Finished Ventilation Duct Product

Layflat Positive-Pressure Ventilation Duct

Q: What diameter and section-length range is available?

A common configurable diameter range is 300 to 3000 mm. Section lengths may include 5, 10, 20, 30, 50, 100, 200 or 300 m, subject to design and production confirmation.

Q: What information is needed for a quotation?

Provide target airflow, fan data, total route length, bends, diameter, temperature, underground conditions, required standards, section length, coupling, suspension, quantity, destination and schedule.

A finished, collapsible air-forcing duct engineered to carry fresh air from a ventilation fan toward active work zones in tunnels, mines and underground construction projects.

DERFLEX supplies project-configured layflat duct sections with selectable diameter, length, coupling, suspension layout, color and performance treatment. The product is delivered as a fabricated ventilation duct—not as a roll of fabric—so buyers can specify the complete connection and installation format required for the jobsite.

Positive-pressure / blowing-air configuration

Request A Project Quote Review Key Attributes

Finished ProductFabricated sections ready for system installation

Long Air RunsConfigurable sections for underground project layouts

Low-Profile StorageCollapses flat when the blower is not operating

Project CustomizationDiameter, couplings, suspension and treatment options

Finished layflat positive-pressure ventilation duct section folded for transport

Complete Layflat Duct Section Collapsible body with fabricated end and suspension details—not unprocessed duct fabric.

Product Definition

What Is a Layflat Positive-Pressure Ventilation Duct?

A layflat positive-pressure ventilation duct is a flexible tube without a continuous internal wire helix. When connected to a suitable forcing fan, the fan inflates the duct and pushes fresh air along the tunnel or underground heading. When the airflow stops, the duct body can collapse substantially flat, which reduces transport and storage volume.

This configuration is normally selected where the ventilation objective is to deliver outside air toward workers, machines or the advancing face. It is distinct from a spiral-reinforced suction duct, which requires a structural helix to prevent collapse under negative pressure. Choosing the correct airflow mode is essential: a layflat positive-pressure duct should be matched to a blowing-air system rather than treated as a universal suction hose.

Why buyers choose the layflat format

Lower handling and storage volume than rigid or continuously wire-reinforced ducting
Fast extension as the excavation or underground work zone advances
Welded construction designed to limit unnecessary air loss along long runs
Multiple coupling and suspension choices for different project installation practices
Optional antistatic and flame-retardant configurations for specified environments

Engineered as a System Component

Performance Comes from the Whole Finished Duct

Reliable underground airflow depends on more than the coated textile. Seam construction, section geometry, couplings, suspension and installation discipline all influence leakage, friction, pressure stability and service life.

Air-Tight Welded Body

Heat-welded seams and carefully formed end details help reduce leakage points that can waste fan output before fresh air reaches the working zone.

Smooth Air Passage

A smooth inner surface and correctly tensioned installation help control turbulence and friction losses over extended duct routes.

Reinforced Suspension

Single or double suspension fins, patches, grommets or project-specific hardware can be selected according to diameter and installation load.

Configurable Connections

Zippers, hook-and-loop cuffs, steel rings, sleeves or eyelet systems allow the duct line to be extended, repositioned and repaired.

Underground-Ready Options

Flame-retardant, antistatic, cold-resistant or other treatments can be discussed where the operating environment and local rules require them.

Compact Logistics

Layflat sections can be folded for shipment and storage, supporting temporary works, remote sites and ventilation routes that move with the project.

Key Attributes & Specification Matrix

Buyer-Facing Technical Fields for Project Enquiry

The table covers the principal key-attribute fields commonly requested for tunnel and mine layflat duct procurement, including the diameter range, pressure class, fabric adhesion, antistatic value, connection and suspension details. Final values remain subject to the selected construction and confirmed test requirement.

