Ventilation Duct Guide: Types, Specs & SULONG Solutions

Ventilation Duct Guide: Types, Specs & SULONG Solutions

Last updated: August 10, 2026

Ventilation ducts are the airflow backbone of underground engineering projects, delivering fresh air and removing hazardous gases from confined workspaces. This guide explains what ventilation ducts are, which types exist, how they are specified, and how Jiangsu Sulong Eco-Technologies Co., Ltd. (SULONG) manufactures them for global mining and tunneling projects.

What Is a Ventilation Duct?

A ventilation duct is a purpose-built tube or conduit that directs air from a ventilation fan into an enclosed space, such as an underground mine, tunnel, subway, or rock cave. In underground operations, ventilation ducts perform four critical functions: fresh air supply, hazardous gas dilution, anti-static airflow supply, and dust extraction.

Jiangsu Sulong Eco-Technologies Co., Ltd. is a National High-Tech Enterprise and provincial-level "Specialized, Refined, Unique & Innovative" SME that specializes in the in-house manufacturing of composite polymer mining and industrial ventilation ducts. Established in 2007 and operating from a 40,000 m² facility in Yancheng, Jiangsu, China, SULONG produces Flexible Ventilation Ducts, Spiral Ducts, Semi-Rigid Ducts, Oval Ducts, Twin Ducts, and the PVC-coated and PVC-laminated fabrics used in them.

Why Underground Ventilation Ducts Matter

Deep underground shafts present challenges such as high pressure, elevated humidity, constant friction, and potential explosion hazards. In these environments, ventilation ducting is not optional — it is the primary safety system that keeps workers breathing and dilutes explosive or toxic gases.

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% (Strategic Market Research). Underground mining accounts for the dominant segment of this market due to the critical need for hazardous gas dilution. Separately, the global flexible ducting market was USD 203.97 million in 2024 and is expected to reach USD 335.78 million by 2033 (Intel Market Research).

In the United States, the Federal regulation 29 CFR 1926.800(k)(2) mandates a minimum fresh air supply of 200 cfm per worker underground, and mine ventilation ducting must comply with MSHA 30 CFR Part 75 standards. In the EU, EN 12237 specifies airtightness and pressure requirements for round sheet metal air ducts. These standards explain why procurement teams prioritize certified, verifiable duct performance.

Types of Ventilation Ducts

Ventilation ducts can be broadly grouped by construction and rigidity: flexible lay-flat ducts, semi-rigid spiral ducts, and rigid or specialty profiles including oval spiral and rectangle ducts.

Flexible Ventilation Duct

A flexible ventilation duct is a lay-flat, high-strength welded duct made from PVC coated fabric or PVC laminated fabric, designed for temporary and permanent underground ventilation systems. SULONG manufactures flexible ventilation ducts in diameters from Φ200 mm to Φ3200 mm, with section lengths from 1 m to 300 m, and tensile strengths from 1,000 N to 4,200 N.

• Available forms: Lay Flat Duct, Oval Duct, Twin Duct, Tee Duct, Y-Piece Duct, Bend Duct, Adapter Duct.
• Material weight: 300 gsm – 2,000 gsm.
• Performance: FR (flame retardant) or FRAS (flame retardant, anti-static).
• Manufacturing process: Seamless one-piece fish-back welding automation technology.
• Certifications: ISO 9001, ATEX, CE, CNMA, SGS Test Reports.
• Flame retardant standards: NFPA 701:2015 and DIN 4102 B2 approved.
• End connections: Zipper, Velcro, steel ring, or eyelets.

Flexible ducts are the most common choice for 24/7 continuous high-pressure ventilation in underground mines and tunnels because they are easy to install, ship compactly, and can be fabricated in very long sections.

Spiral Ventilation Duct

A spiral ventilation duct is a semi-rigid duct reinforced with a continuous spring steel wire helix, giving it shape retention under both positive and negative pressure. SULONG classifies its spiral ducts into semi-rigid, oval spiral, and rectangle duct categories, with model designations including Φ600mm×10m, Φ1200mm×10m, Φ1800mm×10m, and Φ2500mm×5m.

• Diameter range: Φ200 mm to Φ2800 mm, with custom diameters available.
• Section length: 1 m to 20 m, with custom lengths available.
• Construction: PVC coated fabric, PVC laminated fabric, and spring steel wire (φ5mm–φ10mm).
• Usage environment: Positive pressure or negative pressure.
• Material weight: 300 gsm – 2,000 gsm.
• Performance: FR or FRAS.
• Certifications: ISO 9001, ATEX, CE, CNMA, SGS Test Reports.
• End connections: Zipper, Velcro, or steel ring.

