Most engineers, when they hear “ventilation duct,” picture galvanized steel or stainless — a metal box or round section hanging above a plant floor. That default is exactly why the question “what is a PP air duct?” is worth answering carefully: a PP air duct is not a metal duct with a plastic lining, and it is not a cheaper imitation of steel. It is a rigid duct extruded out of polypropylene, a thermoplastic whose chemical inertness — not its strength — is the reason it exists. This article is the definitional overview, written at a level a buyer or engineer can take straight into a project conversation: what the material is, what the duct is made of and how it is joined, the key physical properties with the numbers behind them, how it compares with metal, FRP and PVC, and the real sizes, wall thicknesses and temperature limits you design against.
Key Takeaways
- A PP air duct is a rigid ventilation duct extruded from polypropylene — the plastic wall itself is the corrosion barrier.
- Homogeneous construction — extruded PP sections joined by thermal fusion welding — no lining or coating that can delaminate or fail.
- Key numbers — density about 0.90–0.91 g/cm³, melting point around 160–170°C, continuous service typically to about 90°C, thermal expansion roughly 5–10× carbon steel.
- Corrosion boundary — resists most acids, alkalis and salts — but not strong oxidizers; media, concentration and temperature confirmed per project.
- Sizes — standard outer diameters φ20 to 600 mm, wall thickness stepped up by diameter (typical pairs — confirm).
- When to choose PP — corrosive and warm exhaust; reconsider for strong oxidizers, sustained over-temperature, heavy loads, or a fire classification the grade does not meet.
What a PP Air Duct Is
“PP” means polypropylene — a thermoplastic polymer
“PP” is the abbreviation for polypropylene, and it is the first thing the two letters stand for in a “PP duct.” Polypropylene is a thermoplastic polymer made by polymerizing propylene into long molecular chains, and it is one of the most widely produced plastics in the world (Wikipedia). Thermoplastic means the material softens when heated and hardens again when cooled, and that this can be done repeatedly. That single property is the reason the duct can be extruded from melted polymer into long sections and re-melted at the joints to weld them together.
The engineering behavior of the finished duct follows from two structural facts about the material. First, polypropylene is partially crystalline: in industrial products the degree of crystallinity typically runs 30–60%, so the wall is a mix of ordered crystalline regions (which give stiffness, hardness and resistance to solvents) and amorphous regions (which give toughness and flexibility). Second, PP is non-polar, which is the molecular reason for its chemical inertness — a point that returns in the properties section below. Together these facts explain why PP duct behaves the way it does across density, temperature and chemical resistance, and why the honest answer to most “what is” questions about it is a range plus “depends on grade.”
What a PP air duct is (and is not)
A PP air duct is a rigid, homogeneous plastic duct extruded from polypropylene, used in ventilation and exhaust systems that move corrosive air, vapors or fumes. It is a category of ductwork: a pressure-ventilation component that carries air at near-atmospheric pressure, as opposed to a pipe, which carries pressurized fluids — the one-sentence distinction between a “pp duct” and a “pp pipe,” which is sized and rated on completely different rules. A PP duct is specified by its cross-section, wall thickness and the airflow it must move; a PP pipe is specified by a pressure rating.
It is also important to say what it is not. It is not a metal duct with a plastic coating or lining — the entire wall is polypropylene. It is not a flexible or foil duct, which is a different, consumer-oriented product family. And it is not a composite in the fiberglass sense: there is no reinforcing layer and no coating to wear off. When people say “plastic air duct” in an industrial context, this homogeneous extruded PP duct is usually what they mean — and knowing exactly what it is not is as useful as knowing what it is, because each of those exclusions removes a failure mode the alternatives have.
Polypropylene grades: PP-H, PP-B, PP-R and duct service
Polypropylene is not one material but a family. The three grades most often encountered are PP-H (homopolymer), PP-B (block copolymer) and PP-R (random copolymer), which differ in impact behavior, temperature response and chemical profile. Duct service commonly uses PP-H — an enhanced homopolymer grade and a standard choice for fume and chemical exhaust ducting, commonly quoted for continuous service up to about 90°C (Quimipol) — but the important habit to build is always asking which grade a product is.
