1
Match the fan
Confirm the physical outlet interface instead of relying only on the nominal fan size.
Flexible airflow systems · project & OEM supply
Confined Space Ventilation Duct
Flexible ducting configured for portable blowers and extractors used around tanks, manholes, utility vaults, process vessels, ship compartments and controlled-entry maintenance work. DERFLEX can develop the duct around the actual fan outlet, airflow direction, route, connection and specified safety-related requirements.
- Portable blower matched
- Supply or extraction
- Layflat or wire reinforced
- Custom cuffs & lengths
- FR / antistatic options by requirement
Specify the air route, not just a hose size
A confined space duct should be selected around the ventilation system
A useful confined space ventilation duct does more than connect to a fan. It must remain compatible with the pressure direction, fit through restricted openings, tolerate repeated deployment, route air toward the occupied zone and connect securely to the equipment used on site.
That is why DERFLEX starts with the fan and the entry layout. For positive-pressure fresh-air delivery, a compact collapsible design may reduce storage volume and handling weight. For suction or exhaust duty, the duct normally needs shape-supporting reinforcement so negative pressure does not pull the airway closed. Routes with several bends, vertical drops or frequent relocation can change the reinforcement and cuff decision again.
This purchasing logic is particularly relevant for safety-equipment distributors, industrial maintenance contractors, shipyards, utility crews, rental fleets, fan manufacturers and OEM programs that need repeatable duct assemblies rather than generic fabric tubing.
2
Choose pressure mode
Positive pressure and negative pressure place different structural demands on flexible ducting.
3
Map the route
Length, bends, access opening and delivery point influence practical duct architecture.
4
Confirm requirements
Define the material, connection, marking and any test method before production approval.
Airflow architecture
Fresh-air supply, extraction or a reversible portable setup?
The airflow direction is one of the most important distinctions in confined space blower ducting because it affects whether the hose can rely on internal pressure to stay open.
Fresh-Air Delivery
The blower pushes clean air through the hose toward the target work zone. A collapsible or lightly supported duct may be considered when compact storage and repeated movement are important.
- Portable axial blower connections
- Manholes, tanks and utility chambers
- Compact transport and storage
Exhaust & Extraction
When a fan pulls air through the hose, negative pressure can collapse an unsupported body. A spiral wire-reinforced or otherwise shape-retaining structure is normally evaluated for this operating mode.
- Local exhaust routes
- Fume, heat or odor removal systems
- Bends, drops and compact routing
Reversible / Multi-Use
Rental fleets and maintenance teams may want one duct format usable on either side of a compatible fan. A reinforced construction is normally reviewed, together with connector orientation and handling requirements.
- Shared maintenance inventory
- Portable ventilation kits
- OEM blower packages
Material & finished construction
PVC-coated technical textile, fabricated into a blower-ready duct assembly
DERFLEX's broader flexible ventilation range uses woven or knitted polyester technical textile with PVC coating on both sides, with formulation and textile structure selected by the application. For confined-space work, the coated body must be coordinated with the finished-product details: welded seams, wire or ring reinforcement where required, end cuffs, handling straps, identification and packing.
A heavier fabric is not automatically the better confined space duct. Packed volume, bend flexibility, drag during setup, abrasion exposure, fan pressure and the number of deployment cycles can matter as much as nominal material weight. The practical goal is a construction that fits the intended system and crew workflow.
Collapsible supply duct
Typical role: positive-pressure fresh-air delivery where the fan inflates the duct during use.
Buyer priorities: low packed volume, simple handling, cuff security, abrasion protection around the entry opening and suitable section length.
Spiral wire-reinforced duct
Typical role: extraction, suction, reversible use, frequent bends or routes where the bore should retain shape.
Buyer priorities: wire pitch, bend radius, cuff strength, wear points, packing method and compatibility with negative static pressure.
