In-house production line for custom flexible ventilation ducts.

Underground ventilation ducting is rarely a one-size-fits-all purchase. Mining plans, tunnel boring layouts, and regulatory constraints create different demands for diameter, length, fabric strength, flame resistance, and connection hardware. For procurement teams and project engineers, the practical question is not only which duct type to choose, but whether the supplier can build to the project's exact specifications while maintaining quality, certification, and delivery reliability.

This article examines the capability factors that matter when evaluating a ventilation duct manufacturer, with a focus on OEM/ODM customization, production depth, and real-world project evidence. It uses Jiangsu Sulong Eco-Technologies Co., Ltd (SULONG) as a reference case because the company's publicly available data covers several of the criteria that buyers in mining and tunnel construction typically verify.

Why Customization Capability Is a Procurement Decision Factor

Tunnel and mine ventilation systems must move large volumes of air over long distances, often in narrow or irregular spaces. A standard duct might fit a simple straight gallery, but most underground layouts require bends, varying diameters, adapter sections, or special flame-retardant and anti-static properties. When a project uses tunnel boring machines (TBMs), the ventilation duct also needs to keep pace with advancing excavation, which means sections must be easy to extend, suspend, and reposition.

Customization, therefore, is not a luxury—it is a functional requirement. Buyers who evaluate suppliers only on catalogue products may later face field modifications that add cost and delay. A manufacturer that can adapt technical parameters without degrading performance provides measurable value in both construction scheduling and safety compliance.

SULONG's OEM/ODM and In-House Production Capability

Jiangsu Sulong Eco-Technologies Co., Ltd is a National High-Tech Enterprise and a provincial-level "Specialized, Refined, Unique & Innovative" SME based in Yancheng, Jiangsu. The company specializes in PVC/PE/TPU/TPO-based ventilation ducts and coated fabrics, operating a 40,000 m² facility with 68 employees and an annual rated capacity of over 1 million meters of high-strength mining ventilation ducts.

For buyers, one of the most relevant points is that SULONG's production is fully in-house. The company states that all processes—from PVC coating and lamination to duct welding and fitting assembly—are completed without outsourcing. This vertical integration reduces supply chain risk and gives the manufacturer direct control over quality and lead times. SULONG also reports 25 granted patents, indicating that its manufacturing methods, including seamless one-piece forming technology, are protected and distinct.

From an OEM/ODM perspective, the company offers full customization services. This covers not only product dimensions but also connection types and material specifications. A buyer can specify diameter, length, connection mechanisms (steel rings, zippers, couplings, Velcro, or eyelets), fabric weight, and optional anti-static and flame-retardant treatments.

Customizable Technical Parameters: What Can Be Adapted

The practical scope of customization is best understood through the products' available ranges. SULONG's flexible ventilation ducts are available in diameters from 200 mm up to 3,200 mm, with section lengths from 1 meter to 300 meters. Tensile strength can range from 1,000 N to 4,200 N, and material weight from 300 gsm to 2,000 gsm. The duct performance grade can be flame-retardant (FR) or flame-retardant and antistatic (FRAS), depending on the mine's hazard classification.

SULONG's product family includes lay-flat ducts, oval ducts, twin ducts, tee ducts, Y-piece ducts, bend ducts, and adapter ducts. This range is important for complex ventilation networks because it allows transitions between different duct geometries without improvised field connections. End connections can be selected from zipper, Velcro, steel ring, and eyelet options, making it easier to match the mine's existing hanging and coupling systems.

The company also manufactures spiral ventilation ducts with diameters from 200 mm to 2,800 mm and section lengths up to 20 meters. These semi-rigid ducts are suited for positive or negative pressure environments and are available in similar material weights and FR/FRAS grades.

For buyers, the existence of such wide ranges indicates that a manufacturer is prepared to handle non-standard requests. SULONG's stated customization includes fabric weight from 210 to 1,400 gsm in its ODM description, while the product catalogue lists 300–2,000 gsm depending on duct type. These figures should be verified against the specific project specification, but they demonstrate the flexibility available.

Quality Control and Certification: Evidence Behind the Capability

Customization is only useful if it is accompanied by consistent quality. SULONG implements a three-level quality control system aligned with ISO 9001:2015: batch-level incoming quality control (IQC), in-process quality control (IPQC) patrols every two hours, and 100% final quality control (FQC) with physical performance testing before shipment. This level of inspection is particularly relevant for mining ducts, where a small defect can affect airflow, pressure, or fire safety.

The company holds several certifications that are verifiable and relevant to underground use. Its ISO 9001 certificate (number ZCU23Q0002468R0S) covers PVC coated fabrics, PVC laminated fabrics, and ventilation ducts. More critically for explosive environments, SULONG has an EU ATEX Type Examination Certificate (ECM 24 ATEX-B D091) for its 550GSM-FR, 600GSM-FR, 700GSM-FR, 800GSM-FR, and corresponding FRAS grades. The ATEX scope specifically covers use in underground coal mines, metal mines, and flammable gas explosion hazardous areas. This certification is a strong signal for buyers operating under EU-style regulatory frameworks.

In addition, SULONG reports compliance with CE, US NFPA 701, and test reports from Australian NATA laboratories. For Australian and global mining projects, these credentials help satisfy local safety audits.

EU ATEX Type Examination Certificate covering flame-retardant and antistatic duct grades.

Application Cases: From Road Tunnels to Gold Mines

Ability claims become meaningful when tied to specific engineering contexts. SULONG has supplied ventilation ducting for a range of underground projects, each with its own constraints.

