HVAC Fire & High-Temperature Protection
H-O Products die-cuts and converts the fire and heat-side material set inside gas-fired and high-temperature HVAC equipment: furnace and burner-compartment gaskets, fire-barrier die-cuts, flue and exhaust interface seals, high-temperature wire and harness protection, smoke-damper seals, and combustion-blower gaskets, cut to your drawing from glass-fiber paper, mica sheet, cellular and solid silicones, coated-fiberglass fabrics, and aerogel blanket.
Built for: residential and commercial furnaces, rooftop units with gas heat sections, boilers and unit heaters, smoke and combination dampers, and the burner-adjacent compartments where the drawing has to separate a flame zone from sheet metal, wiring, and everything downstream, with appliance and damper standards (ANSI Z21.47/CSA 2.3, UL 555/555S, NFPA 90A) cited by designation at the equipment level.
To spec fire and high-temperature materials in HVAC equipment, work from the flame outward and let the temperature band pick the family.
Burner and furnace compartments: BISCO® HT-series cellular silicone door and access-panel gaskets (TDS service ranges on the order of -55 to +200 °C per the maker data), stepping to ManniGlas® glass-fiber paper at the hot walls; the 1200 grade reports handling to 1200 °F (640 °C) without shrinkage and a UL 94 V-0 class per its TDS.
Fire-barrier die-cuts: ManniGlas®, mica barrier sheet (muscovite, then phlogopite where the maker's temperature designations demand more headroom), BISCO® RF-120 heat-shield silicone foam beside hot zones, and ArmaGel® HT aerogel blanket (ASTM C177 conductivity and E84 surface-burning data per TDS).
Flue and exhaust interfaces: mica and glass-fiber gaskets on the hot side; solid silicone collar and condensate-side seals at lower flue temperatures per the grade TDS. Harness protection: die-cut and slit wraps of PTFE-coated fiberglass, Kapton® HN film, and Nomex® aramid paper.
Smoke dampers: silicone sponge with UL 94 listings per the grade TDSs and FST-rated neoprene with ASTM E662 smoke data per TDS; UL 555/555S belong to the damper maker's tested assembly, by designation. Combustion blowers: FR silicone sponge and solid silicone flange gaskets sized to the bolt pattern.
Appliance and system standards are cited by designation only; final material selection should be validated in the application. Skip to the quote form →
Equipment-level, by designation (the listing belongs to the maker's tested assembly): ANSI Z21.47 / CSA 2.3 (gas-fired central furnaces) · UL 555 (fire dampers) · UL 555S (smoke dampers) · NFPA 90A (installation of air-conditioning and ventilating systems).
Material-level, per the maker TDS with the method named: UL 94 (flammability classes on the listed grades) · ASTM E84 / UL 723 (surface burning characteristics) · ASTM E662 / E162 (smoke density and radiant-panel flame spread) · ASTM C177 / C518 (thermal conductivity) · ASTM D1056 / D3574 (cellular methods).
- Burner-compartment gaskets: BISCO® HT silicone foam / solid silicone
- Hot-wall barrier paper: ManniGlas® 1200 / ManniGlas® series
- Highest-temperature barrier: phlogopite mica / muscovite mica
- Radiant-heat shield by hot zones: BISCO® RF-120
- Thinnest insulation per mm: ArmaGel® HT aerogel
- Flame-class gasket callouts: BISCO® RS-series sponge / kSil® KSV001–KSV006 V-0 sponge
- Harness wrap (hot, abrasive): PTFE-coated fiberglass
- Harness wrap (thin, dielectric): Kapton® HN / Nomex® paper
- Smoke-sensitive seals: FST neoprene (E662 per TDS)
- Combustion-blower flanges: RS-800 Medium / solid silicone
Where are you in the spec process?
This page serves engineers who already know the fire layer or gasket they need and engineers still mapping the heat side of the equipment job by job. Pick the path that matches where you are; you don't have to read the rest.
Send a drawing, get a quote
A ManniGlas® or mica barrier, a BISCO® HT or RS-series gasket, a solid silicone flue seal, a kiss-cut harness-wrap kit, or a complete burner-compartment material set on your drawing.
Skip to the quote form →Walk the equipment job by job
Six numbered jobs (burner compartment, fire barriers, flue interfaces, harness protection, smoke dampers, combustion blowers), a checklist-driven layer builder, and eight material families with TDS-cited methods and by-designation standards language.
Start at the burner compartment →
Where H-O parts do the work
Pick a job to see the exposure, the constraint, and the material families H-O converts for it.
Furnace & burner-compartment gaskets
Every gas-fired furnace, RTU heat section, and unit heater has a compartment whose gaskets work harder than the rest of the cabinet combined: the burner and heat-exchanger enclosure. Its access panels and burner-box covers have to seal combustion air paths, keep flue products on their side of the wall, and do it across thousands of firing cycles that swing the sheet metal from room temperature to its working band and back.
The appliance itself is evaluated at the equipment level (ANSI Z21.47 / CSA 2.3 for gas-fired central furnaces, by designation; the listing belongs to the appliance maker's tested assembly); the converter-side contribution is a gasket set whose temperature rating, compression behavior, and flame-class documentation match what the design review asks for.
