Flexible underground airflow systems
Project-configured tunnel ventilation duct for fresh-air supply, local exhaust and changing underground routes—specified as a working air path rather than a generic fabric tube.
DERFLEX supplies flexible tunnel ventilation ducting with selectable duct structure, diameter, section length, suspension, couplings and project-defined performance options. The configuration can be reviewed against fan data, route length, pressure direction, bends, clearances and the installation sequence before production.
During excavation, the work face moves while duct length, hanging points and local restrictions change. A useful product specification therefore begins with the planned air route and operating mode.
A fan pushes fresh air through the tunnel ventilation duct toward the active heading. Collapsible layflat construction is commonly evaluated because internal pressure keeps the air passage open during operation and the duct can be packed compactly between moves.
View positive-pressure ducting →Where contaminated air, dust, fumes or heat must be drawn through the duct, the air passage needs structural support. Rings or a continuous wire helix help the duct resist collapse under negative pressure and through bends.
Review spiral-reinforced duct →In narrow drifts, utility tunnels or equipment-dense headings, a full round section may interfere with vehicles, services or the crown. Oval or twin-chamber layouts can be considered where preserving vertical clearance is part of the installation plan.
Fan model, operating airflow and pressure are more useful than fan power alone. They help determine whether the planned duct diameter and line length are practical.
Diameter affects air velocity, friction and space occupation. Route length adds cumulative resistance and makes leakage control at each section connection more important.
Welded body seams, coupling overlap and connection count influence how much fan output reaches the working zone. A smooth internal air path also helps limit unnecessary flow resistance.
Elbows, reducers, Y-pieces and fan interfaces should be included in the route review. Repeated tight bends can require a shape-retaining duct section rather than a fully layflat tube.
Hanging fins, eyelets, reinforced patches and section weight influence installation speed and local stress. The suspension layout should suit tunnel crown conditions and planned duct relocation.
Flame-retardant or antistatic performance should be specified with the required standard, test method and acceptance value. Category labels alone do not define final compliance.
The finished duct is a coordinated assembly of coated textile, welded seams, reinforcement, suspension and end connections. Performance depends on how these parts work together.
DERFLEX uses PVC-coated polyester technical textile as a common construction platform for flexible tunnel air duct assemblies. Material weight, yarn structure and coating formulation can be matched to pressure, handling, abrasion and safety requirements.
Buyers that fabricate locally can also review the dedicated PVC fabric for tunnel ventilation duct page. Finished-duct buyers can specify welded sections with suspension details and selected end interfaces.
Use this table as an RFQ framework. Final values depend on the completed duct construction, fan duty, route layout and the approved project datasheet.
| Specification Item | Typical Project Options | Why It Matters |
|---|---|---|
| Product form | Layflat duct, ring-supported duct, spiral-wire duct, low-profile duct or custom transition | Selected mainly by positive/negative pressure, bends, handling and tunnel clearance. |
| Duct body | PVC-coated polyester technical textile | Fabric structure and coating are matched to air containment, welding, wear and project treatments. |
| Reference fabric weight | Approx. 400–900 g/m2 or project-specific | Weight alone does not define duct pressure capability; yarn, seam, reinforcement and diameter also matter. |
| Diameter | Approx. 300–3000 mm; custom review available | Chosen from airflow requirement, pressure loss, fan curve and available headroom. |
| Section length | Project-defined; common fabricated sections may be 1–100 m, with longer options reviewed by design | Longer sections reduce joint count but increase handling weight and installation difficulty. |
| Connections | Zipper, steel ring, clamp, drawstring cuff, hook-and-loop or drawing-based interface | Connection choice affects extension speed, compatibility, sealing and field replacement. |
| Suspension | Reinforced fin, eyelets, D-rings, patches or custom hanger layout | Correct load distribution helps reduce concentrated stress during inflation, movement and relocation. |
| Reinforcement | None, periodic rings, continuous spring-steel helix, wear strip or custom reinforcement | Shape support is usually required when suction, tight bends or repeated contact can collapse or damage the duct. |
| Performance options | Flame-retardant, antistatic, cold-resistant, abrasion-oriented or high-visibility formulations | Any safety or performance claim should be linked to the named project test method and acceptance criteria. |
Reference values are intended for quotation planning and product comparison, not as a universal performance guarantee. Confirm the final construction, tolerances and test requirements on the approved technical document before ordering.