The reason grade matters is that physical properties are grade-dependent. Whether the polymer is homopolymer or copolymer, and its degree of isotacticity, directly change crystallinity, and through it the melting point, stiffness, hardness, impact strength and creep resistance of the finished part (Wikipedia). Isotactic PP crystallizes more readily and therefore has the higher melting point — the commonly quoted 160–170°C sits at the top of the general polypropylene melting range. This is why a responsible definitional answer gives ranges and the phrase “depends on grade,” and why a project order should state the grade (PP-H, PP-B or PP-R) before it relies on a temperature or chemical-resistance number.
Where PP duct sits in the plastic duct family
Polypropylene is one of several plastics used for industrial ductwork, and the position of PP in that family explains most selection decisions. In rough terms: PVC is economical but its continuous service limit is lower (typically about 60°C); CPVC extends higher, commonly quoted around 93°C; PP sits above standard PVC at about 90°C typical, lighter than PVC and with broad chemical resistance; PVDF is used where the chemistry or temperature exceeds what PP can take, at significantly higher cost; and FRP is the reinforced composite family, stronger and heavier, with behavior set by its resin matrix. For the bulk of corrosive, warm fume exhaust, PP is the material the family table keeps returning to.
Knowing the family position also corrects a common mis-framing. The real choice in a corrosive exhaust project is rarely “plastic duct vs metal duct” as an abstraction — it is “which plastic, in this medium, at this temperature, under this load.” That is the frame the comparison section below builds, and it is the same frame the dedicated material-selection guide (duct materials for corrosive fumes) treats in depth for specific chemicals.
What Is PP Duct Made Of?
Extruded, homogeneous PP duct sections
PP duct starts as polymer pellets that are melted and forced through a die to form a continuous pipe, which is then cut to length. Extrusion produces a homogeneous wall: the material is the same all the way through, with no layer structure. That homogeneity is the basis of the duct’s corrosion performance — there is no thin surface film whose failure would expose an unprotected substrate, and no boundary layer where two materials could separate under thermal cycling.
The practical consequence is that a scratch or minor abrasion does not create a corrosion path the way it does on coated metal. The duct’s protective wall is the full thickness of the plastic, not a coating, so damage that would destroy a lined system merely thins the same material by a fraction of a millimeter. (Fabrication and welding details are a subject of their own; this article keeps to the definition, and the manufacturing process is covered as a separate topic that will be linked here when published.)
Thermal fusion welding joins the run
Individual sections are joined into a continuous run by thermal fusion welding — typically butt welding or socket welding. The mating surfaces are heated until the PP softens, pressed together, and fuse into one continuous material as they cool. Because both parts are the same polypropylene, the weld is part of the same homogeneous plastic rather than a seam between two different materials, and a properly made weld is effectively a continuation of the duct wall.
Fusion welding matters for corrosion service in a specific way: it leaves no gasket, no mechanical fastener and no crevice where liquid can pool and attack. Metal duct runs are assembled with fasteners, gaskets and sealants, each of which is a potential failure point in a corrosive airstream. A welded homogeneous PP run removes that entire class of joints — which is why long corrosive-exhaust runs can be assembled without the joints becoming the weak points of the system.
The material itself is the corrosion barrier — no lining, no coating
Put the two previous points together and the design principle emerges: in a PP duct, the corrosion barrier is the duct. There is no internal lining to blister, no coating to chip, and no exposed substrate where the coating is scratched. The plastic wall — full thickness — is what the medium contacts.
| Construction | What the medium contacts | Where failure starts |
|---|---|---|
| Homogeneous PP duct | the full plastic wall, the same material throughout | nowhere by design — a scratch exposes the same material, not an unprotected substrate |
| Lined or coated metal duct | a thin lining or coating over a metal substrate | a scratch, chip or delamination exposes the metal underneath, which then corrodes |
That is the structural reason PP duct exists as a category. Where the medium is corrosive and the operating temperature is moderate, a homogeneous plastic wall can outlast a metal wall that corrodes, even though the metal is stronger. Strength is the wrong axis to compare on for this service; chemical inertness over the design life is the axis that decides.
Thermal expansion: a property every long run must handle
One consequence of the material being a polymer is often underestimated by engineers who come from steel: polypropylene expands with temperature far more than metal does. The linear coefficient of thermal expansion of extruded PP is typically in the region of 0.10 to 0.15 mm per metre per degree Celsius (material-handbook values for extruded PP), against about 0.012 mm per metre per degree Celsius for carbon steel — an order-of-magnitude difference. Wikipedia describes the thermal expansion of PP as significant, and it is significant in real numbers: a 30-metre straight run of PP duct that warms by 30°C grows by roughly 0.11 m — about 110 mm, or about 4.3 inches of length change on a run of about 98 ft — that the ductwork must be able to absorb without binding or overstressing the joints.