What H-O converts. Die-cut burner-box cover gaskets with bolt patterns in place, access-panel perimeter gaskets, sight-glass and igniter-port seals, and strip gaskets for heat-exchanger cell dividers. BISCO® HT-series cellular silicone (HT-800 Medium through HT-870 Soft) carries the panel and cover joints, with TDS service ranges on the order of -55 to +200 °C per the maker data and ASTM D1056 cellular classes per the grade TDSs.
Solid silicone sheet (30–70 durometer commercial grades) takes the bolted flanges where a sponge would extrude, with TDS service temperatures on the order of -80 to +450 °F per the grade data. Where the joint sits against the hot wall itself, the gasket stops being an elastomer problem: ManniGlas® glass-fiber paper takes over, with the 1200 grade reporting handling to 1200 °F (640 °C) without shrinkage per its TDS.
Material guidance. Pick the family by the joint's real temperature band, not the compartment's nameplate: a door gasket two sheet-metal layers away from the flame sees a fraction of the heat-exchanger surface temperature, and over-speccing every joint to the hottest number in the cabinet buys cost without function. Often specified: HT-series silicone foam on doors and covers; solid silicone at bolted, hotter flanges; glass-fiber paper at the hot wall.
Where gaskets ship with pressure-sensitive adhesive for assembly, adhesive performance depends on substrate, surface energy, temperature, environmental exposure, dwell time, applied pressure, surface preparation, part geometry, and the assembly process; final adhesive selection should be validated in the application, and burner-adjacent PSA placements deserve a temperature check against the adhesive TDS, not just the foam TDS.
Grade-level properties, standards and caveats for these families are in the material reference below — one card per family, with the TDS links.
What to send: compartment and panel drawings with the joint locations marked, the measured or estimated temperature at each joint (not just the nameplate), available closure force, and any flame-class callout the design review requires on the gasket itself.
Fire-barrier for cabinets & compartments
Between the heat section and the rest of the unit sits a layer problem: blower compartments, control boards, refrigerant lines, and insulation foams all live one panel away from a flame zone, and the panel alone is rarely the whole answer. Fire-barrier are the converter-side ingredient: inorganic and flame-class-documented layers that slow radiant and conducted heat, resist ignition, and give the equipment designer the documented materials a design review wants to see.
The barrier strategy is evaluated on the appliance maker's tested assembly; the materials carry their own classes per TDS, which is the language this page uses throughout.
What H-O converts. Die-cut barrier panels, baffles, and shields in four constructions, ordered by where they work. ManniGlas® glass-fiber paper (1200, 1900-series grades) is the workhorse inorganic barrier: thin, die-cuttable, dimensionally stable at burner-adjacent temperatures per the grade TDSs, with ASTM C177 thermal data and UL 94 V-0 classes on the rated grades. Mica barrier sheet steps in above it: muscovite grades for most flame-adjacent duty, phlogopite where the maker's temperature designations demand more headroom.
BISCO® RF-120 heat-shield silicone foam shields components beside hot zones, combining a radiant-heat-facing construction with gasket-like conformability per its TDS. ArmaGel® HT aerogel blanket buys the most temperature drop per millimeter where space is tight, with thermal conductivity per ASTM C177 and surface burning per ASTM E84 on the TDS.
Material guidance. Decide what each barrier is for before picking it: ignition resistance (the layer must not become fuel), radiant shielding (the layer must reflect or absorb without passing heat), or insulation (the layer must slow conduction). Glass-fiber paper and mica answer the first two; aerogel answers the third; RF-120 splits the difference beside hot zones.
Flame-spread and smoke-developed indices (ASTM E84 / UL 723) and UL 94 classes belong to the listed grades per their TDSs, and NFPA 90A frames the duct-and-plenum materials context by designation at the installation level.
The deeper barrier-layering logic, which face takes the flame, which takes the insulation, travels well from the battery world; see the thermal-runaway fire protection sibling for the layered version of the same thinking.
Grade-level properties, standards and caveats for these families are in the material reference below — one card per family, with the TDS links.
What to send: the compartment layout with the hot surface and the protected component both dimensioned, the temperature at the barrier plane if you have it, the space available for the layer, and the documentation the design review requires (UL 94 class, E84 indices, or both, per TDS).
Flue & exhaust interface seals
The flue path is two sealing problems wearing one name. On the hot side, the heat-exchanger outlet, flue collector box, and vent connector flanges run at temperatures that retire elastomers, and their gaskets are inorganic: mica and glass-fiber constructions that stay dimensionally stable and do not contribute fuel. On the cool side, condensing appliances pull flue gases low enough that the problem inverts: the seal faces acidic condensate and modest temperatures, which is elastomer territory, solid silicone collars and grommets sized to the vent pipe.
Getting the two sides confused is the classic flue-gasket misspecification, in both directions.
What H-O converts. Die-cut collector-box and flue-flange gaskets in mica sheet (muscovite for most flue flanges, phlogopite per the maker's temperature designations where the design needs more headroom) and ManniGlas® glass-fiber paper, with bolt patterns and breakout tabs cut to the drawing rather than field-trimmed. For condensing and lower-temperature vent interfaces: solid silicone collar seals, vent-pipe grommets, and condensate-side gaskets from commercial-grade silicone sheet, with service temperatures and compression data per the grade TDSs.
Laminated constructions, glass-fiber paper faced with foil or film where the design calls for a gas-side facing, run through in-house lamination; thick inorganic stacks cut clean on waterjet.
