Data Center Indoor Sealing & Airflow Management
H-O Products die-cuts and converts aisle-containment strips, rack blanking and bypass-airflow gaskets, raised-floor grommets and cutout seals, CRAC/CRAH unit gasketing, intake-filtration foams, and top-of-rack cable-pass seals into the airflow-sealing material set inside the data hall, built to your drawing.
Built for: hot-aisle and cold-aisle containment systems, 19-inch and OCP rack platforms, raised-floor plenums, CRAC/CRAH and fan-wall cooling units, and the white-space details whose airflow design is commonly framed by ASHRAE TC 9.9 thermal guidelines at the facility level.
To seal a data hall against bypass airflow, work the six leak paths in order of size. Aisle containment: close panel-to-panel, panel-to-rack, and door-perimeter gaps with RE-series EPDM foam strips (compression classes per ASTM D1056 on the grade TDSs) or BISCO® HT-870-class cellular silicone where a flame class or temperature endurance drives the choice. Rack blanking: gasket blanking panels and rail edges with PORON® 4701-series microcellular urethane (methods per ASTM D3574.
The remaining zones and duties are mapped in the When-to-spec list on this page. Values are per the TDS on file.
Facility-level, by designation (the airflow and fire-protection design belongs to the facility engineer): ASHRAE TC 9.9 thermal guidelines for data processing environments · NFPA 75 (fire protection of information technology equipment). Material-level, per the vendor TDS: UL 94 (flammability classes, incl.
V-0 on the rated grades) · ASTM D1056 (cellular rubber compression classes: EPDM, neoprene, vinyl nitrile) · ASTM D3574 (flexible cellular polyurethane methods: PORON®, filter foam) · ASTM E84 (surface burning characteristics, where reported per grade).
- Containment panel & door strips: RE-series EPDM foam / BISCO® HT-870
- Blanking-panel gaskets: PORON® 4701 series (40V0 for V-0 duty)
- Floor-cutout grommets: vinyl nitrile foam + EPDM sponge
- CRAC/CRAH frame gaskets: RE42E EPDM / SCE42B neoprene
- Intake filtration: reticulated filter foam by PPI
- Low-closure-force joints: BISCO® BF-1000 Extra Soft
- Cable-pass wipe seals: F-1 / F-10 pressed felt
Where are you in the spec process?
This page serves engineers who already know the gasket or strip they want and engineers still walking the white space hunting for the leaks. Pick the path that matches where you are; you don't have to read the rest.
Send a drawing, get a quote
A blanking-panel gasket, an aisle-containment strip set, a raised-floor grommet, a CRAC frame gasket, a filter-foam insert, or a complete die-cut airflow-sealing kit on your drawing.
Skip to the quote form →Walk the six leak paths job by job
Six numbered jobs (aisle, rack, floor, cooling unit, vent and filter, cable pass), a leak-path checklist builder, and seven material families with TDS-cited methods and by-designation standards language.
Start with job 1 →
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1Send drawingUpload a DXF, STEP, or PDF, or describe the panel, rack, cutout, or unit. A sample part works too.
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2Material reviewEngineering reviews gap ranges, closure forces, and any flame-class requirement against the vendor TDSs, and frames the standards language correctly: material classes (UL 94) per TDS, facility frameworks (ASHRAE TC 9.9, NFPA 75) by designation.
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3PrototypeSamples typically ship in 3–5 business days for common 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, CNC knife cutting for kiss-cut gasket sets, slitting for strip stock, and kitting for per-rack and per-aisle material kits. Ongoing parts run with material traceability and lot-code TDS records.
Which leak path are you closing?
The six sealing and airflow jobs, zone by zone
Pick a zone to see the job, the materials that lead it, and what to put on the drawing.
Hot/cold-aisle containment strips & panel seals
Aisle containment turns a room-scale mixing problem into a duct-scale sealing problem: once the cold aisle is boxed in, every unsealed joint in the box is a calibrated leak. The big panels come from the containment-system maker; the material that decides whether the system performs is the compressible layer at every interface, panel to panel, panel to rack top, door perimeter, roof deck to building structure, and the end-of-row transitions where containment meets columns and cable tray.
Those gaps are irregular, the closure forces are light, and the parts are long, thin, and cut to fit, which is exactly the converter's side of the job.
What H-O converts. Die-cut and slit gasket strips, D-section pads, and corner pieces from RE-series EPDM foam (RE41E through the firmer grades, compression classes per ASTM D1056 on the grade TDSs), EPDM sponge, and BISCO® HT-870-class cellular silicone where the spec calls for silicone-class temperature endurance or a specific flame class (UL 94 listings per the individual grade TDSs).
