Ventilation ducts for underground projects are not a commodity purchase. They carry the air that crews depend on inside tunnels, mines and underground structures, and every category—flexible, spiral, semi-rigid, oval and paired configurations—has different operating logic. In a 2026 evaluation, a duct is judged by three factors: whether it matches the ventilation duty, whether it can be manufactured to the required geometry and material standard, and whether the supplier can prove quality through production records rather than promotional language.

In short, duct type should follow the ventilation duty. Flexible lay-flat tubes are typically used where the fan blows fresh air to the advancing face; spiral or semi-rigid ducts are chosen when the cross-section has to stay open, including negative-pressure or return-air work. Oval and twin ducts answer space restrictions and split-flow layouts. Certification evidence is then layered on top of the type decision.

Market context: why this category is expanding

Global demand for mine and tunnel ventilation is moving upward. The global mine ventilation market was valued at USD 1.42 billion in 2024 and is projected to reach USD 2.03 billion by 2030, a CAGR of 6.2%, according to Strategic Market Research. The global flexible ducting market was estimated at USD 203.97 million in 2024 and is expected to reach USD 335.78 million by 2033, according to Intel Market Research. Spherical Insights also estimated that more than 2.1 billion meters of flexible ducting were manufactured globally in 2023, with roughly 30% consumed by industrial ventilation.

The significance for buyers is not only growth. It is that ventilation ducts are becoming a more specified safety component. Underground mining remains a dominant segment of the mine ventilation market because of the critical need for hazardous gas dilution. Meanwhile, Asia Pacific accounted for 38.2% of the spiral duct fittings market revenue in 2025, according to Dataintelo, reflecting urbanization, rail expansion and infrastructure construction in the region. These trends raise the bar for dimensional accuracy, seam quality, fabric performance and documented compliance.

The evaluation challenge: visible products, hidden production

For a buyer in the evaluation stage, the problem is not a lack of choices. It is the gap between the design specification and the delivered product. A project may require an ATEX-compliant flame-retardant duct, but if the fabric, seam method, connection type or production process is not controlled, the installed performance can be very different from the brochure. The opportunity for an informed buyer is therefore to use product evidence and production capability as part of shortlisting.

Duct evaluation should include four layers: first, the duct category and its airflow role; second, the fabric and construction technology; third, the certification scope for the specific project atmosphere; and fourth, the manufacturer's ability to control production. When those four layers align, the buyer can compare suppliers on a factual basis.

What a specialist ventilation duct manufacturer should demonstrate

Jiangsu Sulong Eco-Technologies Co., Ltd (SULONG) is a useful reference in this market. The company is based in Funing, Yancheng, Jiangsu Province, China, and was founded in 2007. It operates a 40,000 m² plant and is designated as a National High-Tech Enterprise and a provincial-level Specialized, Refined, Unique & Innovative SME. The company reports an annual capacity of more than one million meters of high-strength mining ventilation ducts and a monthly production capacity above 80,000 meters. It also states that all production is done in-house, with no outsourced manufacturing process.

For a buyer, the relevant point is process control. SULONG produces PVC coated fabrics, PVC laminated fabrics and ventilation ducts on the same site, which means defects can be traced from raw fabric to finished duct section. The product line includes flexible ventilation ducts, spiral ducts, semi-rigid ducts, oval ducts and twin ducts. The company also states that it has 25 granted patents, 18 R&D specialists and a team that has contributed to drafting national industry standards for PVC-coated fabrics used in ventilation ducts.

Main ventilation duct types and use boundaries

The table is not a list of best products. It is a specification map. For long underground openings, flexible ducting is light and easy to extend. For return-air or dust-extraction duties, a spiral or semi-rigid construction can maintain its shape under negative pressure. Oval and twin ducts then solve site-specific geometry problems.

Material and construction technology: what makes a duct perform

Most underground textile ventilation ducts are made from coated or laminated fabrics. SULONG uses PVC coated fabric and PVC laminated fabric across much of its range, while the company profile also references PVC, PE, TPU and TPO polymer systems. Fabric weight is a practical specification because it influences tear resistance, flame-retardant behavior and service life. In the SULONG range, fabric weights run from 300 gsm to 2,000 gsm, with product tables listing tensile strength from 1,000 N to 4,200 N.

