Understanding the Equipment
Chemical fume containment is a fundamental requirement in any laboratory that handles volatile, toxic, or reactive substances. A Ducted Fume Hood — also referred to as a ducted fume cupboard or ducted fume cabinet — is the primary engineering control for this purpose: a ventilated enclosure that draws contaminated air away from the operator and exhausts it to the external atmosphere through a dedicated fume duct and exhaust system.
Unlike recirculatory or ductless units that filter exhaust air through activated carbon and return it to the room, a fume hood with a duct routes the entire contaminated air volume out of the building. This makes the ducted configuration the appropriate choice for any procedure involving substances that cannot be adequately captured by filter media — including perchloric acid, concentrated mineral acids, aldehydes, mercury, and volatile organic compounds at high concentrations. Where the chemical inventory includes substances incompatible with carbon filtration or where regulatory requirements mandate external exhaust, the ducted approach is the only compliant option.
The Advalab ADDFH-512 is a laboratory-grade ducted fume hood developed for research, hospital, and industrial laboratory environments where face velocity consistency, airflow uniformity, and material compatibility with the chemical inventory are non-negotiable specification requirements. Laboratories comparing configurations across the product range can review the full selection on the Advalab ducted fume hood models page.
Fume Hood Unit (ADDFH-512)
Baffled exhaust plenum draws air uniformly across work surface
Negative pressure within the hood prevents chemical vapours from escaping into the laboratory environment
Technical Principle
The containment performance of any ducted fume cupboard is fundamentally determined by the inward face velocity — the average speed at which room air is drawn through the sash opening into the hood interior. Face velocity is expressed in metres per second (m/s) or feet per minute (fpm) and is the single most critical performance parameter for evaluating whether a fume hood unit provides adequate operator protection for a given chemical hazard level.
ADDFH-512 rated face velocity: 0.4–0.6 m/s (adjustable via VAV damper). Verify applicable regulatory requirements for your jurisdiction.
Face velocity must be understood in conjunction with airflow uniformity. A hood that achieves its target average face velocity but delivers that airflow unevenly — with stagnant zones near corners or high-velocity jets at the sash centre — can still allow vapour escape at low-velocity points. The ADDFH-512 employs a multi-baffle rear plenum design that redistributes exhaust suction across the full width and height of the hood interior, minimising velocity variation across the sash face to within ±20% of the mean value — in conformance with EN 14175-3 uniformity requirements.
Sash position directly affects face velocity. As the sash is raised, the opening area increases and — if the exhaust volume flow is fixed — face velocity decreases proportionally. The ADDFH-512 incorporates a variable air volume (VAV) control damper with a sash position sensor that automatically adjusts exhaust volume to maintain the target face velocity at any sash height between closed and the maximum working opening. This prevents the excessive air consumption that occurs when a constant-volume hood is used with a partially raised sash, while maintaining containment across the full sash travel range.
The fume cupboard extract ductwork connecting the hood to the building exhaust system is a critical system component that is frequently underspecified. Duct diameter, run length, number of bends, and duct material all affect the static pressure at the hood collar, which in turn affects the effective exhaust flow delivered by the fan. The ADDFH-512 product documentation includes a duct pressure drop calculation guide to assist mechanical engineers in sizing the fume cupboard ductwork correctly for the installed location.
Laboratory Applications
Procedures involving concentrated mineral acids — hydrochloric, sulphuric, nitric, perchloric — and strong bases generate corrosive vapours that exceed the capacity of activated carbon filtration. A ducted fume hood exhausts these vapours directly to the atmosphere via the fume duct, preventing reagent breakthrough into the laboratory air supply. Perchloric acid work additionally requires a wash-down hood with non-sparking interior surfaces and a dedicated exhaust duct with periodic water-flush capability to prevent perchlorate crystallisation in the duct run.
Rotary evaporation, solvent transfers, and open-vessel heating of organic solvents generate vapour concentrations that must be contained and exhausted away from ignition sources and personnel. A ducted fume hood benchtop configuration provides the ventilated enclosure for these procedures, with earthed worktop surfaces and spark-resistant interior components suitable for flammable solvent work in accordance with laboratory safety regulations.
Pharmaceutical laboratories performing synthesis, formulation, and quality control work with potent or sensitising compounds require containment that prevents operator exposure below occupational exposure limits. The ducted configuration, with its continuous external exhaust, provides the air change rate and containment performance needed for scheduled substances, highly active pharmaceutical ingredients (HAPIs), and compounds with low occupational exposure limits.
Industrial fume hood installations in manufacturing quality laboratories, metal analysis facilities, and surface treatment laboratories handle sample digestion with strong acids, mercury cold vapour generation, and acid dissolution of alloy samples. These high-vapour-burden procedures require robust fume duct exhaust capacity and hood interior materials — typically polypropylene or fibreglass-reinforced polyester — with rated chemical resistance to concentrated mineral acids.