That is why long PP duct runs are not installed as rigid, fixed assemblies the way short steel runs can be. Expansion is handled with expansion joints or bellows at intervals, and with a support scheme where some hangers fix the duct while others allow axial movement — the classic fixed-point and guide-hanger arrangement used for plastic piping systems. The thermal-expansion figure belongs on the datasheet of any serious supplier, and a sizing and layout question it raises is part of the design work covered in the ventilation duct sizing guide.
Key Properties at a Glance
Lightweight: density around 0.90–0.91 g/cm³
Polypropylene has a density of about 0.90–0.91 g/cm³, which is 900 to 910 kg/m³ — lighter than water (about 1,000 kg/m³) and roughly one-eighth the density of steel (about 7,800 kg/m³). A PP section of the same volume is therefore roughly 85% to 90% lighter than a steel section. For ductwork this shows up as much lower weight per meter of run, which changes the support and hanging design compared with metal duct, and reduces the structural load on the building. The table below compares the common duct materials; the PVC density follows its Wikipedia data.
| Material | Typical density (g/cm³) | Engineering note |
|---|---|---|
| Polypropylene (PP) | 0.90–0.91 | about 900–910 kg/m³; lighter than water; roughly 1/8 the density of steel |
| Polyvinyl chloride (PVC) | about 1.4 | about 1,400 kg/m³; heavier than PP — same-volume wall weighs ~55% more |
| Carbon steel | about 7.85 | about 7,850 kg/m³; the common metal baseline for HVAC duct |
| Water | about 1.0 | about 1,000 kg/m³; reference point |
The lighter weight also changes how the duct is handled and installed. Hanger spacing and support details for plastic duct differ from steel practice, and the flimsier feel of a plastic section compared with steel is normal — it is not a sign of a defect. The trade-off is accepted because the application has already been chosen for corrosion performance rather than for raw strength.
Stiffness in context: strength is not the point
The mechanical numbers deserve their own honest treatment, because “is plastic as strong as steel” is the first question every metal-oriented engineer asks. Polypropylene’s Young’s modulus — the stiffness of the material — is on the order of 1.3–1.8 GPa for common grades (Wikipedia), against roughly 200 GPa for carbon steel. That is a factor of more than 100 in material stiffness. What that means is not that PP duct is too weak to work; it means PP duct must be designed differently: spans are kept shorter, wall thickness carries the stiffness, and supports are placed closer together.
This is the physical reason wall thickness is stepped up with diameter (the sizing table in the last section), and the reason plastic duct hangs with a different support scheme than steel. When someone handles a PP section and it deflects more easily than a steel one, that is expected material behavior, not a defect. The design discipline is to treat the duct as a low-stiffness structural element and support it accordingly — a consequence of choosing the material for corrosion performance, not for load-bearing strength.
Temperature: melting point vs continuous service (about 90°C)
Two different temperature numbers are often confused. The melting point of polypropylene is in the range of about 160–170°C for the high-crystallinity (isotactic) grades used in ductwork — toward the top of the general polypropylene melting range of roughly 130–171°C. But that is not a working temperature: it is where the polymer stops being a solid. The continuous service temperature is far lower — for PP-H duct grades, commonly quoted values sit up to about 90°C, and the actual limit depends on grade and mechanical load.
There is a third number that matters for low temperatures: the glass-transition temperature of PP sits around −10°C (material-handbook values vary with grade and crystallinity). Below it the amorphous regions become glassy and the material turns brittle; above it, PP is in its tough, rubbery state. For the typical operating window of fume exhaust ducting — roughly 0 to 60°C — PP is comfortably above its glass transition, which is why cold brittleness is rarely the controlling failure mode for PP the way it can be for PVC. Designing to the melting point is the classic error. A duct that softens at elevated temperature will sag and lose its pressure rating long before it melts, and the ceiling for continuous use is the service temperature, not the melting point — and that service ceiling is itself load-dependent, as the next point explains.
Creep: why continuous temperature depends on load
Every plastic creeps: under a sustained load it slowly deforms over time as polymer chains rearrange, and the rate increases sharply with temperature. The crystallinity of PP acts as a built-in brake on this — the crystalline regions resist chain slippage, which is why a higher-crystallinity grade is more creep-resistant than a purely amorphous one — but the general rule stands: the hotter the duct, the faster a given load deforms it.