For very light closure forces, doors that must latch with fingertip effort, BISCO® BF-1000 Extra Soft conforms at pressures stiffer foams ignore. Where a drawing calls for brush or pile strip at sliding doors, H-O supplies the foam and felt sealing set around it and can coordinate extruded or woven strip hardware through a partner network.
Material guidance. EPDM foam is the economical default for indoor containment: closed-cell, dimensionally stable, and available in compression classes that match light panel loads. Cellular silicone earns its premium where the design brief names a flame class on the gasket itself or where panels sit close to warm exhaust air for years. Final material selection should be validated in the application; performance depends on grade, geometry, compression, adhesive system, and environment.
Panel and door drawings with gap ranges (nominal and worst case), strip cross-section or gap-fill target, lengths and quantities per aisle, any flame-class requirement on the material, and whether the strips mount mechanically or with adhesive backing.
Rack blanking & bypass-airflow gaskets
An unblanked U-space is a short circuit: hot exhaust air recirculates through the empty slot to the equipment intakes above it, and the inlet temperature the servers report stops matching the supply air the cooling plant produces. Blanking panels close the slot, but a hard panel against a hard rail still leaks around its perimeter, through rail slots, and down the gap between mounting rail and cabinet side. The gasket layer is what turns a blanking panel from a visual fix into an airflow fix.
What H-O converts. Kiss-cut blanking-panel perimeter gaskets, rail-edge strips, and side-channel air dams from PORON® 4701-series microcellular urethane (methods per ASTM D3574 on the TDS; low compression set keeps a thin gasket sealing through years of panel swaps), with PORON® 4701-40V0 where the location demands a UL 94 V-0 class on the gasket itself. Wider rail-to-side gaps take RE-series EPDM foam or vinyl nitrile foam blocks. Parts ship kiss-cut on liner, in per-rack kit counts, through CNC knife cutting and kitting.
On adhesive backing. Most blanking and rail gaskets mount with a pressure-sensitive adhesive, and most rack steel is powder-coated, a lower-surface-energy finish than bare metal. Adhesive-backed gasket performance depends on the substrate, its surface energy and preparation, temperature, exposure, dwell time, applied pressure, joint geometry, and assembly method; the adhesive system should be validated on the actual painted panel before the kit is released.
H-O laminates the PSA grade your validation selects and documents it per the adhesive vendor's TDS.
Panel and rail drawings (or the rack maker and model), gasket footprint and thickness, compressed-gap range, per-rack quantities, the PSA requirement if any, and any flame-class callout. A sample panel is the fastest path to a validated PSA recommendation.
Raised-floor grommets & cutout seals
A raised-floor plenum is a pressure vessel with hundreds of intentional openings (the perforated tiles) and, in most legacy halls, hundreds of unintentional ones: cable cutouts under every cabinet, openings at PDUs, and gaps where tiles meet columns and ramps. Every unsealed cutout bleeds static pressure the perforated tiles were sized to use, so the fan plant works harder to hold setpoint at the far end of the room. Sealing the cutouts is the cheapest static-pressure recovery available in an operating hall, and it is a materials job.
What H-O converts. Split grommet pads, brush-alternative wipe layers, and cutout collars from SBE41VN/SBE42VN vinyl nitrile foam and the ENSOLITE® IG1 family, which conform around irregular cable bundles at low closure force; tile-perimeter and PDU-base seals from EPDM sponge; and layered felt wipe seals from F-1 and F-10 SAE pressed felt where cables move during adds and changes. Thick sections cut clean on waterjet; production strips run on flatbed dies.
Material guidance. The floor grommet's job is conforming, not clamping: pick the softest closed-cell grade that recovers after every re-entry into the cutout, with compression behavior per ASTM D1056 on the grade TDS. Split designs that open around an existing bundle retrofit without re-pulling cable. May be suitable as a retrofit program across an operating hall, one cabinet row at a time; final selection should be validated in the application.
Cutout dimensions and locations, typical cable-bundle diameter range, tile thickness, plenum static-pressure target if known, quantities by cutout size, and whether the grommet must be re-enterable for future cable adds.
CRAC/CRAH unit gasketing
The cooling unit is where the whole room's airflow gets paid for, and its own sheet metal is a leak path: frame joints, access panels and doors, the plenum collar where the unit meets the raised floor or duct, and the filter rack whose gasket decides whether air goes through the filter media or around it. A CRAC/CRAH that leaks at the filter rack reports clean filters and delivers dusty air; one that leaks at the plenum collar short-circuits its own supply.
