Aisle Containment in Data Centers

Applications and Use Cases

By B. Decker, Digital Content Specialist  |  Farco Plastics  |  Published: July 2025  •  13 min read

Aisle containment works. Separating hot exhaust air from cold supply air cuts the load on HVAC systems, keeps rack inlet temperatures consistent, and reduces the energy bill. That much is settled. The harder question is what the panels are made of. And whether anybody checked before the installation went in.

Most containment panel procurement decisions are driven by price and lead time. Fire rating and thermal performance get treated as checkboxes, if they get treated at all. That is fine until an authority having jurisdiction (AHJ) reviews the installation and starts asking for UL 94 documentation that does not exist, or until a fire safety audit turns up materials that should never have been in the building. At that point, the whole containment system comes out.

This guide covers the three materials Farco supplies for data center aisle containment, what the fire safety standards actually require, and where each material fits in a real installation, and where it does not.

Fire Safety Standards That Apply to Containment Panels

NFPA 75: What the Standard Actually Requires

NFPA 75, Standard for the Fire Protection of Information Technology Equipment (2024 edition) governs data center fire safety. Section 6.7 covers aisle containment systems. A few things in that section are worth knowing before you specify a panel.

First, section 6.7.3 sets the material floor: flame spread index of 50 or less, smoke-developed index of 450 or less, tested to ASTM E84 or UL 723. That is not Class A. Class A requires FSI ≤25. The NFPA 75 minimum sits between Class A and Class B. Many FR-grade polycarbonate panels clear Class A anyway, and most AHJs hold projects to Class A regardless of the code baseline. The point is to know what you are buying and to have the test certificate in hand before installation.

Second, containment creates a fire suppression problem. Any panel that improves thermal separation by physically enclosing an aisle is also a panel that can block sprinkler spray patterns and prevent gaseous suppression agents from reaching a fire. NFPA 75 section 6.7.7 requires that existing suppression and detection systems be evaluated and modified as needed wherever containment is installed.

If sprinkler coverage is obstructed, the system gets modified to comply with NFPA 13. If a gaseous suppression system cannot achieve its required agent concentration because containment is in the way, section 6.7.10 requires modification to fix that too.

There is an alternative path. Section 6.7.8.1 allows automatic panel-removal mechanisms in place of sprinkler system modification, but the conditions are specific: smoke detection must initiate removal before the suppression system fires, removal cannot compromise egress, releasing devices must be listed for the application, and every removable obstruction in the entire suppression zone must come out. All five conditions. Not some of them.

Third, section 6.4.1.3 prohibits exposed cellular plastics in ITE area construction. No exceptions.

UL 94: The Rating That Matters at the Panel Level

UL 94 tests how plastic materials behave when they catch fire. For containment panels, V-0 is the minimum you should accept. V-0 means the material self-extinguishes within 10 seconds and does not produce flaming drips. Flaming drips matter because they spread fire to the floor and to adjacent equipment. A V-2 material, which allows flaming drips, has no place in a data center containment system.

ASTM E84: Flame Spread and Smoke

ASTM E84 measures how fast flame travels across a material surface and how much smoke it generates. Class A means FSI ≤25 and smoke-developed index ≤450. Class B allows FSI up to 75. NFPA 75 section 6.7.3 requires FSI ≤50, which falls between those two classifications.

In practice, specify Class A. It exceeds the NFPA 75 minimum by a meaningful margin, most AHJs require it at the project level regardless of what the code floor says, and the better FR-grade polycarbonate panels hit it without special ordering. Confirm your AHJ's specific requirement, then get the ASTM E84 test certificate at the actual panel thickness you are installing before anything goes on a truck.

Multiwall Polycarbonate: The Containment Workhorse

How It Works

Multiwall polycarbonate is not a solid sheet. Two or more polycarbonate face layers are connected by internal ribs, leaving a series of enclosed air channels running through the thickness of the panel. Those channels are what make it useful for containment. Air does not conduct heat well, so the hollow structure slows thermal transfer between the hot and cold aisles. A solid sheet of the same thickness does not do that.

For most containment applications, 8mm and 10mm multiwall are the working thicknesses. They give you enough rigidity to span a standard aisle width without flex, enough insulation to matter thermally, and a weight that does not require heavy overhead hardware.

Industry estimates put cooling energy savings from multiwall polycarbonate containment at 20–25% by eliminating hot and cold air mixing. 

The FR Grade Distinction

Polycarbonate is self-extinguishing by nature: when ignited, it tends to melt back from the flame rather than feed it. That behavior is why FR-grade multiwall typically achieves ASTM E84 Class A at 6mm and 8mm thicknesses, exceeding what NFPA 75 section 6.7.3 actually requires. It also achieves UL 94 V-0 at those thicknesses.

The word "typically" is doing real work in that sentence. V-0 and Class A are not guaranteed properties of all polycarbonate. They are properties of FR-grade polycarbonate at specific thicknesses. Each thickness has to be tested independently. A test certificate for 10mm panels does not cover 6mm panels from the same product line.