Specification framework
Confined space ventilation duct specifications for RFQ planning
The table below is a purchasing framework, not a universal guaranteed datasheet. Final dimensions, construction and test values should be stated on the approved quotation, sample and technical documents.
| Product form | Finished flexible confined space ventilation duct / portable blower hose assembly. |
|---|---|
| Body construction | Polyester technical textile with PVC coating on both sides; exact base textile and formulation selected by duty and required test method. |
| Structure options | Collapsible positive-pressure construction; spiral wire-reinforced extraction/suction construction; project-specific reinforced format. |
| Common blower sizes | 8 in, 12 in and 16 in are common portable-ventilation market references. Production should be confirmed from the measured blower outlet and attachment geometry. |
| Diameter | Standard and custom diameters can be evaluated against blower outlet, airflow requirement and access-opening constraints. |
| Length | Section length and total route length are project-defined. Handling weight, storage, bends and coupling frequency should be considered. |
| End connection | Drawstring cuff, clamp cuff, belt, ring, zipper or custom interface according to the blower and joining method. |
| Reinforcement | Optional helical wire or ring support where the operating mode requires shape retention; final wire size and pitch depend on the duct design. |
| Color / marking | High-visibility colors and OEM identification can be discussed, subject to confirmed formulation and order requirements. |
| Safety-related options | Flame-retardant and antistatic formulations can be developed when a named test method, target level and finished construction are defined. |
| Fabrication | Cutting, hot-air or high-frequency welding, seam reinforcement, cuff assembly, wire installation, straps/handling details and finished-product inspection as applicable. |
| Packaging | Compressed packing, carrying/storage bag, labels and OEM packing can be evaluated for distributor, rental-fleet and equipment-kit programs. |
Important: blower free-air CFM is not the same as delivered airflow at the end of an installed duct route. Duct length, diameter, bends, leakage and system resistance affect delivered airflow and should be reviewed by the responsible ventilation/safety professional.
Industrial applications
Where confined space blower ducting is commonly specified
The exact ventilation method depends on the hazard assessment and site program. These are common environments where portable flexible ducting may form part of the airflow system.
Tanks & Process VesselsFresh-air delivery or exhaust routing during inspection, cleaning, lining, coating and maintenance activities.
Manholes & SewersPortable air delivery into below-grade spaces where access openings and routing are limited.
Utility VaultsTemporary ventilation around electrical, telecommunications and infrastructure maintenance tasks.
Shipyards & CompartmentsFlexible routes for maintenance, fabrication and localized air movement in restricted ship spaces.
Silos & Storage SpacesProject-specific ducting for controlled-entry inspection or maintenance where the hazard plan calls for mechanical ventilation.
Industrial ShutdownsPortable ducts for temporary airflow where crews move between equipment rooms, vessels, pits or enclosed process areas.
Safety & compliance context
Ventilation ducting is one component of a confined-space entry system
For U.S. workplaces, OSHA's permit-required confined-space rules include conditions under which continuous forced-air ventilation is used. OSHA states that the air should be directed to the immediate areas where employees are or will be present, should continue until employees leave, and should come from a clean source that does not increase hazards.
The duct therefore should not be presented as a stand-alone safety guarantee. Atmosphere testing/monitoring, fan selection, ventilation rate, source-air location, electrical classification, rescue planning and the full entry program remain separate engineering and safety responsibilities.
Procurement note: “flame retardant,” “antistatic” or “conductive” should not be treated as interchangeable claims. If a project has a hazardous-location or grounding requirement, provide the exact standard, resistance target, system architecture and documentation requirement. The complete blower/duct/electrical system should be evaluated for the intended environment.
Procurement & customization
What to include in a confined space ventilation duct RFQ
A complete RFQ helps separate a workable blower-duct assembly from a hose that only matches on nominal diameter.