What H-O converts. Frame and access-panel gaskets from RE41E/RE42E EPDM foam (compression classes per ASTM D1056 on the TDSs) and SCE42B-class neoprene foam; filter-rack channel seals cut to the rack extrusion; plenum-collar gaskets in wide frames or four-piece sets; and condenser-side or reheat-adjacent gaskets in BISCO® cellular silicone where panel temperatures near reheat coils or fan motors run beyond comfortable EPDM duty for years at a time (grade temperature ranges per the vendor TDS).
Unit-base vibration pads and the acoustic side of fan-wall duty live on the NVH sibling pages; this page carries the air-sealing layer.
Material guidance. Cooling-unit gaskets are classic enclosure work: match the foam's compression class to the real closure force of the panel fastener pattern, and let any flame-class or temperature requirement pick between the EPDM and silicone tracks before cost does. Commonly specified with PSA backing for service-friendly panel work; the adhesive-validation framing from job 2 applies here unchanged.
Unit maker and model or panel drawings, gasket cross-sections and lengths, filter-rack extrusion profile, closure forces or fastener patterns, temperature at the gasket location, and service quantities if this is a maintenance program rather than OEM build.
Pressure-equalization vents & intake filtration
Not every opening should be sealed. Contained aisles and sealed equipment galleries need engineered relief paths so door swings, fan staging, and maintenance events don't load the containment panels; and equipment intakes inside the hall, PDU vents, in-row cooler faces, network-gear filters, still want a dust barrier even in a filtered room. Both jobs belong to the same converted-material family: open-cell reticulated foam that passes air on purpose, framed by gaskets that stop the air everywhere else.
What H-O converts. Die-cut reticulated polyurethane filter foam inserts and panels, selected by PPI (pores per inch) grade against the airflow and dust-holding requirement, with frames and perimeter gaskets from RE-series EPDM or silicone foam so the filtered path is the only path. Washable filter-foam inserts are a common service item: kiss-cut sets, bagged per unit, through kitting.
The deep version of this material logic, vent membranes, PPI selection, dust-holding versus pressure-drop trade-offs, lives on the filtration & venting application page; this section is its white-space edition.
Material guidance. Coarser PPI grades trade dust capture for lower pressure drop; finer grades reverse the trade. Specify the airflow per opening and the acceptable pressure drop, and let the PPI grade fall out of those two numbers per the foam vendor's data. Flame-class requirements on filter media are per the vendor TDS, by grade designation only.
Opening dimensions, airflow per opening (CFM) and allowable pressure drop if known, dust environment, washable-versus-disposable preference, frame or retention detail, and quantities per unit and per site.
Top-of-rack cable-pass seals
Containment ceilings and top-of-rack panels are full of openings that exist for good reason: fiber trunks, power whips, and copper bundles have to cross the boundary. Each pass-through is a small bypass leak that multiplies by every rack in the row, and unlike the raised-floor version, these openings change constantly as circuits are added. The sealing part has to admit a cable today and still seal tomorrow.
What H-O converts. Kiss-cut, slit-to-open foam blocks and layered wipe seals that close around bundles and re-close after moves: vinyl nitrile foam and ENSOLITE®-family blocks for conformable fill, F-1/F-10 pressed wool felt leaf seals where cables slide through repeatedly, and PORON® perimeter gaskets on the pass-through plate itself (the 4701-40V0 grade where a UL 94 V-0 class is called out, per its TDS). Multi-layer cross-slit designs, two or three offset slit layers, seal around mixed bundle sizes without custom holes per circuit.
Material guidance. Re-enterability is the controlling property: open-celled or very soft grades that take a compression set after the first bundle stop sealing on the second. Closed-cell vinyl nitrile and pressed felt both recover well in this duty; compression behavior per ASTM D1056 (cellular grades) and felt classes per the SAE felt designations on the vendor TDS. Final selection should be validated in the application.
Opening sizes and counts, bundle diameter range and mix, expected re-entry frequency, plate or frame detail, and whether the seal mounts to the rack top, the containment ceiling, or both.
Where conditioned air escapes: the six leak paths
A representative cross-section of a contained cold aisle. Numbered callouts mark the six leak paths this page seals; the numbers match the job sections above. Representative line-art diagram, not a product photo or an engineering drawing.
Representative cross-section for orientation only. Geometry, airflow direction, and unit placement vary by facility; the leak paths do not.
The decisions that drive a data-center sealing & airflow spec
Airflow parts are chosen by the leak they close and the fire class the room demands — in that order.
Name the leak path first, then match the material to the closure force and the fire class the room requires. Foams carry their own flame and compression class per grade TDS.
Show all 5 selection factors tap to expand
Airflow-sealing failures you can prevent at spec
White-space sealing fails quietly: nothing trips, nothing alarms, the hall just runs warmer and the fans run harder. Four patterns cover most of what we see, and each is a specification decision made before the first part is cut.