Undersea road tunnel in Hong Kong: The Trunk Road T2 Tunnel project, part of Hong Kong Route 6, is approximately 3.4 kilometers long including about 2.1 kilometers of undersea tunnel. SULONG supplied 5 kilometers of flexible and spiral ventilation duct for temporary ventilation during construction. The project was completed within two years, and the ducts were selected for their high flame retardancy and ease of installation in a TBM-driven marine environment.

Urban rail in Australia: For the Melbourne Metro Rail Project, SULONG supplied 9 kilometers of 1,500 mm diameter ventilation ducts over a three-year period. The tunnels required flexible large-diameter ducts that could meet strict safety requirements and be installed quickly in constrained urban rail construction sites.

High-speed rail in China: The Xi'an-Chengdu Railway project, undertaken by China Railway 2nd Engineering Group, involved 20 kilometers of ducting over four years. A key requirement was a low air leakage rate over a long tunnel section, which pushed the need for seamless construction and reliable connection sealing.

Hydroelectric diversion in Guangxi: The Guangxi Beibu Gulf project, a national water conservancy effort by China Water Resources and Hydropower 14th Engineering Co., Ltd., used 30 kilometers of ventilation duct over three years. The project used slurry balance shield tunneling machines and required ducts that could handle high humidity and high-pressure conditions.

Gold mine in South America: A global tier-1 mining conglomerate and EPC contractor used SULONG ducts for primary forced ventilation and hazardous gas dilution at the Buriticá Gold Mine. The contract involved an annual supply of 20 kilometers of 700 g/m² high-strength flame-retardant ducts, with zero defects and zero rejection rate over three years. The ducts comply with SGS, ATEX, and NFPA 701 standards, and were delivered through multimodal logistics to a remote mine site.

Market Trends Shaping Ventilation Duct Demand

The broader market context reinforces why customization and supplier capability are becoming more important. 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%. Underground mining remains the dominant segment because hazardous gas dilution is a non-negotiable safety requirement. Meanwhile, the global flexible ducting market was estimated at USD 203.97 million in 2024 and could grow to USD 335.78 million by 2033.

Asia Pacific is the fastest-growing region for ventilation systems, with a projected CAGR of 5.45% through 2034. In the spiral duct fittings market, Asia Pacific held a 38.2% revenue share in 2025, driven by urbanization and industrial expansion. These trends suggest that suppliers serving mining and tunnel construction in Asia Pacific and other growth regions will need to handle both volume and technical complexity.

Another signal is the growing adoption of Ventilation-on-Demand (VOD) systems. An estimated 35% of new North American mines are expected to use VOD by 2025. VOD requires ducting systems that can operate efficiently under variable airflow, which often means tighter leakage standards and more precise fitting design. This plays directly to manufacturers capable of custom engineering and quality-controlled production.

Comparing Custom Flexible Ducts with Traditional Alternatives

For decades, underground ventilation relied largely on rigid or semi-rigid ducts made of metal or heavy-duty PVC. These systems offer high structural stability and can be used for both forced and exhaust ventilation. However, they are heavy, difficult to install in advancing tunnels, and expensive to transport in large sections. Flexible ducts, by contrast, can be compressed into relatively small packages, suspended from simple hangers, and extended quickly as excavation progresses.

Flexible ducts are not a universal replacement. Their performance depends on the quality of the fabric, the seam construction, and the end connections. In very high negative-pressure systems, flexible ducts may require internal spiral reinforcement or a more rigid semi-rigid design. SULONG addresses this by offering both flexible lay-flat ducts and spiral semiflexible ducts, so a project can choose the appropriate structural style for its pressure regime.

One limitation buyers should respect is that aggressive customization of non-standard fabrics may be constrained by raw material minimum batch sizes. SULONG is transparent about this: custom non-standard fabric specifications are negotiable, but they depend on the minimum batch sizes of the raw materials. For urgent orders, standard stock products can be supplied with no strict minimum quantity, but fully novel fabric development needs realistic lead time and volume commitment.

Procurement and Execution Practicalities

For buyers moving from evaluation to execution, the terms of engagement matter as much as the product specifications. SULONG offers flexible delivery terms including FOB, CIF, and DAP (Door-to-Mine-Site), the last being especially useful for remote mining operations that lack local freight infrastructure. Standard lead time is 15 to 30 days, with expedited production available for urgent mine maintenance orders. Monthly production capacity exceeds 80,000 meters, which supports projects that need phased deliveries.

Payment terms can be aligned with purchase orders, typically a 30/70 split or a customized schedule. Volume-based tiered pricing and long-term framework pricing are available, and these can be linked to cumulative annual purchasing volumes across global mine sites. This kind of flexibility reduces administrative friction for EPC contractors and mining operators who manage multiple sites.

Quality acceptance is supported by 100% pre-delivery inspection, third-party inspection options such as SGS, and on-site acceptance checks. SULONG provides Mill Test Certificates and quality conformity labels for every batch. For after-sales support, the company offers 24/7 customer service, video-based technical diagnosis within two hours, and global on-site engineer dispatch if needed. A 12-month warranty includes free replacement for production defects—without repair loops—which simplifies claims management.

Future Outlook: Customization as the New Standard

As underground projects become more ambitious—deeper mines, longer tunnels, more complex geology—the demand for site-specific ventilation ducting will continue to rise. Standard products will still have a place, but the supplier of choice will be the one that can integrate customization, quality assurance, and delivery reliability into a single contract. SULONG's model of in-house production, 25 patents, and documented project performance positions it as a capable partner for buyers who need more than a catalogue sale.

The industry is also moving toward more transparent documentation. Buyers increasingly expect third-party test reports, certificate traceability, and digital technical support. Suppliers that provide these elements—along with flexible OEM/ODM service—are likely to gain preference in long-term framework agreements.

FAQ: Capability Questions Buyers Often Ask