC 62271-200, NFPA 70E, NFPA 855) are cited by designation only: they qualify assemblies, govern installations, and frame the workplace, the rating belongs to the tested design, and the barrier materials on this page support a design evaluated to them. An arc rating (cal/cm²) is never a property of a material.
H-O converts materials; H-O does not design switchgear or battery systems, does not certify assemblies or firestop systems, and does not independently certify materials against the standards unless explicitly stated on the quote. Verify against the maker TDS and your assembly-level qualification plan.
Conversion scope. H-O and converts sheet, roll, and blanket stock to drawing in Winsted, Connecticut: die-cut and kiss-cut barriers and gaskets, slit papers and films, waterjet-cut thick mica and composite plate, laminations, and kitted barrier stacks, with material traceability and lot-code TDS records. H-O does not mold or extrude in its own plant; molded or extruded profiles are coordinated through a partner network. Lead-time and MOQ details are in the process strip and the quote form above.