Material guidance. Specify the flue-gas temperature at the joint and whether condensate reaches it; those two numbers sort the family. Gas-tightness in these joints comes from flange flatness, fastener pattern, and gasket compression working together, so send the joint, not just the gasket outline. Refrigerant and oil exposure elsewhere in the unit is a different chemistry conversation, with compatibility per vendor TDS compatibility tables, covered under the chemical, oil & fluid sealing sibling page.
Grade-level properties, standards and caveats for these families are in the material reference below — one card per family, with the TDS links.
What to send: the flue-gas temperature at each sealed joint, condensing or non-condensing duty, flange drawings with bolt patterns, and the vent-pipe diameters for collars and grommets. Appliance venting requirements stay with the appliance maker's tested design, by designation.
High-temperature wire & harness protection
Igniter leads, flame-sensor wires, limit-switch harnesses, and blower power runs all have one thing in common: somewhere between the control board and their device, they pass close to surfaces that would cook their primary insulation. The materials job is a protective layer between conductor and heat: wraps, sleeking liners, shields, and grommet-edged pass-throughs that hold their properties at the local temperature and document it per the maker TDS.
It is a small-parts category with outsized warranty consequences, because a harness that chafes or embrittles next to a heat exchanger fails years before the equipment around it.
What H-O converts. Slit and wrap stock, kiss-cut shield sets on liner, and pass-through pieces in three constructions split by mechanics. PTFE-coated fiberglass fabric carries the hot-and-abrasive duty: a woven glass core for temperature and a PTFE face for slip and release, slit to wrap widths or to shield outlines, with grade data per the maker TDS.
Kapton® HN polyimide film is the thin dielectric layer where the harness needs an electrical barrier as well as a thermal one, to board-adjacent shields and wrapped barriers (gauges per the maker designations).
Nomex® aramid paper takes the conformable middle: tougher than film, more formable than laminate, the classic motor-lead and junction-area insulation per the 410/414 grade TDSs. Mica and ManniGlas® pieces back up the set where a pass-through sits directly against the hot wall.
Material guidance. Specify the local temperature at the harness path and the failure you are designing against: abrasion against vibrating sheet metal wants the coated-fabric face, dielectric spacing wants film or paper, and direct hot-wall contact wants the inorganics. These are converted flat goods, wraps, shields, and barriers, not extruded sleeving; where the design calls for molded or extruded sleeve product, H-O coordinates through a partner network and supplies the balance of the kit.
Wraps that close with PSA carry the standard caveat: adhesive performance depends on substrate, surface energy, temperature, exposure, dwell time, pressure, surface preparation, geometry, and assembly process; validate the adhesive in the application at the local temperature.
Grade-level properties, standards and caveats for these families are in the material reference below — one card per family, with the TDS links.
What to send: the harness routing with hot surfaces dimensioned, local temperatures where known, the failure mode you are protecting against (abrasion, embrittlement, dielectric), and whether you want slit wrap stock, kiss-cut shield kits, or both. The electrical-insulation side of the same panels lives on the energy, power & high voltage application family.
Smoke-damper & combination-damper seals
Smoke and combination fire/smoke dampers are evaluated as assemblies, UL 555 for fire dampers and UL 555S for smoke dampers, by designation, with the listing belonging to the damper maker's tested assembly, and NFPA 90A framing where they sit in the duct system.
Inside that tested assembly are converter-side parts: blade-edge seals, frame and jamb gaskets, and actuator-compartment seals whose job is to limit leakage at the damper's rated pressure and temperature class while contributing as little smoke and flame as possible if the day ever comes.
The damper maker owns the evaluation; the seal materials carry their own documented classes per TDS.
What H-O converts. Die-cut and slit blade-edge seals, frame perimeter gaskets, jamb strips, and actuator-housing gaskets. Silicone is the default chemistry for the temperature classes dampers carry: BISCO® RS-series FR silicone sponge (RS-800 Medium and siblings) where the design wants cellular conformability with UL 94 listings per the individual grade TDSs, kSil® KSV001–KSV006 V-0 sponge in the same FR sponge family, and solid silicone strip where the blade edge needs a wiping seal rather than a crush seal.
Where the smoke side of the specification dominates, FST-rated low smoke / low flame / low toxicity neoprene brings ASTM E662 smoke-density and E162 radiant-panel data on its TDS, the documentation smoke-sensitive air-path designs ask for.
Material guidance. Match the seal material to the damper's temperature class and the leakage class the maker is testing to, and put the documentation requirement on the drawing: a UL 94 class, E662 smoke data, or both, per TDS. Blade seals see motion; specify the cycle count and whether the seal wipes or compresses, because compression set (per ASTM D1056 on the grade TDSs) decides whether a crush seal still seals after years in the open position.
The general damper-and-duct gasketing playbook, flange gaskets, plenum seals, access doors, lives with the engineered sealing & gasketing application family; this job is its fire-and-smoke edition.
Grade-level properties, standards and caveats for these families are in the material reference below — one card per family, with the TDS links.
What to send: the damper's temperature and leakage class targets, blade and frame drawings, cycle expectations, and the documentation the test plan requires on each material (UL 94, E662/E162, D1056 class, per TDS). UL 555/555S evaluation stays with the damper maker's tested assembly.