Bypass losses hide in plain sight. A hall can pass commissioning with every big panel in place and still leak through a hundred small joints nobody drew a gasket for. The fix is cheap at drawing time and tedious afterward.
Show all 4 failure modes tap to expand
1. The containment system that sealed on day one and leaked by year two
Containment strips picked by thickness alone take a compression set under sustained panel load, and the gap they filled at commissioning reopens as the foam relaxes.
The leak is distributed and invisible: no single joint looks bad, but supply temperature drifts up. The fix: specify the gap range and the closure force, then pick the grade whose compression-deflection data (per ASTM D1056 on the TDS) holds that window with margin, and weight compression-set behavior as heavily as initial fit. Soft, recoverable grades outlast firm ones in lightly loaded joints.
2. Blanking gaskets whose adhesive let go of the powder coat
A PSA that gripped the sample bar in the office releases from textured powder coat in the hot aisle, and the gaskets end up on the floor behind the row. Powder coatings are commonly low-surface-energy finishes, and hot-aisle temperatures accelerate whatever the bond line was going to do anyway. The fix: validate the adhesive system on the actual painted panel, at the actual temperature, with the dwell and pressure the installers will really apply.
Adhesive performance depends on substrate, surface energy, temperature, exposure, dwell, pressure, surface preparation, and joint geometry; the validation belongs in the program plan, and the panel sample belongs in the RFQ package.
3. The floor grommet that sealed once
An open-cell or over-soft cutout seal conforms beautifully around the first cable bundle, then tears or sets when the bundle is re-pulled during a circuit add, and the cutout stops sealing for good. Multiply by every cabinet in a hall with monthly adds and the plenum bleeds from a hundred old wounds. The fix: treat re-enterability as the controlling property.
Closed-cell vinyl nitrile and layered felt wipe designs recover through repeated entries; split and cross-slit geometries let the part open without being destroyed. State the expected re-entry frequency on the drawing and the geometry follows.
4. The filter that filtered nothing
A filter-rack gasket that leaks turns the filter into decoration: air takes the quarter-turn path around the media, the filter stays suspiciously clean, and the coil fouls instead. The same logic applies to retrofit filter-foam inserts cut loose enough to bow out of their frames. The fix: gasket the rack channel as carefully as the door, and dimension filter-foam inserts for a slight interference fit in the frame, with the PPI grade chosen against airflow and pressure-drop targets rather than whatever was in the parts bin.
The filtration logic lives on the filtration & venting page; the sealing logic is this page's job 4 and job 5.
Specification Tools
Two tools to take you from "the hall runs warm" to here's the sealing-part checklist for the drawing set: a leak-path checklist builder that assembles the part list with its material families, and a side-by-side comparison of every sealing family on this page.
1. White-space leak-path checklist builder
Check the leak paths your white space carries. The builder assembles the corresponding sealing parts into a checklist with the material family and what to send with the drawing. The default selection below is pre-built for a typical contained-aisle retrofit; every part is also printed in the material reference section, so nothing here exists only behind a script.
Sealing-part checklist: 3 parts selected
Each checked leak path adds its part below. The list is the starting bill of materials for the engineering review, not a performance claim: material classes (UL 94) come from the grade TDS, facility frameworks (ASHRAE TC 9.9, NFPA 75) are cited by designation, and final material selection should be validated in the application.
- Containment strips: RE-series EPDM foam (BISCO® silicone for flame-class duty)Send: gap range, strip cross-section, lengths per aisle, mounting method. Cite: ASTM D1056 classes per the grade TDS.
- Blanking & rail gaskets: PORON® 4701 series (4701-40V0 for V-0 duty)Send: panel drawings, compressed-gap range, per-rack counts, PSA requirement. Cite: ASTM D3574 methods; UL 94 V-0 per the 40V0 TDS.
- Floor grommets: vinyl nitrile / ENSOLITE® foam, split or cross-slitSend: cutout sizes, bundle diameter range, re-entry frequency. Cite: ASTM D1056 classes per the grade TDS.
2. Bypass-airflow & containment-gap calculator
Estimate the open bypass area a rack and its tile are carrying, index how severe it is relative to the rack face and the engineered supply path, and read the sealing parts that close it. Adjust the three inputs; the containment diagram on the right shows the seal points and switches each from open to sealed as you act on them. Outputs are relative open-area and ratio figures for prioritization, not a CFM, energy, or PUE prediction; the facility engineer owns the airflow design.
Sealing parts for this case
Representative layout — not to scale. Geometry, airflow direction, and unit placement vary by facility; the seal points do not. Markers 1–6 key to the six sealing jobs above.