Standard, non-FR polycarbonate generally lands at V-2 or HB, which means flaming drips. That is not a containment panel. It is a fire spread mechanism.

Multiwall polycarbonate is translucent, not clear. Light comes through, but you cannot read a label through it. For positions where visual equipment monitoring matters, clear PVC is the right choice.

Where multiwall polycarbonate is the correct call: HAC overhead ceilings and walls, CAC overhead enclosures, end-of-row panels where thermal separation is the goal, and blanking panels closing gaps above equipment racks.

Clear PVC Sheet: When the Technician Needs to See In

Multiwall polycarbonate is the right material for most containment positions. But there are places in a data center where you want to see what is happening without breaking containment: indicator lights, cable routing checks, equipment status, anything where opening an end-of-row door disrupts airflow management. That is where clear PVC earns its place.

PVC does not ignite easily. It stops burning when the ignition source is removed. Those are inherent material properties, not the result of FR additives. Clear PVC sheet also handles cleaning agents well, which matters in environments that get regularly wiped down.

It is also easier to cut and fit on-site than a framed multiwall system. For retrofit containment where custom-cut solid panels simplify installation, that matters.

What it does not do: insulate. A solid PVC sheet at equivalent thickness provides significantly less thermal separation than multiwall polycarbonate. If the primary design goal is reducing heat transfer between aisles, use multiwall. If the primary goal is visibility, use clear PVC. They are not interchangeable.

Clear PVC works well for end-of-row doors and visibility panels, side panels in cold aisle containment where safety requires a clear view into the aisle, retrofit applications where solid panels install more cleanly than framed multiwall systems, and cleanroom environments that require both visibility and regular chemical wipe-down.

GPO-3 Fiberglass: The Electrical Zone Material

Why GPO-3 Is Different From the Other Two

Polycarbonate and PVC are thermoplastics. Heat them enough and they soften. GPO-3 is a thermoset. The curing process creates permanent molecular bonds, so it holds its shape under thermal stress rather than deforming. That is the fundamental reason it is specified for electrical insulation rather than clear containment panels.

The bigger advantage in the electrical zone is arc resistance. When high-voltage electrical discharge contacts a thermoplastic surface, it can leave a conductive carbon trail (carbon tracking) that grows over time and eventually shorts the equipment. GPO-3 resists that tracking.

It also carries UL 94 V-0 and generates minimal smoke in a fire event. For switchgear housings, busbar supports, phase barriers, and transformer components, it is the material of record.

In the data center, GPO-3 belongs adjacent to power distribution units and busbar systems, inside switchgear panels as phase and end barriers, in UPS and battery rooms where arc resistance is a hard specification requirement, and anywhere a project spec or AHJ explicitly calls out arc and track resistance. It stays in the electrical rooms and power distribution zones. It is not a white-space containment material. It is opaque, orange-red, and not something you want between server rows.

How the Three Materials Compare

The table below maps each material against the spec attributes that drive containment decisions. Use it to confirm you are reaching for the right material, not just the one that was in stock.

The Specification Mistake That Keeps Happening

Polycarbonate is not one material from a fire rating standpoint. There are standard grades and there are flame-retardant grades, and they behave very differently under the UL 94 test. Standard polycarbonate typically achieves V-2 or HB. It passes the horizontal burn test. It burns slowly. But it produces flaming drips. Those drips land on the floor. They ignite adjacent equipment. V-2 is not a containment panel rating.

FR-grade polycarbonate uses flame-retardant additives to reach V-0. At 3mm or more in clear FR grades, and 1.5mm or more in opaque FR grades, V-0 is achievable. The rating is thickness-specific. A panel from an FR product line at 6mm does not automatically carry the V-0 certificate for 4mm panels from the same family. Each thickness has to be tested independently.

The scenario we see: a facilities team orders polycarbonate panels from a general supply house. The line item says "polycarbonate." Nobody specifies FR grade because the person writing the PO assumes polycarbonate is polycarbonate. The panels arrive, they look correct, they get installed. Months later a fire safety audit requests UL 94 documentation. There is none or the documentation covers a different thickness. The AHJ requires replacement. The whole installation comes out and goes back in with the right material.

Two lines on a purchase order prevent this. FR-grade polycarbonate. UL 94 V-0 certified at the installed thickness. Get the test certificate before the material ships. Farco carries FR-grade multiwall polycarbonate with the documentation to support it. That is part of why sourcing containment materials from a plastics distributor that knows data center applications matters more than sourcing from whoever has inventory.

Frequently Asked Questions

This article is for informational purposes only. Material selection, fire rating compliance, code requirements, and installation specifications must follow project documents, manufacturer datasheets, applicable building codes, and the authority having jurisdiction. Verify current standards, certifications, and material grades with the manufacturer and your design professional before specifying.