The practical choice depends on whether the fan pushes or pulls air, how the line must bend, and how much space is available above the tunnel traffic envelope.
Commonly selected for forced fresh-air delivery to advancing headings.
Shape-retaining flexible construction for suction, extraction and difficult routing.
Alternative profile where a round tunnel air duct conflicts with equipment or services.
Flexible ducting is particularly useful where the air route must extend, relocate or pass through confined construction space while the project progresses.
Temporary fresh-air delivery and extraction during drilling, blasting, lining, equipment operation and staged underground work.
Extendable ventilation lines for long underground alignments where the face and work zones continue to move.
Flexible routing for station boxes, cross passages, shafts and tunnel headings where clearance is shared with equipment and services.
Project-configured air supply or extraction for access tunnels, diversion tunnels, underground chambers and maintenance zones.
Temporary ventilation in cable, pipeline and civil utility corridors where rigid duct installation may be impractical during construction.
Custom duct diameter, cuffs, connectors, labeling and packaging can be coordinated around blower or auxiliary fan packages.
A complete brief helps the quotation reflect airflow duty, installation effort and project documentation—not just a price per meter.
Underground projects may require specific fire behavior or surface-resistance limits. These should be stated in the RFQ so material formulation, finished-duct construction and documentation can be reviewed against the same requirement.
Requirements differ by market, project owner and application. DERFLEX can discuss optional flame-retardant and antistatic configurations, but the requested standard, test method and acceptance value should be confirmed before production.
For underground projects with a documented safety specification, review the antistatic flame-retardant ventilation duct configuration and provide the applicable project requirement with the RFQ.
DERFLEX can support buyers that need complete fabricated duct sections as well as customers that purchase coated ventilation fabric for local conversion.
Welded body, cuffs, suspension details, selected couplings and optional reinforcement can be quoted as one fabricated product.
PVC-coated textile construction can be reviewed against pressure direction, abrasion, handling and project-specific treatment requirements.
Reducers, bends, branch pieces, fan connections and drawing-based end interfaces can be discussed for route compatibility.
Sections can be labeled by diameter, length, route or installation sequence to support site handling and staged installation.
These DERFLEX pages cover adjacent duct formats, fabrication options and material selection without repeating the same purchasing question.
Practical answers for contractors, ventilation equipment suppliers, tunnel project buyers and distributors preparing a duct specification.
A tunnel ventilation duct creates a controlled air path between a fan and an underground work zone. Depending on the system, it can carry fresh air toward an advancing heading or extract contaminated air, dust, fumes and heat from a localized area.
The terms are commonly used for the same product category. “Tunnel ventilation duct” often refers to one duct section or product, while “tunnel ventilation ducting” may describe the full run, multiple connected sections or the overall flexible air-distribution system.
Layflat construction is commonly evaluated for positive-pressure fresh-air supply because fan pressure inflates the tube. Spiral or ring-reinforced construction is normally considered when the duct must remain open under suction, negotiate repeated bends or maintain shape at equipment connections.
Diameter should be reviewed against the required airflow, target air velocity, fan curve, static pressure, total route length, bends, leakage allowance and available tunnel clearance. Selecting only from fan power can miss important pressure-loss and installation factors.
Yes. DERFLEX can review project-specific diameter, fabricated section length, suspension, end cuffs, zipper/ring/clamp interfaces, reinforcement, branches, reducers and other connection details. Final availability depends on the confirmed duct structure and order specification.
Project-specific flame-retardant and antistatic configurations can be discussed. The required standard, test method, acceptance value and documentation should be included in the RFQ so the proposed construction can be reviewed against the actual project requirement.
Share airflow mode, fan data, total line length, tunnel clearance, preferred section length, coupling method and any named safety test. DERFLEX can review a tunnel ventilation duct configuration around the actual installation conditions.