Combustion-blower & draft-inducer gaskets
The draft inducer is the hardest-working gasket cluster in a condensing furnace: a motorized blower bolted to the collector box, pulling combustion products through the heat exchanger and pushing them out the vent. Its gaskets seal warm, moisture-laden, mildly acidic flue gas at the inducer inlet flange, the housing halves, and the outlet-to-vent transition, while riding the blower's own vibration.
Leakage here is not a comfort problem; it puts flue products on the wrong side of the wall and trips pressure switches that take the appliance offline, which is why inducer gaskets are a disproportionate share of HVAC field-failure part numbers.
What H-O converts. Die-cut inducer-flange gaskets with bolt patterns and pilot holes in place, housing perimeter gaskets, outlet transition seals, and anti-vibration mounting pads under the blower feet. Silicone carries the duty: BISCO® RS-series FR sponge and the HT closed-cell series for conformable flange joints (D1056 classes per the grade TDSs), and solid silicone sheet at higher bolt loads, with service temperatures per the grade TDSs covering inducer-outlet conditions on condensing and mid-efficiency appliances.
Hotter, non-condensing collector interfaces step back to the inorganics from Job 3, glass-fiber paper and mica, when the local temperature retires elastomers. Blower-foot isolation pads tie into the wider vibration playbook under the NVH, shock & vibration control family.
Material guidance. Specify three numbers per joint: the local temperature, the bolt pattern and torque (which set the compression the gasket actually sees), and the condensate exposure. Sponge seals at low, even closure forces; solid silicone holds up under concentrated bolt loads; the inorganics take the joints beyond elastomer range. Compression set is the life-limiting property on a joint that thermal-cycles every firing sequence, so read the D1056 class and set data on the grade TDS rather than reusing a part number from a cooler appliance.
Final material selection should be validated in the application.
Grade-level properties, standards and caveats for these families are in the material reference below — one card per family, with the TDS links.
What to send: inducer and collector flange drawings with bolt patterns, local temperatures and condensing duty, blower mass for the isolation pads, and prototype plus production quantities. A sample of the current gasket works when drawings are scarce.
The decisions that drive a fire & high-temp seal spec
A fire and high-temperature seal is a short set of decisions made in order. Get the sequence right and the material follows.
Match the seal to the local temperature first, then to the documentation the design review asks for. The appliance’s fire and flue listings belong to the maker’s tested assembly (ANSI Z21.47 / CSA 2.3; dampers to UL 555S, NFPA 90A framing); H-O supplies seal materials that carry their own classes per grade TDS.
Show all 5 selection factors tap to expand
Specification Tools
Two tools to take you from "the heat section needs its material set" to here's the checklist for the drawing set: a requirement-driven layer builder that assembles the fire-and-heat checklist with its citations, and a side-by-side comparison of every family on this page.
1. Fire & high-temperature layer checklist builder
Check the jobs your equipment design carries. The builder assembles the corresponding material layers into a checklist with the family, what to send with the drawing, and the citation language (material classes per TDS; equipment standards by designation, listing with the maker's tested assembly). The default selection is pre-built for a typical gas-fired furnace or RTU heat section; every layer is also printed in the material reference section, so nothing here exists only behind a script.
Fire & heat checklist: 4 layers selected
Each checked job adds its layer below. The list is the starting bill of materials for the engineering review, not a certification: material classes (UL 94, E84 indices) come from the grade TDS, and equipment standards (ANSI Z21.47/CSA 2.3, UL 555/555S, NFPA 90A) are cited by designation with the listing belonging to the maker's tested assembly.
- Burner-compartment gaskets: BISCO® HT silicone / solid siliconeSend: joint drawings, local temperatures, closure force. Cite: ASTM D1056 classes; UL 94 per grade TDS.
- Fire barriers: ManniGlas® / mica / RF-120 / aerogelSend: compartment layout, barrier-plane temperature, space budget. Cite: UL 94 and E84 data per TDS.
- Flue seals: mica / glass-fiber hot side, solid silicone condensing sideSend: flue-gas temperature per joint, condensing duty, flange drawings. Cite: grade data per maker TDS.
- Blower gaskets: RS-series FR sponge / solid siliconeSend: flange drawings, bolt torque, condensate exposure. Cite: D1056 class and UL 94 per grade TDS.
2. Side-by-side: fire & high-temperature family comparison matrix
Every family called out on this page, with construction, the property that drives its selection, the standards its TDS cites, and the job it serves. Click a column header to sort. Click any material name to jump to its accordion entry.