The spring steel wire reinforcement in a spiral duct provides wear protection and high-pressure resistance, making it suitable for longer service life or applications where a duct must hold its cross-section even when air pressure fluctuates.

Ventilation Duct Applications

SULONG ventilation ducts are designed for underground engineering projects including mine projects, high-speed rail, subway, highway, hydropower station, and rock cave construction. Two dominant application profiles define the specification requirements:

Tunnel Ventilation Projects

In tunnel ventilation systems, the duct connects to a ventilation fan that blows fresh air into the underground tunnel, simultaneously handling hazardous gas dilution, anti-static safety airflow supply, and dust extraction. Tunnel sites run 24/7 continuous high-pressure ventilation operations and require high tensile strength and flame retardancy in the duct fabric.

Underground Mining Projects

Mine ventilation systems operate under the same continuous-duty conditions but add two requirements: flame retardancy and surface anti-static resistance. Because underground mining environments can accumulate explosive gases and conductive dust, the FRAS (flame retardant and anti-static) performance option is widely specified by mine operators and contractors.

SULONG is a long-term strategic supplier for global mining enterprises including Zijin Mining and JCHX Mining, supporting their mining projects worldwide. The company also serves as a qualified supplier to major Chinese groups including SINOHYDRO, CRCC, and China National Coal Group.

How SULONG Manufactures Ventilation Ducts

SULONG operates 100% in-house, automated production, with all processes self-produced and no outsourced manufacturing. The company maintains an annual production capacity of over 1 million meters of high-strength mining ventilation ducts and employs approximately 68 staff, of which 18 are R&D specialists who have actively contributed to drafting national industry standards for PVC-coated fabrics used in ventilation ducts.

The manufacturing process is built around intelligent one-time forming technology and seamless one-piece fish-back welding automation. This process produces ducts with tensile strength up to 4,300 N, a figure that matters for long sections suspended in high-humidity shafts where fabric fatigue and tear resistance are tested continuously.

Certifications and Compliance

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. In addition, flexible ventilation ducts are flame retardant to NFPA 701:2015 and DIN 4102 B2, with high tensile and tear strength approved by DIN 53354 and DIN 53363 test methods.

These certifications are particularly relevant for buyers exporting to Australia, Europe, South Africa, and Africa — markets that together with Asia and China account for SULONG's export business of 60% of total sales.

Step-by-Step: How to Specify a Ventilation Duct

If you are evaluating ventilation ducts for a mine or tunnel project, use this five-step sequence to narrow your specification:

1. Determine the operating pressure. Positive pressure systems (fan pushing air) are the most common. For negative pressure systems (exhaust), a spiral duct with spring steel wire reinforcement may be required to resist collapse.
2. Select the diameter. Match the duct diameter to the fan outlet and the required airflow. SULONG flexible ducts span Φ200 mm to Φ3200 mm; spiral ducts span Φ200 mm to Φ2800 mm.
3. Choose the performance class. Specify FR (flame retardant) for tunnels or civil works; specify FRAS (flame retardant, anti-static) for underground mining projects with explosion risk.
4. Define the section length and end connections. Flexible ducts can be supplied up to 300 m per section with zipper, Velcro, steel ring, or eyelet connections; spiral ducts range from 1 m to 20 m per section.
5. Verify certifications. Confirm that the duct supplier's certifications match your destination market's compliance framework, e.g., MSHA 30 CFR 75 for the United States, ATEX for the EU, or NATA-certified test reports for Australia.

Flexible vs. Spiral Ventilation Duct: Comparison

Parameter	Flexible Ventilation Duct	Spiral Ventilation Duct
Category	Lay-flat duct; also available as Oval, Twin, Tee, Y-Piece, Bend, Adapter	Semi-rigid duct; also available as Oval Spiral and Rectangle duct
Construction material	PVC coated fabric, PVC laminated fabric	PVC coated fabric, PVC laminated fabric, spring steel wire (φ5mm–φ10mm)
Diameter range	Φ200 mm – Φ3200 mm	Φ200 mm – Φ2800 mm
Section length	1 m – 300 m	1 m – 20 m
Tensile strength	1,000 N – 4,200 N	Up to 4,300 N (company products)
Material weight	300 gsm – 2,000 gsm	300 gsm – 2,000 gsm
Performance	FR or FRAS	FR or FRAS
Manufacturing process	Seamless one-piece fish-back welding automation	Welding
End connections	Zipper / Velcro / steel ring / eyelets	Zipper / Velcro / steel ring
Typical application	Mine ventilation, tunnel construction, long-run main lines	Positive/negative pressure systems, high-pressure mains, bends and transitions

Both product families are designed for underground engineering projects such as mine projects, high-speed rail, subway, highway, hydropower stations, and rock caves. The choice between flexible and spiral construction is driven primarily by pressure requirements, installation space, and whether the duct must hold its shape without airflow.