Product name	Layflat Positive-Pressure Ventilation Duct	Finished flexible air-forcing duct; not a fabric roll.
Industry / application	Mining, tunneling, machinery and underground construction	Suitable for fresh-air supply in mine drifts, tunnel headings, metro works, hydropower galleries and similar projects.
Airflow mode	Positive pressure / blowing air	The duct inflates during fan operation; select a spiral-reinforced duct for suction or negative-pressure service.
Diameter / model range	300–3000 mm	Diameter should be calculated from required airflow, allowable air velocity, route length and fan performance.
Section length	5, 10, 20, 30, 50, 100, 200 or 300 m	Standard and custom section lengths can be discussed; handling and repair strategy should be considered for very long sections.
Body material	Reinforced PVC-coated polyester construction	Fabric grade and weight are selected according to pressure, diameter, abrasion exposure and project standard.
Wind-pressure resistance	Typical project range: 3000–10000 Pa	The required class must be confirmed against fan shut-off pressure, transients, diameter and safety margin.
Fabric adhesion strength	Typical selectable range: 60–100 N/50 mm	Actual value depends on the selected fabric grade and test method; include the required method in the enquiry.
Antistatic option	Surface resistance ≤3 × 10⁸ Ω, when specified	Antistatic performance is optional and must be stated in the purchase specification with the required test method.
Flame-retardant options	DIN 4102 B1 / EN 13501 / NFPA 701 / DIN 75200 options	Availability depends on the selected construction. Specify the exact standard, classification and documentation required before quotation.
Temperature guideline	Typical material range: approximately −30°C to +70°C	Confirm continuous temperature, cold-flex requirement and proximity to heat sources for the final product selection.
Color	Yellow, orange, black or custom	High-visibility colors are commonly used underground; custom color is subject to quantity and formulation.
Suspension	Single or double suspension fin / reinforced patch	A common reference is single suspension below 1800 mm diameter and double suspension at or above 1800 mm, subject to design.
Grommet spacing	Typical 750 mm	Spacing and hardware can be adjusted according to section weight, diameter, suspension cable and installation method.
Sealing sleeve	Typical 150–250 mm	End construction is coordinated with the selected coupling system.
Coupling choices	Zipper, hook-and-loop, steel ring or eyelet	Select for installation speed, leakage control, repair access and compatibility with existing duct sections.
Processing service	Cutting, heat welding and finished duct fabrication	Sections can be supplied with fabricated ends, suspension details and accessories according to approved drawings.
Brand / origin	DERFLEX / China	Company and product marking can be discussed for OEM or project identification requirements.
Packing	Folded sections, protective wrapping, pallet or project packing	Packing method is matched to section size, shipment mode and site handling plan.

How the Positive-Pressure System Works

From Fan Outlet to the Underground Work Face

A forcing system uses fan pressure to inflate the layflat line and move fresh air forward. Proper sizing and installation help retain useful pressure throughout the route.

Step 1

Fan Selection

Choose a fan that can provide the required volume after accounting for duct friction, leakage, bends and project length.

Step 2

Inlet Connection

Connect the first section securely to the fan transition so the airflow enters without an avoidable restriction or loose seal.

Step 3

Suspended Duct Run

Support the duct at consistent intervals, avoid sharp edges and maintain alignment to reduce deformation and pressure loss.

Step 4

Fresh Air Delivery

Position the outlet according to the ventilation plan and extend the line as the heading advances or the work zone changes.

Correct Product Selection

Layflat Positive Pressure vs. Spiral-Reinforced Ducting

The products can look similar in photographs, but they serve different pressure conditions.

Layflat Positive-Pressure Duct

Inflates when air is blown through the duct
Designed mainly for forcing fresh air toward the work zone
Collapses for compact storage and transport
Lower structural weight because no continuous helix is required
Common for advancing tunnel and mine ventilation runs

Spiral / Wire-Reinforced Duct

Maintains an open cross-section with a steel-wire helix
Can be configured for suction, exhaust or positive pressure
Better suited where the duct must resist collapse under vacuum
Usually bulkier in storage and shipment
Selected for dust extraction, exhaust and negative-pressure systems

Applications

Where Layflat Air-Forcing Ducts Are Commonly Specified

The same finished duct concept can be adapted to different project environments, but pressure, fire behavior, static control, diameter and installation details should be matched to each site.