| Material | Construction | Selection driver | Standards on the TDS / by designation | Equipment job | |
|---|---|---|---|---|---|
| Inorganic barriers (flame outward) | |||||
| ManniGlas® Glass-Fiber Paper (1200, 1900 series)Inorganic glass paper | Glass-fiber paper sheet | Hot-wall stability per TDS | UL 94 V-0 (1200 TDS); ASTM C177 | Hot walls, barriers, flue gaskets | |
| Mica Barrier Sheet (Muscovite / Phlogopite)Mica laminate | Inorganic mica sheet | Highest temperature step | Per the maker's temperature designations | Flue flanges, hottest barriers | |
| ArmaGel® HT Aerogel BlanketSilica aerogel in fiber web | Aerogel blanket | Thermal resistance per mm | ASTM C177; E84 (per TDS) | Tight-space insulation layers | |
| Silicone gaskets & shields | |||||
| BISCO® HT-Series Cellular SiliconeClosed-cell silicone foam | Cellular silicone | Temperature endurance, conformability | ASTM D1056; UL 94 per grade TDS | Burner-compartment doors & covers | |
| BISCO® RF-120 Heat-Shield Silicone FoamHeat-shield construction | Shield-faced silicone foam | Radiant shielding beside hot zones | Construction and data per its TDS | Component shields | |
| BISCO® RS-Series FR Sponge + kSil® KSV V-0FR silicone sponge | Cellular silicone sponge | Flame class on the gasket itself | UL 94 listings per the individual grade TDSs | Damper & blower seals | |
| Solid Silicone Sheet (30–70 Durometer)Solid silicone rubber | Solid elastomer sheet | Bolt-load tolerance, wiping seals | Service temperatures per the grade TDSs | Flanges, collars, blade edges | |
| Films, fabrics & smoke-sensitive layers | |||||
| PTFE-Coated Fiberglass + Kapton® + Nomex®Harness layer set | Coated fabric / film / paper | Abrasion vs dielectric vs conformability | Per the maker TDSs by grade | Harness & wiring protection | |
| FST-Rated Neoprene (Low Smoke / Flame / Toxicity)FST elastomer | Closed-cell FST neoprene | Smoke & toxicity data on the TDS | ASTM E662 / E162 per its TDS | Smoke-sensitive air paths | |
Fire & high-temp seal failures you can prevent at spec
These failures show up late and expensive — after the appliance is built and firing. Every one is preventable in the material callout.
The appliance’s fire and flue ratings belong to the maker’s tested assembly. A converter-side seal that is under-rated for local temperature or flame class puts that listing at risk.
Show all 5 failure modes tap to expand
1. Elastomer specified on a flue or burner-box flange
Fix — use inorganic mica or MannIGlas® glass-fiber where flange temperatures retire elastomers; they stay dimensionally stable and do not contribute fuel.
2. Silicone on the wrong side of a condensing flue
Fix — on the acidic-condensate cool side, use solid silicone collars and grommets sized to the vent pipe; keep mica and glass-fiber for the hot, dry side.
3. Under-documented flame or smoke class
Fix — specify FST-rated (ASTM E662 / E162) or UL 94–listed grades per the grade TDS so the seal clears the design review, not just the bench.
4. Compression set on a sponge gasket at temperature
Fix — match sponge grade and closure force to the operating band (BISCO® RS / HT, D1056 class per TDS) so the seal holds after thermal cycling.
5. Field-trimmed inorganic gaskets
Fix — die-cut mica and glass-fiber to the drawing with bolt patterns and breakout tabs in place; field-trimming fractures mica and sheds dust.
Material reference
Detailed specs for the eight fire- and heat-side families referenced on this page: the inorganic barriers (ManniGlas® glass-fiber paper, mica sheet, aerogel blanket), the silicone gasket set (HT-series cellular silicone with the RF-120 heat shield, RS-series FR sponge with kSil® V-0, solid silicone sheet), and the films, fabrics, and smoke-sensitive layers (the coated-fiberglass / Kapton® / Nomex® harness set and FST-rated neoprene).
Values are per the maker TDS on file for each grade with the method named; equipment standards are cited by designation only, with the listing belonging to the maker's tested assembly. H-O die-cuts, kiss-cuts, slits, laminates, and kits every family to drawing.
ManniGlas® Glass-Fiber Paper (1200, 1900 Series)Hot-wall gaskets, fire barriers & flue liners · 1200 °F (640 °C) handling without shrinkage per the 1200 TDS
Often specified as the first inorganic step past silicone's range; the grade TDS carries the deciding temperature and flame data. Final material selection should be validated in the application.
Mica Barrier Sheet (Muscovite & Phlogopite)Flue flanges & the hottest barriers · grade selection per the maker's temperature designations
Mica is brittle in thin sheet; bolt patterns, tabs, and handling clearances belong on the drawing, not in field hands. Send the joint geometry and the local temperature.
BISCO® HT-Series Cellular Silicone + RF-120 Heat ShieldBurner-compartment gaskets & component shields · TDS service ranges on the order of -55 to +200 °C (HT family)
Where gaskets ship with PSA, adhesive performance depends on substrate, surface energy, temperature, exposure, dwell, pressure, surface preparation, geometry, and assembly process; validate the adhesive in the application at the joint's real temperature.
BISCO® RS-Series FR Silicone Sponge + kSil® KSV-Series V-0Damper & blower seals with flame-class callouts · UL 94 listings per the individual grade TDSs
Compression set decides whether a crush seal still seals after years in one position; read the D1056 class and set data on the grade TDS against the damper's cycle life.
Solid Silicone Rubber Sheet (30–70 Durometer)Bolted flanges, flue collars & wiping blade seals · service temperatures per the grade TDSs
Durometer is the working spec: softer grades conform at low torque, firmer grades survive concentrated loads. Send the bolt pattern and torque with the drawing.
Harness Layer Set: PTFE-Coated Fiberglass, Kapton® HN, Nomex® PaperWire & harness protection split by mechanics · abrasion / dielectric / conformability, per the maker TDSs
These are converted flat goods; molded or extruded sleeving is coordinated through a partner network, with the balance of the kit supplied from Winsted.