Technical inputs
- Blower make/model and outlet photo
- Measured outlet outside diameter
- Supply, extraction or reversible operation
- Airflow / static pressure data if available
- Duct diameter and total route length
- Bend quantity and approximate bend radius
- Space opening or manhole constraints
- Temperature and chemical exposure
- Required flame/static test method
Commercial & fabrication inputs
- Preferred section length
- Cuff, clamp, zipper or ring connection
- Handling straps or suspension points
- Color and printed identification
- Storage/carrying bag requirement
- Sample or approval process
- Inspection and document expectations
- Quantity and packing format
- Delivery country / destination
Why DERFLEX
Coated-fabric knowledge connected to finished duct fabrication
DERFLEX is positioned as a manufacturing-based supplier of industrial coated fabrics and finished flexible ventilation ducts. For confined-space programs, the useful advantage is the ability to coordinate the duct body with welding, reinforcement, cuffs, markings and project-defined test requirements.
Blower-interface review
Photos, dimensions or an existing sample can be reviewed so the cuff is developed around the actual equipment interface.
Structure by pressure mode
Layflat and reinforced architectures can be evaluated separately instead of treating every flexible hose as interchangeable.
OEM configuration
Color, identification, section length, connection and packing can be adapted for distributors, fan brands and project supply.
Material + fabrication control
The coated textile, seam process, reinforcement and fittings are considered as a finished assembly rather than isolated components.
Requirement-based claims
Fire or antistatic performance is discussed against the named test method and approved construction instead of broad category promises.
Project documentation
Drawings, samples, inspection points and agreed test documentation can be incorporated into the order specification when required.
Related DERFLEX resources
Continue specification work with related ventilation duct pages
These six internal resources support airflow-direction, reinforcement, flame-performance and custom connection decisions.
Flexible Ventilation DuctOverview of finished layflat, reinforced and custom duct systems.
Portable Ventilation DuctBlower-matched ducting for changing industrial and maintenance work zones.
Spiral Wire-Reinforced Ventilation DuctShape-retaining construction for suction, extraction, bends and equipment connections.
Layflat Positive-Pressure Ventilation DuctCollapsible duct architecture for forced-air supply routes.
Flame Retardant Ventilation DuctHow to specify fire-performance requirements by test method and finished construction.
Custom Ventilation Duct & AccessoriesReducers, bends, transitions, fan adapters and project-specific connection details.
Buyer FAQ
Confined space ventilation duct questions
What is a confined space ventilation duct?
A confined space ventilation duct is a flexible hose or duct section used with a mechanical blower or extractor to route air to or from a restricted work area such as a tank, manhole, utility vault, vessel or ship compartment. The correct duct depends on the fan, pressure direction, route and site requirements.
Should I use layflat or spiral wire-reinforced ducting?
Layflat ducting is commonly evaluated for positive-pressure fresh-air delivery because the blower pressure inflates the hose. For extraction or suction, a wire-reinforced structure is normally evaluated because it helps the duct retain its bore under negative pressure. Reversible-duty systems are also usually reviewed with reinforcement.
How do I match ducting to an 8-inch, 12-inch or 16-inch blower?
Send the fan model and measure the actual outlet outside diameter, usable clamping length, guard/flange geometry and any existing cuff. Nominal 8, 12 or 16 inch sizing is useful for orientation, but the measured interface is more reliable for production.
Can DERFLEX customize duct length, cuffs and storage bags?
Yes. Section length, diameter, drawstring or clamp cuffs, rings, zippers, handling details, printed identification and packing can be reviewed for distributor, project, rental-fleet or OEM requirements.
Can the duct be flame retardant or antistatic?
Optional flame-retardant and antistatic constructions can be developed when the required test method and target value are defined. These are different performance properties and should not be assumed to make a complete ventilation system suitable for a hazardous location.
Does a ventilation duct make a confined space safe to enter?
No product page should make that claim. Mechanical ventilation can be one control within a confined-space program, but safe entry depends on the applicable hazard assessment, atmospheric testing or monitoring, ventilation design, equipment classification, entry procedure, rescue planning and local regulatory requirements.
Send the blower outlet and airflow direction first.
DERFLEX can review duct architecture, diameter, section length, cuff, reinforcement, marking and project-defined safety-related material options for your confined space ventilation duct requirement.