How the numbers are computed (worked example & assumptions)
Open areas. Each unblanked U exposes 1.752 in × 17.75 in ≈ 31.1 in² of the rack face (the EIA-310 U height by the clear opening width at the 19″ rail face). Rack open area = Uopen × 31.1 in²; total open bypass area = rack open + open floor-cutout area.
Bypass index. A dimensionless ratio: index = (total open bypass area ÷ full rack-face area) × pressure weight, where rack-face area = rack U × 31.1 in² and the pressure weight is 0.85 / 1.00 / 1.20 for low / typical / high supply-to-return bias. An index of 1.00 means the open bypass area equals the entire rack face; 0 means nothing is open. The secondary readout compares the same open area to one supply tile’s engineered open area (24×24 in at ~25% open = 144 in²) — the plenum-pressure framing.
Worked example. 10 open U, a 72 in² floor cutout, a 42U rack, typical pressure:
- Rack open =
10 × 31.1 = 311 in² - Total open bypass =
311 + 72 = 383 in²(2.66 ft²) - Rack face =
42 × 31.1 = 1306 in² - Index =
(383 ÷ 1306) × 1.00 = 0.29→ Moderate bypass - Secondary =
383 ÷ 144 = 2.7×one supply tile’s open area - Blank all 10 U and grommet the cutout → open bypass → 0 in² = 100% of the open bypass area removed (index → 0.00). Blanking only the U-spaces removes 81%.
This is a prioritization aid, not an airflow model. It sizes and ranks open area, the quantity sealing parts act on directly; it does not predict CFM, temperature, fan power, or PUE, which depend on the cooling architecture, load, and controls the facility engineer owns. Constants are nominal EIA-310 / tile geometry; substitute your measured opening widths and tile open-area fraction for a site-specific figure.
3. Side-by-side: airflow-sealing 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 property | Standards on the TDS / by designation | Job on this page | |
|---|---|---|---|---|---|
| Gasket & strip families | |||||
| RE-Series EPDM Foam (RE41E/RE42E) + 553/EPDM spongeClosed-cell EPDM | Closed-cell foam | Compression class vs panel load | ASTM D1056 (per grade TDS) | Containment strips; CRAC frames | |
| PORON® 4701 Series + 4701-40V0Microcellular urethane | Microcellular PU foam | Compression-set resistance | ASTM D3574; UL 94 V-0 (40V0 TDS) | Blanking & rail gaskets; pass-through plates | |
| BISCO® Cellular Silicone (HT-870 Soft, BF-1000 Extra Soft, RS-800 Medium)Cellular silicone | Silicone foam/sponge | Flame class / temp endurance | UL 94 listings per grade TDS; ASTM E162/E662 where reported | Flame-class strips; reheat-adjacent gaskets | |
| Vinyl Nitrile Foam (SBE41VN/SBE42VN, ENSOLITE® IG1)Closed-cell VN | Closed-cell VN foam | Conformability + recovery | ASTM D1056 (per grade TDS) | Floor grommets; cable-pass blocks | |
| Neoprene Foam (SCE42B class)Closed-cell CR | Closed-cell neoprene | Compression class; oil tolerance | ASTM D1056 (per grade TDS) | CRAC/CRAH panel & collar gaskets | |
| Airflow-management & wipe families | |||||
| Reticulated Polyurethane Filter FoamOpen-cell PU, by PPI | Open-cell reticulated PU | PPI vs pressure drop | ASTM D3574 methods; flame data per grade TDS | Intake filtration; vents | |
| Pressed Wool Felt (F-1, F-10 SAE classes)SAE pressed felt | Compressed wool felt | Wipe duty + re-entry recovery | SAE felt class designations (per vendor TDS) | Cable-pass wipe seals; floor cutouts | |
| Silicone Foam (frame & vent gaskets)Cellular silicone sheet | Silicone foam sheet | Temperature range per TDS | UL 94 listings per grade TDS | Vent-frame & filter-frame gaskets | |
Skip ahead and request your engineering review now
If your drawing set already calls out a foam grade, a strip cross-section, a grommet geometry, or a filter-foam PPI, send it over for engineering review against the vendor TDSs and the standards language.
Material reference
Detailed specs for the seven airflow-sealing families referenced on this page: the gasket and strip set (RE-series EPDM foam, PORON® microcellular urethane, BISCO® cellular silicone, vinyl nitrile, neoprene foam) and the airflow-management set (reticulated filter foam, pressed wool felt). Values are per the vendor TDS on file for each grade with the method named; facility frameworks are cited by designation only. H-O die-cuts, kiss-cuts, slits, and kits every family to drawing.