This is the mechanism behind the phrase “depends on grade and load” that appears on every PP temperature rating. An unpressurized horizontal duct carrying only its own weight can run hotter than the same duct under heavy mechanical loading, sustained internal pressure, or a long unsupported span. So the continuous-service figure of about 90°C is not a hard wall — it is the typical ceiling for common configurations, and the correct project question is “what temperature, under what load, for what service life.” That single habit of asking the three together prevents the most common PP duct failures: sagging between supports and long-term deformation at elevated temperature.
Chemical resistance — and where it stops
Polypropylene’s reason for existing in ductwork is broad chemical resistance, and the mechanism is worth stating once. PP is non-polar and its crystalline regions are tightly packed, so polar, water-based media — most acids, alkalis and salt solutions — find little to attack in the polymer structure. That is why PP is a standard choice for laboratory and chemical exhaust. The engineering boundary, though, is real, and it follows from the same mechanism:
| Medium | Typical PP behavior |
|---|---|
| Acids, alkalis and salts (aqueous) | Generally resistant |
| Strong oxidizers (e.g., fuming sulfuric acid, high-concentration oxidizing acids) | Not suitable — confirm |
| Many organic solvents | Partial, media-dependent — confirm |
Strong oxidizers are the exception because oxidizing attack can break the polymer’s carbon backbone itself — damage that no amount of wall thickness postpones indefinitely. Resistance is not a single on-off property. Concentration and temperature act together: a chemical that is harmless diluted and cool (near 20°C) can be aggressive concentrated and warm (at 60°C). The safe discipline is to confirm the actual medium, concentration and temperature against the grade’s data before ordering — a habit this article can state but only the project can execute. Per-chemical compatibility in detail is the job of the material-selection guide linked earlier.
Flammability: standard PP vs flame-retardant PP
Plastics are classified for flammability under UL 94, a standard that grades materials from HB through V-2, V-1 and V-0, where V-0 is the highest common rating and is based on vertical-burn behavior with self-extinguishing within seconds. Standard (unmodified) polypropylene is combustible — it is a hydrocarbon polymer, and when heated it decomposes into flammable volatiles that sustain burning.
Flame-retardant (FR) PP is modified with additives that interrupt that decomposition and change the burn behavior, moving the grade up the UL 94 scale. So “is PP duct fire retardant?” has no single answer — it depends on whether the specific grade is standard or FR, and on the classification the project requires. For a project with a fire-performance requirement, the deciding step is to name the classification the duct must meet — HB, V-2, V-1 or V-0 — and select a grade that is documented to meet it. The standards and rating details are their own topic; the definitional takeaway here is that “PP duct” and “flame-retardant PP duct” are not the same product, and the classification detail is covered as a separate topic that will be linked here when published.
PP Duct vs Metal, FRP & PVC
PP duct vs galvanized steel and metal duct
Galvanized steel is the default duct material for general HVAC: strong, economical and well understood. Its weakness is corrosion, and the mechanism matters. The zinc coating protects the steel sacrificially, but where the coating is cut, scratched or worn — at flanges, fasteners, seams and bends — the exposed steel corrodes, and in an acid or salt-laden airstream that corrosion runs inward from the internal surface, often invisibly until the wall thins or leaks. The metal’s strength advantage is progressively eaten away until the duct fails.
That is the crux of the whole comparison. In clean-air ventilation, steel’s strength and cost usually win. In corrosive service, the strength is irrelevant if the wall corrodes, and the chemically inert PP wall becomes the deciding factor — which is why “plastic duct vs metal duct” is answered by the medium first, not by strength. It is also worth noting that “metal” is not automatically safe: stainless steel, for example, pitting and stress-corrosion-cracking in chloride service, so the metal-versus-plastic question should be asked per medium, not per material class. Add the weight difference, and PP also imposes less load on supports.
PP duct vs FRP (fiberglass-reinforced plastic)
FRP (fiberglass-reinforced plastic) is the other major corrosion-resistant duct family: it offers strong chemical resistance with higher mechanical strength, and is used in demanding corrosive and chemical service. The two materials overlap in application but differ in character. FRP is a reinforced composite — a resin matrix carrying glass-fiber reinforcement — fabricated by processes like filament winding or hand layup rather than by extrusion, and it is typically heavier and stiffer than PP.