ArmaGel® HT Aerogel BlanketTight-space insulation layers · ASTM C177 conductivity & E84 surface burning per TDS
Often specified where 3–10 mm has to do the work of much thicker commodity insulation. Final material selection should be validated in the application.
FST-Rated Neoprene (Low Smoke / Low Flame / Low Toxicity)Smoke-sensitive air-path seals · ASTM E662 smoke-density & E162 data per its TDS
Specify the smoke and flame documentation requirement explicitly on the drawing; "FST" without numbers is a conversation, not a callout.
HVAC fire & high-temperature materials: engineer-grade FAQ
Nine of the questions we hear most from furnace, RTU, boiler, and damper teams. If your question isn't here, send a drawing or call, engineering picks up.
Are these materials listed to UL 555S or the furnace standards?
No individual material is: UL 555 and UL 555S evaluate the damper maker's tested assembly, and ANSI Z21.47/CSA 2.3 evaluate the appliance, so the listing belongs to that tested equipment, not to a layer inside it. What the materials on this page carry is their own documentation: UL 94 classes and E84/E662 data on the rated grade TDSs, named test methods behind their thermal and compression values, and lot-code traceability.
They support designs commonly evaluated to the equipment standards; H-O supplies the converted layers and the paperwork, and the equipment designer owns the evaluation. [3]
What gasket seals a furnace burner-compartment door?
Commonly BISCO® HT-series cellular silicone for doors and covers, with TDS service ranges on the order of -55 to +200 °C per the maker data and ASTM D1056 compression classes per the grade TDSs; solid silicone sheet at bolted flanges where sponge would extrude; and ManniGlas® glass-fiber paper at the hot wall itself. Pick by the joint's measured temperature, not the compartment's hottest number, and put any flame-class requirement on the drawing so the grade TDS can answer it. [7]
What goes between a burner compartment and the rest of the cabinet?
A barrier picked for its actual job. Ignition resistance and radiant shielding point to the inorganics: ManniGlas® glass-fiber paper (1200 °F / 640 °C handling without shrinkage and UL 94 V-0 per the 1200 grade TDS) and mica sheet above it. Conducted-heat insulation points to ArmaGel® HT aerogel blanket (ASTM C177 data per TDS). Components beside hot zones take BISCO® RF-120 heat-shield silicone foam. Many designs layer two: an inorganic flame face with an insulating tier behind it. [2]
Muscovite or phlogopite mica for flue and exhaust joints?
Muscovite carries most flue-flange and collector-box duty; phlogopite is the step up where the maker's temperature designations demand more headroom, typically the joints closest to the heat-exchanger outlet on non-condensing equipment. The practical answer comes from two numbers on your drawing: the flue-gas temperature at the joint and the flange's bolt pattern. On condensing appliances the cool-side joints often leave mica entirely and move to solid silicone collars, because the problem becomes condensate, not temperature. [1]
How do I protect wiring that runs near a heat exchanger?
Split the duty by the failure you are designing against. Abrasion against vibrating sheet metal wants PTFE-coated fiberglass fabric, slit to wrap widths or to shields. A thin layer that must also insulate electrically wants Kapton® HN polyimide film or Nomex® aramid paper, per the maker TDSs. Direct hot-wall contact at pass-throughs steps to mica or glass-fiber pieces. State the local temperature on the drawing; the harness path's hottest inch sets the family, and the TDS data answers at that temperature, not the nameplate.
What seal material suits a smoke-damper blade or frame?
Silicone in flame-rated grades is the default: BISCO® RS-series FR sponge or kSil® KSV-series V-0 sponge for crush seals (UL 94 listings per the individual grade TDSs), and solid silicone strip where the blade wipes. Where the smoke side of the specification dominates, FST-rated neoprene adds ASTM E662 smoke-density and E162 data on its TDS.
Match the material to the damper's temperature and leakage class targets, and remember the division of labor: the seal carries its material classes per TDS; UL 555/555S evaluation belongs to the damper maker's tested assembly. [3]
What gasket survives a draft inducer on a condensing furnace?
One that matches three numbers per joint: the local temperature, the bolt pattern and torque, and the condensate exposure. RS-series FR silicone sponge handles conformable flange joints at low, even closure forces; solid silicone sheet takes concentrated bolt loads and the outlet transition; hot-side collector interfaces beyond elastomer range step back to ManniGlas® or mica.
Compression set is the life-limiting property on a joint that thermal-cycles every firing sequence, so read the ASTM D1056 class and set data on the grade TDS rather than carrying over a part number from a cooler appliance. [7]
Does H-O test or certify fire performance?
No. H-O is an ISO 9001:2015 certified converter; that is the company's only certification, and it covers the quality management system, not fire performance. Flame, smoke, and temperature data come from the source maker's TDSs with the test methods named (UL 94 classes, ASTM E84/UL 723 indices, E662/E162 data), and equipment standards are cited by designation with the listing belonging to the maker's tested assembly.
What H-O adds is conversion to drawing, material traceability, and lot-code TDS records, the paperwork side of a fire-safety design review.
What should I send for a first quote on a fire and heat material set?
