Safety-critical plastic fume extract ductwork: specification to operation

Martin Whiteley, Managing Director of Roperhurst, explains why plastic ductwork remains the material of choice for fume extract systems, and why design, fabrication and installation are vitally important considerations.

In modern construction and refurbishment projects, ductwork rarely grabs the headlines. It is often seen as a background system – a means to move air from one place to another.

Yet, when that ductwork is tasked with handling hazardous fumes, vapours, and process emissions, it becomes safety-critical. The design, fabrication, and installation of plastic fume extract ductwork is not only about system performance – it is about safeguarding operatives, protecting the environment, and ensuring compliance with increasingly stringent UK and international standards.

At Roperhurst, we have spent more than four decades manufacturing and installing thermoplastic ductwork systems for laboratories, hospitals, research facilities, and industrial plants across the UK. It’s offers designers, installers and end-users many advantages, but when applying these systems, safety, emissions control, and sustainability must guide every stage.

The case for thermoplastic ductwork

For aggressive and corrosive fume extraction applications, mild steel and even coated steel systems often fall short. Corrosion, contamination, and costly maintenance are common challenges.

For these reasons, plastic fume extract ductwork has become standard in laboratories, semiconductor facilities, pharmaceutical production, waste treatment plants, and educational settings where hazardous chemicals are in daily use.

Designing out risk

The priority in any safety-critical installation must be the protection of operatives. This begins with design decisions and continues through fabrication, installation, and maintenance.

1. Safe design Standards
   • Systems must comply with DW154 for plastic ductwork and BS EN 14175 for fume cupboards, with additional project-specific requirements often dictated by COSHH regulations.
   • Pressure and velocity ratings must be correctly matched to fan performance, ensuring that fumes cannot stagnate or leak at joints.
2. Fabrication and welding
   • Butt fusion, extrusion welding, and hot gas welding must be carried out by trained personnel, with welds inspected and spark tested where necessary.
   • Operative training and certification are key –  the integrity of a single weld can determine system safety.
3. Installation and access
   • Site teams must be appropriately supervised and provided with all necessary specialist tools and equipment, working to clear risk and method statements.
   • Because plastics are lighter, they reduce manual handling risks compared to steel, but safe working practices are still essential.
4. Ongoing maintenance and testing
   • Periodic quantitative and qualitative testing of extraction systems, coupled with visual inspection of duct joints and supports, ensures continued safety in operation.
   • Maintenance access must be designed in, with consideration given to safe cleaning and eventual decommissioning.

In short, operative safety depends on a culture of competence – from the workshop to the rooftop.

Environmental standards

Environmental responsibility is now a central pillar of building services design. For fume extract ductwork, this has three dimensions:

1. Controlled emissions
   • Hazardous substances must be captured and conveyed efficiently to treatment systems such as scrubbers, filters, or thermal oxidisers.
   • Leakage is unacceptable: not only does it endanger building occupants, there is a risk to the broader environment.
2. Materials and lifecycle
   • Thermoplastics are recyclable, and offcuts can be diverted from landfill where recycling streams are available.
   • By resisting corrosion, plastic ductwork reduces replacement frequency, lowering whole-life environmental impact.
3. Energy efficiency
   • Smooth bore plastics minimise pressure drop, reducing fan energy demand.
   • Correct sizing and careful layout design prevent over-specification and unnecessary energy consumption.

Clients and contractors alike recognise that sustainable design is not optional.

Emissions control

Laboratory and industrial processes can release a wide spectrum of contaminants: acid vapours, volatile organic compounds, particulates, or biohazards. Effective emissions control requires a systems approach of four Cs:

• Capture – local exhaust ventilation (LEV) systems must be designed to capture contaminants at source.
• Contain – ductwork must be sealed, resistant to attack, and pressure-rated to prevent fugitive emissions.
• Convey – airflow rates must ensure that hazardous fumes are transported safely to treatment.
• Control – treatment systems, such as packed-bed scrubbers or activated carbon filters, must be correctly sized and monitored.

Plastic ductwork is a vital part of this chain. Its chemical resistance means it can carry even the harshest emissions to abatement systems without degradation.

Importantly, correct welding and testing practices are essential to ensure containment integrity over the system’s life.

Best practice for UK projects

Based on our experience across many installations and 50 years of trading, the following best practice measures should guide contractors, architects, and consultants:

• Early engagement – involve ductwork specialists at design stage. Retrofitting safety measures later is costly and disruptive.
• Competency and training – only competent welders working with a competent employer should fabricate or install fume extract plastic ductwork.
• Testing and certification – specify spark testing, pressure testing, and inspection regimes to verify airtight performance.

The safety-critical backbone

Plastic fume extract ductwork may be unseen, running behind ceilings or across rooftops, but it is the silent guardian of safety and compliance in many of our most sensitive facilities.

As environmental standards tighten and safety expectations rise, the case for robust, expertly installed plastic fume extract ductwork has never been stronger. At Roperhurst, we see our role not just as a manufacturer and installer, but as a partner in building safer, cleaner, and more sustainable facilities across the UK.