Underground

Hard-Rock & Metal Mines

Fresh-air delivery to headings, equipment zones and temporary work areas in changing mine layouts.

Infrastructure

Road & Railway Tunnels

Ventilation support during excavation, lining, maintenance and other enclosed construction stages.

Urban Works

Metro & Subway Construction

Flexible air routes for stations, access shafts and advancing underground sections.

Energy

Hydropower Galleries

Temporary or project-stage fresh-air supply in tunnels, chambers and underground power works.

Excavation

TBM Support Ventilation

Long, extendable duct lines coordinated with tunnel boring operations and advancing faces.

Industrial

Confined Work Areas

Temporary positive-pressure ventilation where a portable, collapsible air route is more practical than rigid ductwork.

Product Images

Finished Duct Configuration, Installation and Packing

Images below are sourced from the DERFLEX website and show finished ventilation duct sections and underground installation references.

Layflat positive-pressure ventilation ducts installed in underground tunnels and mines — **Underground Installation Reference**Suspended layflat sections carrying fresh air through mine and tunnel routes.

Folded finished layflat ventilation duct product — **Collapsible Finished Section**Compact format for transport and storage.

Packed finished layflat ventilation duct sections — **Production & Packing**Finished sections prepared for project delivery.

Installation Priorities

Reduce Leakage, Friction and Premature Damage

Even a well-made duct can underperform when it is undersized, poorly supported or repeatedly dragged over sharp surfaces. The design review should therefore include both the product specification and the actual installation route.

Long runs require attention to fan pressure, couplings and leakage accumulation. A series of small leaks can substantially reduce the air volume delivered at the face. Bends should be gradual where possible, and the duct should be supported so it remains open and aligned under operating pressure.

Keep the duct clear of sharp rock, moving equipment and hot surfaces
Use the intended suspension points rather than piercing the duct body
Inspect couplings and welded areas during extension or relocation
Repair damage promptly with a compatible method and material
Re-check delivered airflow after major route changes or added sections

Maintenance & Inspection

Plan for a Moving Underground System

Ventilation routes often move as excavation advances. Section , lengths and coupling choice should make that movement manageable. Shorter sections can simplify isolated replacement, while longer sections can reduce the number of joints. The best choice depends on the site’s handling resources and leakage-control priorities.

Cleaning should use methods compatible with PVC-coated construction. Avoid aggressive solvents or uncontrolled heat. Before re-use, inspect suspension patches, end cuffs, zippers or rings, welded seams and any areas that have rubbed against supports. Ducts showing significant structural damage should be assessed before being returned to a high-pressure line.

For safety-critical environments, maintenance practice should follow the project ventilation plan, site risk assessment, local mine or tunnel rules and the documented product specification.

Procurement Guide

How to Specify the Right Layflat Ventilation Duct

A strong enquiry states the operating requirement rather than requesting only a diameter and color. This allows the duct construction and accessories to be matched to the full ventilation system.

1. Start with airflow and fan data

Provide the target m³/h or CFM, fan pressure curve, outlet size and operating point. Diameter selection based only on the fan outlet can be misleading over a long run.

2. Define the complete route

State total length, vertical sections, bends, junctions, expected extensions and the distance from the outlet to the working face.

3. Specify the operating environment

Include temperature, water exposure, abrasion risk, chemicals, dust, vehicle traffic and any special underground hazard classification.

4. Name the required standard

Do not write only “fireproof” or “antistatic.” Identify the required test standard, classification, report language and documentation format.

5. Choose section and coupling strategy

Balance joint count, leakage, installation speed, repair access and the manpower available to move or extend the line.

6. Confirm suspension details

Provide the suspension cable or support method, expected spacing and any hardware restrictions so reinforcement can be positioned correctly.