By job: joint drawings and local temperatures for the burner-compartment gaskets; the compartment layout, barrier-plane temperature, and space budget for the fire barriers; flue-gas temperatures and condensing duty for the flue seals; harness routing with hot surfaces dimensioned for the wiring protection; temperature and leakage class targets for the damper seals; and flange drawings with bolt torque for the blower gaskets.
Add prototype and production quantities and the documentation each material must carry (UL 94 class, E84 or E662 data, D1056 class, per TDS). "Recommend the stack" is a valid callout: that is what the engineering review is for.
How should high-temperature gaskets be attached — adhesive or mechanical?
It depends on the service temperature at the joint. Pressure-sensitive adhesives have their own temperature limits, typically well below those of the gasket materials on this page, so hot joints often rely on mechanical retention, with adhesive serving as an assembly aid rather than the working attachment. Adhesive limits are confirmed against the adhesive manufacturer’s data at material review.
Can I get material samples before committing to a design?
Yes — material swatches and cut samples are available on request, subject to material availability. For evaluation builds, the usual path is to send the part drawing so prototype parts are cut from the actual grade and thickness under consideration; that puts representative parts in your fixture instead of a generic swatch.
Are there minimum order quantities?
Minimums depend on the material and format rather than a single policy. Prototype quantities are quoted case-by-case, and production minimums are typically driven by the vendor’s sheet or roll purchase unit for the specific material. Stating your target annual volume on the RFQ lets H-O quote realistic break points up front.
Glossary: terms used on this page
Quick reference for the combustion, fire-class, and materials terminology used throughout. Each entry links to the relevant standard or test method where applicable.
UL 94 flame classes (per grade TDS)
The flammability classification for plastic and elastomer materials (V-0, V-1, HF-1, HBF and siblings), per [1]. A flame class belongs to the listed material grade per its TDS; materials are available with UL 94 V-0 ratings per vendor TDS where the design requires them, and the class travels with the grade, not the family.
Flame-spread & smoke-developed indices (ASTM E84 / UL 723)
The tunnel-test pair of numbers reported for surface burning characteristics, per [2]. Duct- and plenum-adjacent material conversations often start here; the indices live on the maker TDS for the tested grade.
UL 555 & UL 555S (by designation)
The standards for fire dampers and smoke dampers, per [3]. Both evaluate the damper maker's tested assembly, including its temperature and leakage classes; blade and frame seal materials are ingredients of that assembly and carry their own classes per TDS.
NFPA 90A (by designation)
The standard for the installation of air-conditioning and ventilating systems, per [4]: the installation-level context for duct materials, dampers, and plenum-adjacent layers. Cited here by designation as design context only.
ANSI Z21.47 / CSA 2.3 (by designation)
The gas-fired central furnace standard, per [5]: the equipment-level evaluation the appliance maker's tested assembly carries. The gaskets and barriers on this page support designs commonly evaluated to it; they do not inherit its listing.
FST (flame, smoke, toxicity)
The three-axis materials question for occupied-space and airstream applications: how a material burns, how much smoke it makes (ASTM E662 smoke density, per [8]), and what its combustion products carry. FST-rated neoprene grades report this data on their TDSs, which is what smoke-sensitive seal specifications ask for.
Glass-fiber paper (ManniGlas®)
Inorganic paper made of glass fiber: thin, die-cuttable, and dimensionally stable at burner-adjacent temperatures (the 1200 grade reports 1200 °F / 640 °C handling without shrinkage per its TDS, with ASTM C177 thermal data). The first step past elastomer range in most HVAC fire-barrier stacks.
Muscovite vs phlogopite mica
The two mica chemistries behind barrier-sheet grades: muscovite for most flame-adjacent duty, phlogopite where the maker's temperature designations demand more headroom. Both are inorganic, non-combustible, and to flange and barrier geometry; the grade designation on the maker TDS decides between them.
Heat-shield silicone foam (RF-120 class)
A shield-faced cellular silicone construction that protects components from radiant heat beside hot zones while conforming like a gasket. It splits the difference between an inorganic barrier and an elastomer seal; construction and data per its TDS.
Continuous vs intermittent service temperature
The two temperature numbers a TDS may report: what the material rides indefinitely and what it tolerates in excursions. Firing cycles make HVAC joints excursion-heavy, so read both numbers against the joint's measured profile, and resist speccing every joint to the cabinet's hottest point.
Compression set (ASTM D1056 / D3574)
Permanent deformation after sustained compression, per the cellular methods in [7]. The life-limiting property for gaskets that thermal-cycle every firing sequence and for damper crush seals that hold one position for years; the grade TDS carries the class and set data.
Draft inducer (combustion blower)
The motorized blower that pulls combustion products through the heat exchanger and pushes them to the vent, proving draft to the pressure switch on the way. Its flange and housing gaskets seal warm, moist, mildly acidic flue gas while riding the blower's vibration, which is why they fail more often than the metal around them.
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, by name and designation. Equipment standards evaluate the maker's tested assembly or installation; material methods live on the source maker's TDSs. Standards editions current as of June 2026; verify against the publishing body before final spec. H-O converts materials tested to the material-level methods on the source maker's TDS; H-O does not certify systems or independently certify materials unless explicitly stated on the quote.
[1] UL 94 (material classes per TDS)
Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances, published by UL Solutions. Flame classes (V-0 and siblings) belong to the listed material grades per their TDSs; materials are available with UL 94 V-0 ratings per vendor TDS where the design requires them.