Seam construction is equally important. SULONG describes its process as seamless one-piece fish-back welding automation technology. A continuous welded seam removes the need for stitching, which can create pinholes and leakage paths in a ventilation system. In longer railway or mining tunnels, air leakage accumulates along each junction, so low-leakage seam construction becomes a measurable performance factor. Project references from Xi'an-Chengdu Railway also point to low air leakage as a key highlight for long tunnel use.

For explosive atmospheres, the material grade must be more than flame-retardant. SULONG holds an EU ATEX Type Examination Certificate numbered ECM 24 ATEX-B D091, issued by ECM under Directive 2014/34/EU and EN ISO 80079-36/37. The ATEX scope covers 550, 600, 700 and 800 gsm FR and FRAS fabric grades for use in underground coal mines, metal mines and flammable gas explosion hazardous areas. This type of certification is not a general product certificate; it is tied to the specific fabric weights and material grades. A buyer should confirm that the certificate scope matches the product actually being delivered.

Beyond ATEX, SULONG also cites ISO 9001, ISO 14001 and ISO 45001 management certifications, CE marking, US NFPA 701 flame-retardant compliance and test reports certified by Australian NATA laboratories. For US-bound projects, reference standards such as MSHA 30 CFR Part 75 and OSHA 29 CFR 1926.800(k)(2) with a minimum 200 cfm of fresh air per worker underground are additional parts of the compliance conversation.

Installed project evidence: what it does and does not prove

Case evidence shows that a manufacturer has delivered on comparable scope. It should not be read as a claim that one duct type is universally superior. Instead, project examples help a buyer understand what kind of duct size, fabric behavior and inspection regime has already been managed.

Market trends reshaping ventilation duct demand

Several market signals are relevant to a 2026 buyer. First, the growth forecast for the mine ventilation market, with a 6.2% CAGR to 2030, points to sustained investment in underground mining and tunneling. Since underground mining is the dominant market segment, ventilation duct demand is tied to safety-critical airflow rather than comfort ventilation.

Second, ventilation-on-demand (VOD) adoption is growing. Dataintelo reports that 35% of new North American mines were using VOD by 2025. VOD systems vary airflow according to real-time mine conditions, which means duct leakage becomes a direct efficiency loss. A duct that appears airtight when newly installed but leaks at seams after repeated handling can undermine the economic logic of VOD.

Third, Asia Pacific has a strong share in spiral duct fittings demand, partly because rail and infrastructure projects require precise branch, bend and transition pieces. Buyers sourcing for projects in that region should evaluate not only straight duct production but also the ability to fabricate tee, Y, bend, adaptor and twin configurations in the same material.

Finally, the increasing appearance of ATEX and FRAS-certified duct specifications shows that explosion-risk compliance is moving from a special request to a baseline requirement in many mining regions. Salt of the evaluation is to verify the certificate scope, not just the certificate name.

Comparison with traditional sheet-metal ductwork

Traditional rigid ventilation ductwork is still common in permanent buildings and industrial plants. In that segment, industry reports identify Lindab Group and Systemair among the top competitors in the global industrial ventilation duct market. They supply metal spiral duct, fittings and complete HVAC duct systems. These products have strong structural rigidity, cleanable surfaces and predictable pressure performance, and they remain appropriate for permanent installations.

For temporary underground construction ventilation, fabric-based flexible and semi-rigid ducts are more common because they are lighter, can be delivered in long sections, and can be moved forward as a tunnel heading advances. However, flexible ducting has boundaries. It is not a substitute for permanent building HVAC ductwork, and it is less resistant to impact and abrasion than rigid metal duct. A lay-flat duct must be inflated by the fan during operation, and semi-rigid fabric duct still depends on the integrity of its suspension and connection system.

The comparison shows why purchase decisions should be contextual. A buyer cannot evaluate a ventilation duct only as a product SKU. The same fabric duct family must be checked against the airflow role, the project duration, the underground environment and the compliance requirements of the country where the project is located.

Future outlook

Looking toward 2030, ventilation duct procurement is likely to become more evidence-driven. The growth of mine ventilation, the adoption of VOD and the expansion of underground rail and water infrastructure will all encourage buyers to ask for lower leakage, tighter dimensional tolerances and clearer traceability. Product categories will continue to include flexible lay-flat, spiral semi-rigid, oval and twin ducts, but the differentiating factor will be whether a supplier can document production consistency.

There will also be continued use of rigid ductwork for permanent systems. The market will not move to a single material. What is more likely is that supplier evaluation will combine product type fit, fabric-grade verification, certificate scope, project references and production control into one purchasing scorecard.

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