RE-Series EPDM Foam (RE41E / RE42E) + EPDM SpongeContainment strips & cooling-unit gaskets · ASTM D1056 compression classes per grade TDS
Specify the gap range and closure force, not just thickness; the compression class falls out of those two numbers per the ASTM D1056 data on the grade TDS.
PORON® Industrial Microcellular Urethane (4701 Series, 4701-40V0)Blanking-panel & rail gaskets · ASTM D3574 methods · V-0 class on the 40V0 TDS
Most of these parts ship PSA-backed onto powder-coated steel. Adhesive performance depends on substrate, surface energy, temperature, exposure, dwell, pressure, surface preparation, and joint geometry; validate the adhesive system on the actual panel.
BISCO® Cellular Silicone (HT-870 Soft, BF-1000 Extra Soft, RS-800 Medium)Flame-class strips & warm-zone gaskets · UL 94 listings per the grade TDSs
Often specified when a facility's materials list applies a single flame-class rule to every polymer in the room; the per-grade UL 94 listings on the TDSs are the documentation that review wants to see.
Vinyl Nitrile Foam (SBE41VN / SBE42VN, ENSOLITE® IG1)Floor grommets & cable-pass blocks · ASTM D1056 classes per grade TDS
State the re-entry frequency on the drawing: it drives both the grade and the slit geometry.
Neoprene Foam (SCE42B Class)CRAC/CRAH panel & plenum-collar gaskets · ASTM D1056 classes per grade TDS
For genuinely fluid-exposed gasket duty (oils, refrigerant-loop service), the chemical and fluid sealing pages carry the deeper material logic; this page's neoprene parts are air-side gaskets first.
Reticulated Polyurethane Filter Foam (by PPI grade)Intake filtration & vent inserts · ASTM D3574 methods · PPI per vendor data
The full PPI-selection and vent-membrane logic lives on the filtration & venting application page.
Pressed Wool Felt (F-1 / F-10 SAE Classes)Cable-pass wipe seals & floor-cutout leaf seals · SAE felt designations per vendor TDS
Felt is the quiet veteran of this page: the same SAE classes that wipe machine ways have closed cable openings for decades.
Data-center sealing & airflow materials: engineer-grade FAQ
Ten of the questions we hear most from containment, rack, and cooling-unit teams. If your question isn't here, send a drawing or call, engineering picks up.
Do airflow-sealing materials carry data-center listings?
There is no material-level data-center listing to claim. What a gasket or strip carries is its own documentation: UL 94 flammability classes on the rated grades per the vendor TDS, ASTM D1056 or D3574 method data behind its properties, and lot-code traceability. Facility frameworks, ASHRAE TC 9.9 thermal guidelines for the airflow design and NFPA 75 for fire protection of IT spaces, are cited by designation: they frame the facility engineer's design, and the materials on this page support designs commonly framed by them.
H-O's own certification is ISO 9001:2015, covering the quality system the parts are made under.
What is bypass airflow, and why is it a gasket problem?
Bypass airflow is conditioned air that returns to the cooling unit without passing through equipment, and recirculation is its mirror image: hot exhaust that finds its way back to an equipment intake. Both are geometry problems: air takes whatever opening is cheapest, and a data hall offers it unblanked U-spaces, unsealed floor cutouts, containment seams, and leaky unit panels. Each path is closed by a compressible converted part, a gasket, strip, grommet, or block, which is why a thermal problem ends up on a die-cutter's drawing.
What foam should go on rack blanking panels?
Commonly a thin PORON® 4701-series microcellular urethane gasket: the family's compression-set resistance keeps a 1–3 mm perimeter gasket sealing through years of panel swaps, with methods per ASTM D3574 on the TDS, and the 4701-40V0 grade carries a UL 94 V-0 class per its TDS where the location demands one. Wider rail-to-side gaps move to RE-series EPDM or vinyl nitrile blocks. Specify the compressed-gap range, not just thickness, and validate the PSA on the actual painted panel.
Do containment strips and blanking gaskets need a flame rating?
That decision belongs to the facility's materials rules, often written in the shadow of NFPA 75, which is cited here by designation as the fire-protection context for IT spaces. Many programs apply a flame-class requirement to every polymer in the white space; when yours does, materials are available with UL 94 V-0 ratings per the vendor TDS, PORON® 4701-40V0 on the urethane side and the BISCO® RS-series sponge grades on the silicone side carry per-grade listings.
The class belongs to the material grade per its TDS; H-O converts the listed grade and supplies its documentation.
EPDM or silicone for CRAC/CRAH gaskets?