University and college teaching laboratories conduct a broad range of undergraduate experiments — organic synthesis, titrations, reflux reactions — with variable and sometimes unpredictable chemical combinations. A ducted fume cupboard with a full-width sash, clearly visible face velocity indicator, and audible alarm on low-flow or sash-open conditions provides the containment performance and user feedback appropriate for an educational environment with rotating, variable-experience operators.
Hospital clinical laboratories and pathology departments use fume hoods for fixative preparation (formaldehyde, glutaraldehyde), staining procedures, solvent-based histology reagent handling, and acid preparation for trace metal analysis. The ducted configuration ensures that formaldehyde — a known carcinogen subject to strict occupational exposure limits — is contained and exhausted without recirculation into the laboratory environment, regardless of procedure duration or frequency.
Installation Considerations
The performance of a Ducted Fume Hood is only as good as the exhaust system connected to it. Fume cupboard ductwork that is undersized, excessively long, or poorly routed creates back-pressure at the hood collar that reduces actual exhaust flow below the design value — effectively lowering face velocity without any visible indication at the hood itself unless a face velocity monitor is installed.
Key Ductwork Design Parameters — ADDFH-512 Installation
Duct Diameter and Velocity
Duct transport velocity must remain above 7–10 m/s to prevent vapour condensation and particulate settling in horizontal runs. Duct diameter is calculated from exhaust volume flow (m³/h) and target transport velocity. Under-sizing the duct to reduce installation cost is the most common cause of hood underperformance after commissioning.
Duct Material Selection
Standard galvanised steel ductwork is suitable for general VOC and mild acid vapours. Polypropylene or PVC duct is required for concentrated mineral acid exhaust. Stainless steel is specified for oxidising acids and perchloric acid applications. Duct joints must be sealed with chemically compatible mastic; flanged rather than slip connections are preferred for acid service.
Bends, Fittings, and Static Pressure
Each 90° elbow adds equivalent resistance of approximately 1.5 duct diameters to the effective run length. Total static pressure at the fan must account for all fittings, the hood collar resistance, and the stack discharge loss. A poorly routed fume duct run with multiple elbows can increase fan static pressure requirement by 40–60% relative to a straight run — requiring a larger fan or resulting in lower actual exhaust flow.
Exhaust Stack Height and Discharge
The exhaust stack must discharge above the roofline at sufficient height and velocity to prevent re-entrainment into building air intakes or adjacent windows. Minimum stack height and discharge velocity are determined by local building and safety regulations and are influenced by prevailing wind patterns, adjacent structure heights, and the toxicity of the exhausted chemicals.
Make-up air is an equally critical installation consideration. A ducted fume hood exhausts a significant air volume — typically 800–2,000 m³/h, depending on hood width and face velocity — that must be replaced by conditioned supply air to the laboratory. Insufficient make-up air supply causes the laboratory to go negative relative to adjacent spaces, drawing unconditioned air through gaps and doors, which disturbs the hood's airflow pattern and can cause containment failure. The ADDFH-512 installation guide specifies minimum supply air flow rates for each hood width configuration.
Procurement Guidance
A wider hood requires proportionally greater exhaust air volume to maintain the target face velocity. In laboratories with constrained HVAC capacity, specifying the widest available hood may exceed the building's exhaust capacity and result in either under-ventilating the hood or starving adjacent supply-air systems. Always confirm the exhaust volume requirement against the HVAC system's design capacity before finalising hood width.
Standard epoxy resin worktops and painted steel interiors are adequate for general organic chemistry but degrade rapidly on exposure to concentrated acids, bleach, or strong oxidising agents. Polypropylene-lined interiors are appropriate for acid-heavy applications; ceramic or marine-grade epoxy worktops are required for perchloric acid and strongly oxidising environments. Chemical incompatibility between the hood interior and the reagent inventory causes premature liner failure, creates secondary contamination, and requires disruptive hood removal and refurbishment.
A ducted fume hood that has been installed but not commissioned — with a measured face velocity survey at multiple sash positions — may be operating at a face velocity significantly different from the design value. Face velocity commissioning using a calibrated anemometer at a minimum of six measurement points across the sash face, documented to EN 14175-4 or equivalent, is the only way to confirm that the hood provides the containment performance it was specified to deliver. Annual re-commissioning verifications are required under most laboratory safety frameworks.
Vertical-rise sashes, horizontal-sliding sashes, and combination sash designs each offer different ergonomic and containment trade-offs. Vertical sashes provide a full-width working opening but require adequate overhead clearance and generate the highest exhaust volume when fully open. Horizontal sashes limit the working aperture width but maintain a fixed maximum opening height, reducing exhaust volume variation. Selecting a sash type based on availability rather than the physical requirements of the planned work — tall apparatus versus wide sample arrays — leads to ergonomic conflicts that operators work around by compromising containment.