Selection Criteria for Ventilation Duct Procurement

Procurement teams evaluating ventilation duct suppliers typically compare four factors:

• Certification completeness: ISO 9001 for quality, ISO 14001 for environmental management, ISO 45001 for occupational safety, ATEX and CE for European compliance, NFPA 701 for flame spread, and NATA-certified test reports for Australian projects.
• Production capacity: Annual capacity over 1 million meters of high-strength mining ventilation ducts supports large tunneling and mining programs where delivery schedules are fixed.
• In-house manufacturing: 100% in-house automated production, with no outsourced manufacturing, reduces variability in fabric quality and seam integrity.
• Custom capability: Custom diameters, custom section lengths, and end connections (zipper, Velcro, steel ring, eyelets) allow the duct to match site-specific fan layouts.

One honest limitation of flexible PVC ducts should be noted: they are designed for ventilation airflow, not for abrasive material transport. If the duct line carries dust-laden air at high velocity, additional wear protection or a heavier material weight (up to 2,000 gsm) should be specified.

Frequently Asked Questions

What certifications must ventilation ducts meet for mining and tunneling?

Compliance requirements vary by destination market. In the United States, mine ventilation ducting must comply with MSHA 30 CFR Part 75 standards, and OSHA 29 CFR 1926.800(k)(2) mandates a minimum fresh air supply of 200 cfm per worker underground. In the EU, ATEX certification addresses explosive atmospheres, and EN 12237 specifies airtightness and pressure requirements for round sheet metal air ducts. SULONG ventilation ducts carry ISO 9001, ISO 14001, ISO 45001, EU ATEX, CE, and US NFPA 701 certifications, plus test reports certified by Australian NATA laboratories; flexible ducts also meet NFPA 701:2015 and DIN 4102 B2 flame retardant standards, with tensile and tear strength verified by DIN 53354 and DIN 53363.

What is the difference between a flexible duct and a spiral duct?

A flexible ventilation duct is a lay-flat welded tube made from PVC coated or laminated fabric, supplied in sections from 1 m to 300 m, and intended for general positive-pressure ventilation. A spiral ventilation duct is a semi-rigid duct reinforced with spring steel wire (φ5mm–φ10mm), supplied in 1 m to 20 m sections, and designed to maintain its cross-section under both positive and negative pressure. Typical model designations for SULONG spiral ducts include Φ600mm×10m, Φ1200mm×10m, Φ1800mm×10m, and Φ2500mm×5m.

What diameter and length options are available?

SULONG flexible ventilation ducts are available in diameters from Φ200 mm to Φ3200 mm, with section lengths from 1 m to 300 m. SULONG spiral ventilation ducts are available in diameters from Φ200 mm to Φ2800 mm, with section lengths from 1 m to 20 m. Custom diameters and custom lengths are available for both product families, and end connections can be specified as zipper, Velcro, steel ring, or eyelets (flexible ducts) and zipper, Velcro, or steel ring (spiral ducts).

Does SULONG offer flame-retardant and anti-static ventilation ducts?

Yes. Both flexible and spiral ventilation ducts at SULONG are available with FR (flame retardant) or FRAS (flame retardant, anti-static) performance. Flame retardant standards include NFPA 701:2015 and DIN 4102 B2. The FRAS option is commonly specified for underground mining projects where hazardous gas dilution, anti-static safety airflow supply, and dust extraction are required under 24/7 continuous high-pressure ventilation operation.

How do I get a ventilation duct sample or request a quote?

To receive a sample, request a quotation, or obtain the full product catalog, contact SULONG directly. The contact person is Autumn Cui (tel +86-18251952515, email autumn@js-sulong.com, WhatsApp +86 182 5195 2515). The company address is No.9 Filter Material Industry Park, Funing, Yancheng, Jiangsu Province, China. You can download the SULONG Ventilation Duct Catalog here: Catalog of Ventilation Duct – SULONG.

Conclusion

Ventilation ducts are a critical safety component in underground mining and tunnel construction, and their specification demands attention to pressure ratings, material weight, flame retardancy, anti-static performance, and destination-market certifications. SULONG — Jiangsu Sulong Eco-Technologies Co., Ltd. — manufactures flexible and spiral ventilation ducts with in-house automated production, tensile strength up to 4,300 N, and international certifications including ISO 9001, ISO 14001, ISO 45001, EU ATEX, CE, and NFPA 701.

For procurement teams and engineers in the Awareness and Research stages, the practical next step is to verify the duct specification against your fan system and site safety requirements, then request a sample or catalog to evaluate fabric quality, seam construction, and end connections firsthand.