RE-series EPDM foam is the economical default for indoor unit gaskets, with compression classes per ASTM D1056 on the grade TDSs. Move to BISCO® cellular silicone when a flame class is named on the gasket itself or when the joint sits warm for years, near reheat coils or fan motors, where silicone's temperature endurance (grade ranges per the vendor TDS) earns its premium.
Neoprene foam (SCE42B class) is the middle path where panel gaskets occasionally meet lubricants or condensate-pan cleaners. Match the compression class to the real closure force either way.
What seals a raised-floor cable cutout, and can it retrofit without re-pulling cables?
A split or cross-slit grommet pad of closed-cell vinyl nitrile foam (SBE41VN/SBE42VN or the ENSOLITE® IG1 family) that opens around the existing bundle, closes behind it, and recovers after future re-entries, with layered pressed-felt wipe seals where cables move often. Split designs retrofit an operating hall one cabinet row at a time without touching the cabling. Send cutout sizes, bundle diameter ranges, and the expected re-entry frequency; the geometry follows from those three numbers.
Can H-O supply brush seals for doors and cable openings?
H-O converts sheet, roll, and blanket stock: the foam blocks, layered felt leaf seals, and perimeter gaskets that do the same job as brush strip in many geometries, and frequently do it better at re-entry. Where a drawing specifically calls for extruded or woven brush-strip hardware, H-O can coordinate it through a partner network and supply the converted sealing set around it, kitted per opening through our assembly and kitting capability.
Will adhesive-backed gaskets stick to powder-coated rack panels?
Only if the adhesive system is chosen for the finish: powder coatings are commonly low-surface-energy substrates, and a PSA that grips bare metal may release from textured paint, especially at hot-aisle temperatures.
Adhesive performance depends on the substrate, its surface energy and preparation, temperature, exposure, dwell time, applied pressure, joint geometry, and assembly method, so the adhesive system should be validated on the actual painted panel before the kit is released. Send a sample panel with the RFQ; H-O laminates the PSA grade your validation selects and documents it per the adhesive vendor's TDS.
Does sealing the white space actually save cooling energy?
Reducing bypass and recirculation is one of the commonly reported levers for raising supply-air setpoints and reducing fan energy, which is why airflow management features in ASHRAE TC 9.9-framed design practice. How much any given hall recovers depends on its layout, cooling architecture, load, and controls; no gasket vendor can promise a number, and this page doesn't. What the materials do is mechanical and verifiable: close the measured leak paths so the airflow follows the engineered design, and let the facility's own monitoring report the result.
What should I put in the RFQ so the quote comes back right the first time?
By job: for containment, gap ranges, strip cross-sections, lengths per aisle, and mounting method; for blanking, panel drawings, compressed-gap range, per-rack counts, and the PSA requirement; for the floor, cutout sizes, bundle diameters, and re-entry frequency; for cooling units, the unit model or panel drawings, closure forces, and gasket temperature; for filtration, airflow per opening and allowable pressure drop.
Plus quantities for prototype and production and any flame-class callout with its location. "Recommend the material" is a valid callout: that is what the engineering review is for.
Glossary: terms used on this page
Quick reference for the airflow, containment, and materials terminology used throughout. Each entry links to the relevant standard or test method where applicable.
Bypass airflow
Conditioned supply air that returns to the cooling unit without passing through IT equipment, through unsealed cutouts, seams, and openings. The quantity every part on this page exists to reduce.
Recirculation
Hot exhaust air that re-enters an equipment intake instead of returning to the cooling unit, classically through unblanked U-spaces and over containment boundaries. The reason inlet temperatures stop matching supply temperatures.
Hot-aisle / cold-aisle containment
Physically enclosing one aisle of a rack row so supply and return air streams cannot mix: doors at the ends, panels or curtains overhead. Containment converts mixing losses into a finite set of sealable joints, which is where this page's strips and gaskets live.
Blanking panel
A filler panel that closes an unused rack U-space so exhaust air cannot short-circuit through the empty slot. Effective only with a gasketed perimeter; a hard panel on a hard rail still leaks around its edges.
Raised-floor plenum
The pressurized space under a raised floor used to distribute supply air to perforated tiles. Its working asset is static pressure, which every unsealed cable cutout bleeds away.
Static pressure
The pressure differential between plenum and room that drives airflow through perforated tiles. When it sags from leakage, far-end tiles starve and fans work harder to compensate.
CRAC vs CRAH
Computer Room Air Conditioner (direct-expansion refrigeration on board) versus Computer Room Air Handler (chilled-water coil). Mechanically different, identically gasketed: frame joints, access panels, plenum collars, and filter racks.