Adding a ducted fume hood to an existing laboratory without updating the supply air system creates a net exhaust imbalance that depressurises the room. Cross-draughts from door gaps, supply diffusers placed directly in front of the hood sash, or high-velocity supply jets directed at the hood opening all destabilise the inward airflow pattern and reduce effective containment — even when the measured face velocity at the sash plane appears acceptable.
At full exhaust flow, a fume hood unit generates noise from the turbulent airflow at the sash face and from the duct system. In open-plan or shared laboratories where multiple hoods operate simultaneously, cumulative noise levels can compromise communication and concentration. Verify the hood's noise specification at rated exhaust flow against the relevant laboratory noise exposure standard for the working environment, particularly in settings where extended operator occupancy is anticipated.
Product Specifications
For the complete datasheet, interior configuration options, and ductwork specification guide, visit the ADDFH-512 product page.
| Parameter | Specification |
|---|---|
| Internal Width Options | 900 mm / 1,200 mm / 1,500 mm / 1,800 mm |
| Internal Depth | 750 mm (nominal working depth) |
| Internal Height (to baffle) | 750 mm |
| Face Velocity (target) | 0.4–0.6 m/s (VAV controlled; ±10% of set point) |
| Face Velocity Uniformity | ≤ ±20% deviation from mean across sash face |
| Exhaust Volume Flow | 900–2,200 m³/h (width and face velocity dependent) |
| Sash Configuration | Vertical-rise (standard); horizontal-sliding (optional) |
| Sash Glazing | 6 mm safety laminated glass (EN 12150) |
| Worktop Material | Chemical-resistant epoxy resin (standard); polypropylene (acid option) |
| Interior Liner | Painted steel (standard); polypropylene full-liner (acid option) |
| Exhaust Collar Diameter | 200 mm – 315 mm (width dependent; round spigot) |
| VAV Control | Motorised damper with sash position sensor; BMS signal output (0–10 V) |
| Airflow Monitor & Alarm | Digital face velocity display; audible and visual alarm on low-flow / sash-open |
| Services Provision | Cold water, hot water, gas, electrical (IEC 60309) — as specified |
| Containment Test | SF₆ tracer gas test to EN 14175-3; containment ≤ 0.1 ppm at sash face |
| Electrical Supply | AC 230 V / 110 V, 50/60 Hz (monitor unit and services) |
| Safety Standards | CE marked; compliant with COSHH containment requirements |
Comparative Analysis
The choice between a ducted fume cabinet and a ductless (recirculatory) unit must be driven by the chemical inventory and the facility's infrastructure constraints — not by installation convenience.
| Characteristic | Ducted Fume Hood (ADDFH-512) | Ductless / Recirculatory Hood (general category) |
|---|---|---|
| Exhaust Destination | External atmosphere — no recirculation to lab | Filtered air returned to laboratory room |
| Suitability for Mineral Acids | All concentrations — including perchloric, hydrofluoric | Carbon filters ineffective for most inorganic acids |
| Filter Replacement Requirement | None — no filter media required | Regular carbon filter replacement — interval varies by chemical load |
| Installation Requirements | Requires fume duct, exhaust fan, make-up air supply | Plug-in; no ductwork — flexible placement |
| Chemical Inventory Flexibility | Unrestricted — no filter compatibility constraints | Restricted to chemicals compatible with installed filter type |
| Regulatory Acceptance | Universally accepted for all chemical classes under COSHH and equivalent | Accepted for specific chemicals with validated filter; not for carcinogens or acutely toxic agents in most jurisdictions |
| Energy Consumption | Higher — continuous exhaust of conditioned air | Lower — recirculated air reduces HVAC load |
| Containment Test Standard | EN 14175-3 SF₆ tracer gas test — ≤0.1 ppm at sash face | Various — filter-based standards; containment test not universally mandated |
* Comparison reflects general category characteristics. Verify individual model specifications and applicable local safety regulations before procurement.
Product Category
The Advalab fume hood category covers ducted, ductless, perchloric acid, radioisotope, and walk-in fume hood configurations developed for research laboratories, hospital facilities, pharmaceutical production, and industrial laboratory environments. Each unit is specified according to the applicable EN 14175 series containment standards.
Visit the Advalab home page for the full laboratory furniture and safety equipment portfolio, including biosafety cabinets, laminar flow units, laboratory casework, and chemical storage systems.
External exhaust — unrestricted chemical compatibility.
Carbon-filtered recirculation—flexible placement, chemical-specific
Wash-down design, dedicated duct, non-sparking interior
Floor-mounted, full-access, tall apparatus and bulk chemical work
Frequently Asked Questions
Access the complete technical specifications, interior configuration options, and ductwork sizing guide for the Advalab ADDFH-512 Ducted Fume Hood.
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