The critical habit with FRP is to remember that its corrosion and temperature limits are set by the resin matrix, not by “fiberglass” in the abstract — vinyl ester and phenolic systems extend temperature and chemical capability, and the supplier’s chemical-resistance data sheet is the arbiter. The choice between FRP and PP is usually project-specific rather than absolute. FRP can carry higher loads and large spans; PP is extruded, lighter, and joined on-site by welding into a homogeneous run. Cost, fabrication, and structural requirements decide, and a one-sentence summary can only say: both are corrosion-resistant, FRP brings more strength and weight, PP brings lightness and homogeneous welded construction — pick by structure and media.
PP duct vs PVC duct
PVC is a common, economical plastic duct in laboratory and fume service, and it overlaps PP in application. The key distinction is temperature. Standard PVC has a typical continuous service limit of about 60°C — a figure that is simultaneously a structural limit and a corrosion-performance limit, since both fall off together above it — while CPVC extends higher, commonly quoted around 93°C, and PP commonly sits above standard PVC with typical continuous service around 90°C. On density, PVC at about 1.4 g/cm³ (about 1,400 kg/m³) is heavier than PP at 0.90–0.91 g/cm³ (about 910 kg/m³), so a same-volume PVC wall weighs roughly 55% more.
For a warm corrosive exhaust — a fume stream that is both acidic and above ambient — the temperature ceiling is often what separates them. If the exhaust runs cool, PVC’s lower cost may win; if it runs warm, the extra headroom of PP is the deciding factor. As with all these comparisons, media compatibility for the specific chemical still has to be checked, and per-chemical detail is covered in the selection guide.
When a PP duct is NOT the right choice
The boundaries are as important as the strengths. A PP duct is the wrong choice when the medium includes strong oxidizers such as fuming sulfuric acid or high-concentration oxidizing acids, because oxidizing attack degrades the polymer backbone itself. It is the wrong choice when sustained service temperature exceeds what the grade can take — and remember that the practical ceiling is the load-dependent service temperature, not the melting point. It is the wrong choice when the duct must carry heavy mechanical loads where a reinforced or metal structure is needed, or where very long unsupported spans are unavoidable. And it is the wrong choice when the project’s fire-performance requirement specifies a classification that the chosen grade does not meet.
For example, a warm dilute-acid exhaust at 60°C sits comfortably inside the typical PP envelope, while the same medium concentrated and hot — sustained service above about 90°C, or a strong oxidizer — moves the choice to a confirmed grade or a different material (FRP or PVDF are the usual directions). When the medium or temperature is uncertain, the correct move is to confirm with the manufacturer and, for genuinely borderline cases, to test. The definitional rule here is simple: know the medium, know the temperature, and if either is uncertain, do not assume. The application context for where PP is used in practice is in the PP duct applications overview.
A three-input selection frame: media, temperature, load
The comparison section above can be condensed into a working frame that any engineer can apply without a chemistry degree. Every selection decision for corrosive exhaust ductwork is set by three inputs: the media (what is in the airstream, at what concentration), the temperature (continuous peak, not occasional), and the load (span, self-weight, pressure class, mechanical duty).
| Input | What to establish | Why it decides |
|---|---|---|
| Media | Chemical identity + concentration of each component | Sets chemical-resistance boundary — strong oxidizers rule out standard PP |
| Temperature | Continuous operating peak, with margin | Sets grade ceiling — compare against the ~90°C typical service limit |
| Load | Span, self-weight, pressure class, mechanical duty | Sets wall-thickness and support needs — and derates the temperature ceiling via creep |
Run the three inputs against the tables in this article — the chemical boundary, the temperature rating, the density and stiffness numbers, the diameter and wall-thickness table — and “is PP duct the right choice” answers itself for the common cases. What the frame cannot do is replace the supplier’s data for a specific configuration or a genuinely borderline chemical; that is where confirmation and testing take over. This three-input logic is the same method the dedicated selection guide applies chemical-by-chemical, and it is the definitional article’s real payoff: not a verdict for every project, but a decision structure that works for every project.
What Is PP Duct: Sizes, Wall Thickness & Temperature Rating?
Standard outer diameters: φ20–600 mm
PP duct is manufactured in standard outside diameters, and the typical factory range runs from 20 mm up to 600 mm outside diameter (φ20 to φ600 mm). The range covers both small laboratory branches and large main exhaust headers, so most projects can land on a stock size rather than a custom extrusion. The size series exists precisely so that a calculated airflow diameter can be rounded up to the next stock size instead of being extruded specially.
