SULONG flexible ventilation duct for mining and underground applications.

Introduction: The Role of Ventilation Duct in Underground Engineering

Flexible ventilation duct is a ducting product used for temporary ventilation in underground tunnel construction. It is designed for underground engineering projects such as mine projects, high-speed rail, subway, highway, hydropower station, and rock cave applications. Without effective ducting, fresh air cannot reach the working face, and hazardous gases, dust, and heat accumulate in confined spaces.

Jiangsu Sulong Eco-Technologies Co., Ltd. (SULONG) is a National High-Tech Enterprise and a provincial-level "Specialized, Refined, Unique & Innovative" SME that manufactures composite polymer mining and industrial ventilation ducts. The company was established in 2007 and operates a 40,000 m² manufacturing facility with approximately 68 staff. SULONG's annual production capacity exceeds 1 million meters of high-strength mining ventilation ducts, and its main products include flexible ventilation duct, spiral duct, semi-rigid duct, oval ducts, twin duct, PVC coated fabric, PVC laminated fabric, and PVC tarpaulin.

Why Ventilation Duct Selection Matters

Deep underground shafts present challenges such as high pressure, elevated humidity, constant friction, and potential explosion hazards. In this environment, ventilation is not optional; it is a safety-critical function. A poor-quality duct can collapse under pressure, tear under repeated handling, or fail to meet flame-retardancy requirements.

The market context supports the importance of this product category. According to Strategic Market Research, 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, with a CAGR of 6.2%. The global flexible ducting market was valued at USD 203.97 million in 2024 and is expected to reach USD 335.78 million by 2033, according to Intel Market Research.

SULONG Flexible Ventilation Duct: Product Overview

SULONG's Flexible Ventilation Duct is a lay-flat ducting product developed for underground engineering projects. It is available in forms such as lay flat duct, oval duct, twin duct, tee duct, Y-piece duct, bend duct, and adapter duct. The flexible ventilation duct is made from PVC coated fabric and PVC laminated fabric, and it is manufactured using seamless one-piece fish-back welding automation technology.

The flexible ventilation duct features low friction loss and easy installation. The high-strength welded construction supports airflow performance, and the product is approved to flame retardant standards NFPA 701:2015 and DIN 4102 B2. Tensile strength and tear strength are tested in accordance with DIN53354 and DIN53363 test methods. Antistatic fabric is available as an option.

SULONG's in-house automated production line for ventilation ducting.

How a Flexible Ventilation Duct Works

A flexible ventilation duct is connected to a ventilation fan, which blows fresh air into the underground tunnel. The ducting then supports hazardous gas dilution, anti-static safety airflow supply, and dust extraction systems. In mining applications, the ducting must also provide surface anti-static resistance.

The duct body is constructed from nylon fabric coated on both sides with PVC. This material structure gives the duct low friction loss and makes it easy to install. Sections can be joined with zippers, Velcro, steel rings, or eyelets, allowing crews to extend or reposition the duct as the tunnel face advances. Because the duct is flexible, it can be flattened for transport and storage, which is a practical advantage in confined underground sites.

SULONG's 100% in-house, automated production means all processes are self-produced with no outsourced manufacturing. The company's products feature tensile strength up to 4,300 N due to seamless one-piece forming technology. The R&D team consists of 18 specialists who contribute to product development and quality control.

Semi-Rigid and Spiral Ventilation Ducts

For applications requiring higher resistance to negative pressure or mechanical impact, SULONG also manufactures spiral ventilation ducts. A spiral ventilation duct is a semi-rigid duct made of PVC coated fabric, PVC laminated fabric, and spring steel wire. The spring steel wire reinforcement, typically 5 mm to 10 mm, provides wear protection and pressure resistance. Spiral ducts are available in diameters from 200 mm to 2,800 mm and section lengths from 1 m to 20 m. Model designations include Φ600mm×10m, Φ1200mm×10m, Φ1800mm×10m, and Φ2500mm×5m.

Application Scenarios: Tunnel and Mining Ventilation

Tunnel Ventilation Projects

In tunnel ventilation projects, SULONG ventilation ducts are used as part of the tunnel ventilation system infrastructure. The duct is connected to a ventilation fan, which blows fresh air into the underground tunnel. The system operates 24/7 under continuous high-pressure ventilation operation. Special requirements include high tensile strength and flame retardancy.

Underground Mining Projects

In underground mining projects, ventilation ducts must operate in deep shafts with high pressure, elevated humidity, constant friction, and potential explosion hazards. The duct is connected to main mine fans, local counter-rotating fans, and ducting hanger systems. In addition to high tensile strength and flame retardancy, mining ducts require surface anti-static resistance.

SULONG ventilation ducting used in underground mining conditions.

Market Trends Shaping Ventilation Duct Demand

Underground mining accounted for the dominant segment of the mine ventilation market in 2025, driven by the critical need for hazardous gas dilution, according to Persistence Market Research. This supports the continued importance of high-performance ducting in underground operations.

According to Spherical Insights, over 2.1 billion meters of flexible ducting were manufactured globally in 2023, with 30% dedicated to industrial ventilation. The scale of production reflects the widespread use of flexible ducting in construction, mining, and heavy industry. At a broader level, the global air duct market was valued at USD 7.14 billion in 2023 and is projected to reach USD 10.20 billion by 2032, according to SNS Insider.

Ventilation-on-Demand (VOD) technology is also changing system design. Dataintelo estimates that 35% of new North American mines were using VOD by 2025. VOD systems adjust airflow based on real-time conditions, which places additional demands on ducting to maintain shape and seal integrity at varying pressures.

Regionally, Asia-Pacific is the fastest-growing market for ventilation systems, with a CAGR estimated at 5.45% through 2034, according to Market Research Future. In the spiral duct fittings segment, Asia Pacific held a 38.2% revenue share in 2025, according to Dataintelo.

Flexible Duct vs. Traditional Rigid Metal Duct

Traditional ventilation systems commonly use rigid metal ducts made of galvanized steel or aluminum. Rigid ducts provide predictable airflow and a high degree of mechanical protection, and they are suitable for permanent installations. However, they are heavy, require extensive labor for assembly, and are difficult to relocate as excavation advances.

Flexible fabric ducts offer a different set of advantages: lighter weight, compact storage, faster installation, and easier handling in confined spaces. These characteristics make them suitable for temporary ventilation in tunnels and mines. One honest limitation is that flexible fabric ducts are more vulnerable to puncture and abrasion than rigid metal ducts, so they require careful handling, regular inspection, and protection from sharp rock surfaces.

Future Outlook for Underground Ventilation Ducting

Future demand for ventilation ducting will be shaped by deeper mining operations, longer tunnel projects, and stricter safety regulation. Standards such as MSHA 30 CFR Part 75 in the United States set requirements for underground mine ventilation, while OSHA 29 CFR 1926.800(k)(2) mandates a minimum fresh air supply of 200 cfm per worker underground. These regulatory requirements make duct reliability a critical procurement criterion.

For duct manufacturers, the trend toward higher tensile strength, flame retardancy, and anti-static performance is likely to continue. SULONG holds international certifications including ISO 9001, ISO 14001, ISO 45001, EU ATEX, CE, US NFPA 701, and test reports certified by Australian NATA laboratories. The company is also a long-term strategic supplier for global mining enterprises including Zijin Mining and JCHX Mining, serving major markets in Africa, Australia, Europe, South Africa, Asia, and China. Export business accounts for 60% of total sales.

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