[2] ASTM E84 / UL 723 (by designation)
Standard Test Method for Surface Burning Characteristics of Building Materials, published by ASTM International and UL Solutions respectively: the tunnel test behind flame-spread and smoke-developed indices reported on barrier and insulation TDSs.
[3] UL 555 / UL 555S (by designation)
Standard for Fire Dampers and Standard for Smoke Dampers, published by UL Solutions. Both evaluate the damper maker's tested assembly, including temperature and leakage classes; seal materials inside the assembly carry their own classes per TDS, and the listing belongs to the tested damper.
[4] NFPA 90A (by designation)
Standard for the Installation of Air-Conditioning and Ventilating Systems, published by the National Fire Protection Association: the installation-level context for duct materials, plenum-adjacent layers, and damper placement. Cited by designation as design context.
[5] ANSI Z21.47 / CSA 2.3 (by designation)
Standard for Gas-Fired Central Furnaces, published jointly under ANSI and CSA designations: the equipment-level standard gas furnace designs are evaluated to. The listing belongs to the appliance maker's tested assembly; the materials on this page are converter-side ingredients of such designs.
[6] ASTM C177 / C518
Standard Test Methods for Steady-State Heat Flux Measurements (guarded-hot-plate) and Steady-State Thermal Transmission Properties (heat-flow-meter), published by ASTM International: the methods behind the thermal-conductivity values on the aerogel and glass-fiber TDSs cited here.
[7] ASTM D1056 / D3574
Standard Specification for Flexible Cellular Materials (sponge or expanded rubber) and Standard Test Methods for Flexible Cellular Materials, published by ASTM International: the compression-class, set, and cellular methods on the silicone foam, sponge, and neoprene TDSs cited here.
[8] ASTM E662 / E162
Standard Test Method for Specific Optical Density of Smoke Generated by Solid Materials and Standard Test Method for Surface Flammability of Materials Using a Radiant Heat Energy Source, published by ASTM International: the smoke-density and radiant-panel methods behind the FST data on the rated neoprene and silicone TDSs.
Updated . Standards editions current at publication; verify against the publishing body before final spec. H-O converts materials tested to the methods cited; H-O does not certify systems. Lot-specific documentation available on request.
Get an HVAC fire & high-temperature materials quote
Send a drawing set, compartment layout, or flange spec. We typically respond within one business day with a material recommendation, prototype lead time, and TDS verification against your temperature bands, flame-class callouts, and standards language.
See also: related H-O application pages
Engineering content for the adjacent fire-protection and thermal sub-applications, the parent page, and the industry hub. Each page covers material selection, failure modes, and converter-side process detail for its application family.
Parent page
Arc flash & fire protection
The same barrier families (glass-epoxy, ManniGlas®, mica, heat-shield foam, FST neoprene) on their electrical-equipment side: arc chutes, phase barriers, and switchgear fire layers.
Read the page
Industry hub
Industrial HVAC
The full HVAC application family: sealing and venting, vibration and acoustics, thermal insulation, electrical insulation, and the fire-and-heat set this page covers.
Read the page
Sibling sub-application
Thermal runaway & fire protection
The layered fire-barrier playbook at battery scale: which face takes the flame, which takes the insulation, and how the tiers stack.
Read the page
Sibling sub-application
HVAC electrical insulation & EMI
Dielectric barriers and EMI parts for HVAC control boards, VFDs, and electrical panels.
Read the page
Sibling sub-application
Refrigerant, oil & coolant sealing
Chemically compatible gaskets and seals for refrigerant, oil, and coolant joints in HVAC systems.
Read the page
Sibling sub-application
Engine bay & nacelle thermal insulation
High-temperature insulation around combustion at aerospace intensity: the thermal-cycling failure modes this page's hot zones share.
Read the page
Application overview
Thermal management & insulation
The cross-industry thermal overview: insulation systems, TIMs, fire-barrier layers, and the converted-materials catalog behind this page's families.
Read the page
Material data & standards. All temperature, flame-class, smoke, compression, and thermal values on this page are taken from the source maker's technical data sheets with the method named (UL 94 classes per the listed grade TDSs; ASTM E84/UL 723, E662, E162, C177/C518, D1056, D3574).
Equipment standards (ANSI Z21.47/CSA 2.3, UL 555, UL 555S, NFPA 90A) are cited by designation only: they evaluate the equipment maker's tested assembly or installation, and the materials on this page support designs commonly evaluated to them.
Performance depends on grade, geometry, compression, adhesive system, and environment; H-O converts materials and does not design appliances, certify systems, or independently certify materials against the standards unless explicitly stated on the quote. Verify against the maker TDS and your equipment-level evaluation plan; final material selection should be validated in the application.
Conversion scope. H-O and converts sheet, roll, and blanket stock to drawing in Winsted, Connecticut: die-cut and kiss-cut gaskets, barriers, and shields, slit wrap stock, waterjet-cut thick and brittle sections, PSA and facing laminations, and kitted heat-section sets, with material traceability and lot-code TDS records. H-O does not mold or extrude in-house; molded or extruded profiles are coordinated through a partner network.
Lead-time and MOQ details are in the quote form above; samples typically ship in 3–5 business days and production runs about 2 weeks after drawing approval.