The range is a reference, not a commitment: exact availability and made-to-order sizes should be confirmed for each project. When a sizing calculation is part of the job — computing the diameter a given airflow and velocity require — the ventilation duct sizing guide shows how a calculated diameter is rounded up to the next stock size; the same discipline applies to PP as to any duct material.
Wall thickness by diameter — and why it steps up
Wall thickness is stepped up with diameter for a mechanical reason: a larger duct must carry more stiffness across a longer unsupported span, and because the material is a low-modulus plastic (see the stiffness discussion above), that stiffness comes from wall thickness rather than from material strength. A representative set of typical pairs is:
| Outside diameter | Typical wall thickness |
|---|---|
| φ110 mm | 3 mm |
| φ160 mm | 4 mm |
| φ250 mm | 4 mm |
| φ400 mm | 5 mm |
| φ600 mm | 6 mm |
Read the table the right way: these are typical pairs — the wall thickness that commonly accompanies each diameter, not a full-series guarantee. In plain terms, the typical wall thickness spans 3 mm to 6 mm across diameters from 110 mm to 600 mm. Wall thickness interacts with pressure class, span, self-weight and the grade used, so the confirming question to a supplier is “what wall thickness comes with this diameter in this grade,” rather than assuming any single value. The purchasing overview on how to buy PP duct covers the questions to ask.
Temperature rating by grade — and why project confirmation matters
The temperature table that governs the whole definition:
| Condition | Typical continuous service |
|---|---|
| PP-H, common duct grades | up to about 90°C, grade- and load-dependent |
| Sustained service near or above the limit, or aggressive media | confirm with manufacturer; consider testing |
“What is a PP duct used for” follows from this table: corrosive and warm exhaust — laboratory fume exhaust, chemical process ventilation, plating and pickling lines, food-industry exhaust where washdown chemicals are present. Where the medium is corrosive and the temperature fits the grade, PP duct is a candidate; where either condition is pushed beyond typical bounds, the answer moves to another material or a tested grade.
The phrase “confirm for the project” is doing real work here. Temperature ratings depend on grade, wall thickness, load and the specific medium, and no definitional article can replace the manufacturer’s data for a particular configuration. The load dependency is not a caveat — it is the creep mechanism described earlier, and it is why the correct question pairs temperature with loading. And note what these numbers are not: PP melts around 160°C to 170°C, but the table above is about the much lower ceiling for continuous use — a service rating, not a melting point. What this article can do is give you the correct numbers to quote and the correct questions to ask.
How to use these numbers: a working checklist
The definition in this article becomes a decision aid when the numbers are assembled into a sequence. A working checklist for a corrosive exhaust project:
1. Name the medium — each component chemical and its concentration; check it against the chemical boundary table (strong oxidizers rule out standard PP).
2. Establish the temperature — the continuous operating peak, with margin; compare it against the ~90°C typical service limit and ask what load applies at that temperature.
3. Pick the size — the calculated airflow diameter, rounded up to a stock size in the φ20–600 mm range.
4. Confirm wall thickness — the typical pair for that diameter, then confirm the actual thickness in the specified grade.
5. State the grade — PP-H, PP-B or PP-R, because physical properties are grade-dependent.
6. Confirm with the supplier — the typical pairs, the temperature-with-load rating, and the media compatibility for that specific configuration.
That sequence is the practical answer to “what is a PP air duct” in engineering terms: a material, a construction, a set of properties, and a confirmed specification. What it deliberately does not do is pretend that a definitional article can replace the manufacturer’s data for a specific medium at a specific temperature — the checklist ends where confirmation begins.
What to do next
The next practical step is to take the definition and the numbers to the PP air duct product page for the full size range and specification, or browse the general product range for other duct materials. From there, the rest of the guide cluster builds the picture: this definition sits inside the overall PP air duct guide, the material-selection and corrosion comparison lives in the duct materials for corrosive fumes guide, and the sizing and purchasing guides cover the calculation and procurement side.
Three related topics are planned for this cluster and will be linked from this article when published: the manufacturing and welding process in detail, a dedicated overview of the advantages of PP duct for exhaust service, and the flame-retardant grades and classifications. Until those pages go live, the definitional treatment above is the complete story this page intends to tell — a clean, informational answer to “what is a PP air duct” that a buyer or engineer can take straight into a project conversation. With the size, wall thickness, temperature and grade numbers from this page in hand, you can decide whether a PP duct fits your project — and the next links let you confirm the remaining details.