Delta-T (ΔT)
The temperature rise across equipment (or drop across a cooling unit). Bypass air collapses the return-side delta-T, a classic field signature that conditioned air is escaping around the load instead of through it.
ASHRAE TC 9.9 (by designation)
The ASHRAE technical committee whose thermal guidelines for data processing environments frame allowable and recommended equipment-inlet conditions, per [1]. Cited here by designation as design context; the airflow design belongs to the facility engineer.
NFPA 75 (by designation)
The standard for the fire protection of information technology equipment and spaces, per [2]. The context behind many facilities' materials rules; cited by designation only, and the fire-protection design belongs to the facility engineer.
ASTM D1056 class
The classification system for flexible cellular rubbers (EPDM, neoprene, vinyl nitrile), grouping grades by compression-deflection range per [3]. The number that matches a foam to a panel's real closure force.
Compression set
Permanent deformation after sustained compression: the property that decides whether a containment strip still fills its gap in year five. Reported per the cellular methods (ASTM D1056 [3], D3574 [4]) on the grade TDSs.
PPI (pores per inch)
The cell-count grading of reticulated filter foam. Coarser PPI passes more air with less dust capture; finer PPI reverses the trade. Selected against airflow and pressure-drop targets per the foam vendor's data.
Kiss-cut
Die-cutting through the material but not its release liner, so installers peel parts one at a time in sequence. The standard delivery format for PSA-backed blanking and rail gasket kits.
Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
Standards, test methods & technical references
The standards, guidelines, and vendor technical data sheets cited throughout this page. Facility frameworks are cited by designation: they frame the facility design, and the evaluation belongs to the facility engineer. 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 vendor's TDS; H-O does not certify systems or independently certify materials.
[1] ASHRAE TC 9.9 thermal guidelines (by designation)
ASHRAE Technical Committee 9.9, Thermal Guidelines for Data Processing Environments: the framework behind equipment-inlet temperature and humidity envelopes and the airflow-management practice this page's parts serve. Published by ASHRAE; cited by designation as design context only.
[2] NFPA 75 (by designation)
Standard for the Fire Protection of Information Technology Equipment, published by the National Fire Protection Association. The context behind many facilities' white-space materials rules; cited by designation only, with the fire-protection design belonging to the facility engineer and the AHJ.
[3] ASTM D1056
Standard Specification for Flexible Cellular Materials — Sponge or Expanded Rubber, published by ASTM International. The classification and method framework behind the EPDM, neoprene, and vinyl nitrile compression classes cited on the grade TDSs.
[4] ASTM D3574
Standard Test Methods for Flexible Cellular Materials — Slab, Bonded, and Molded Urethane Foams, published by ASTM International. The method set behind PORON® and reticulated-filter-foam property data on the vendor TDSs.
[5] UL 94 (classes per grade TDS)
Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances, published by UL. Flammability classes (including V-0) belong to the listed material grades per their vendor TDSs; this page cites them only where the grade's own TDS reports them.
[6] ASTM E84
Standard Test Method for Surface Burning Characteristics of Building Materials, published by ASTM International. Referenced where individual grade TDSs report surface-burning data; cited at the material level only.
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 airflow-sealing materials engineering quote
Send a drawing set, panel sample, or site sketch. We typically respond within one business day with a material recommendation, prototype lead time, and TDS verification against your gap ranges, closure forces, and any flame-class callouts.
See also: related H-O application pages
Engineering content for the adjacent data-center sub-applications, the parent sealing application, and the owning industry hub. Each page covers material selection, failure modes, and converter-side process detail for its application family.
Material data & standards. All compression, temperature, and flame-class values on this page are taken from the source vendor's technical data sheets with the method named (ASTM D1056, D3574, E84; UL 94 classes per the listed grade TDSs). Facility frameworks (ASHRAE TC 9.9 thermal guidelines, NFPA 75) are cited by designation only: they frame the facility design, the evaluation belongs to the facility engineer and the AHJ, and the materials on this page support designs commonly framed by them.
H-O converts materials; H-O does not design airflow systems, model plenums, or certify systems, and does not independently certify materials against the standards cited. Performance depends on grade, geometry, compression, adhesive system, and environment; final material selection should be validated in the application against the vendor TDS.
Conversion scope. H-O and converts sheet, roll, and blanket stock to drawing in Winsted, Connecticut: die-cut and kiss-cut gaskets, strips, and grommets, slit strip stock, waterjet-cut thick sections, laminations, and kitted per-rack and per-aisle sets, with material traceability and lot-code TDS records. H-O does not mold or extrude in-house; molded, extruded, or brush-strip hardware is coordinated through a partner network. Lead-time and MOQ details are in the process strip and the quote form above.