Why DERFLEX

A Practical Supply Route from Coated Material Knowledge to Finished Duct Fabrication

DERFLEX’s background in reinforced coated textiles supports communication between material selection and the needs of a fabricated duct. For buyers, the value is the ability to discuss the finished product in terms of fan pressure, duct size, joints, suspension, site conditions and documentation rather than treating every project as a standard fabric order.

Application-Based Configuration

Recommendations can be organized around airflow mode, route length, diameter, pressure class and underground operating conditions.

Finished Product Details

Couplings, end sleeves, suspension fins, grommet spacing, section length, color and packing can be included in the product discussion.

Project Documentation

Required test standards and documents can be identified before order confirmation, helping avoid vague or unsupported compliance language.

Related DERFLEX Resources

Explore the Ventilation Duct Product and Technical Cluster

These six internal links connect buyers with related finished-duct and technical information.

FAQ

Layflat Positive-Pressure Ventilation Duct Questions

Clear answers for contractors, mine operators, tunnel ventilation designers, equipment suppliers and distributors.

Is this page selling finished ventilation duct or only PVC-coated fabric?

This page is for a finished layflat positive-pressure ventilation duct. The product can include the fabricated duct body, welded seams, end connection, suspension reinforcement and packing specified for the project. Technical fabric information is relevant to performance, but the quoted item is not merely a roll of material.

Can a layflat positive-pressure duct be used for suction?

Normally no. A layflat duct depends on internal positive pressure to keep its cross-section open. Under suction it can collapse. Negative-pressure or exhaust applications generally require a spiral or wire-reinforced flexible duct designed to resist vacuum.

What diameter should I select?

Diameter should be calculated from required airflow, acceptable air velocity, total route length, friction, leakage, bends and available fan pressure. Provide the fan curve and target airflow so the product discussion is based on the system rather than diameter alone.

What diameter and section-length range is available?

A common configurable diameter range is 300–3000 mm. Section lengths may include 5, 10, 20, 30, 50, 100, 200 or 300 m, subject to design, handling requirements and final production confirmation.

Which coupling systems can be supplied?

Typical choices include zipper, hook-and-loop, steel ring, sleeve or eyelet-based connection formats. Selection should consider leakage, installation speed, compatibility with the fan and existing duct, repair access and the way sections will be extended underground.

Can the duct be flame-retardant and antistatic?

Optional flame-retardant and antistatic configurations can be discussed. Buyers should name the exact required standard and documentation rather than use general terms. Antistatic values such as surface resistance at or below 3 × 10⁸ Ω may be available for specified constructions, subject to test confirmation.

What pressure can the duct withstand?

Positive-pressure classes in the approximate 3000–10000 Pa range may be configured depending on diameter, fabric grade, seam design and section construction. The final class must be selected against the actual fan pressure and project safety margin.

How can leakage be reduced over a long tunnel run?

Use an appropriate pressure-rated construction, limit unnecessary joints, select secure couplings, support the duct correctly, avoid damage from sharp surfaces and repair punctures promptly. Airflow should be checked after each major extension because friction and leakage accumulate with route length.

What information is needed for a quotation?

Send target airflow, fan model and curve, fan outlet size, total route length, number of bends, required diameter if already calculated, temperature, underground conditions, fire or antistatic standard, preferred section length, coupling, suspension, quantity, destination and delivery schedule.

Can DERFLEX supply custom colors, markings or OEM packing?

Custom color, identification marking and project or OEM packing can be discussed according to order quantity, technical requirements and production confirmation. Include the artwork, marking position and packing expectation with the enquiry.

Specify the Duct Around Your Fan and Underground Route

Share the system data, required standard and installation method. DERFLEX can organize the quotation around the complete finished layflat positive-pressure ventilation duct rather than a generic fabric specification.

Useful documents to attach

Fan datasheet or pressure curve
Ventilation route drawing
Required test standard or tender specification
Connection and suspension photos or sketches

Request A Quote

Technical values on this page are typical reference ranges for project discussion and are not a universal guarantee for every configuration. Final performance, standard compliance, dimensions and documentation must be confirmed in the approved specification and order documents.