Local Exhaust Ventilation (LEV) Systems

Fine particles and fumes from welding, grinding, cutting and chemical handling can cause respiratory irritation, occupational asthma, metal fume fever, silicosis and long-term lung damage. Solvent vapours can affect the nervous system and liver. An LEV system keeps these contaminants out of the worker's breathing zone, reducing exposure far more reliably than masks alone. Personal protective equipment then becomes a backup, not the only line of defence.

The closer the capture point is to the source, the less air you need to move and the better the protection. Source capture ventilation removes contaminants within centimetres of where they are generated, so they never have a chance to mix with room air. This is why LEV is ranked above general ventilation in the hierarchy of engineering controls.

Indian factory law requires employers to remove dust and fumes at the point of origin where they are likely to be injurious. Pollution control boards also regulate what leaves your stack. A properly designed, tested and documented LEV system helps you meet factory inspection requirements, audit checklists from global clients, and consent conditions for air emissions.

Dust that escapes a process settles on machines, electrical panels, finished goods and other batches. In pharma, food and electronics plants, this means cross-contamination and rejected product. LEV keeps the shop floor, equipment and products cleaner, reduces housekeeping time and protects sensitive machinery from abrasive or conductive dust.

The LEV hood is the most important part of the system. Its shape, size and position decide how much contaminant is captured and how much airflow is needed. We design each fume extraction hood and dust extraction hood around the actual process, the direction of contaminant release and the way operators work.

The extraction duct system is fabricated in GI, MS, stainless steel, PP or FRP depending on the contaminant. Blast gates and balancing dampers let each branch draw its design airflow, and allow unused hoods to be closed off to save energy.

The LEV air cleaner removes dust, fume, mist or vapour before discharge. Options include pulse-jet bag filters, cartridge dust collectors, cyclones, wet scrubbers, activated carbon filters, electrostatic precipitators, oil mist collectors and HEPA filters.

The LEV centrifugal fan provides the suction for the whole system. Fan type, blade design, material and motor rating are chosen for the required airflow, static pressure and the nature of the air being handled, including flameproof or ATEX extraction fans for hazardous areas.

The LEV discharge stack releases cleaned air at a safe height and velocity. It includes sampling ports for emission monitoring and, where needed, a weather cap design that does not deflect exhaust back down towards the roof.

An LEV airflow indicator at each hood and an LEV pressure gauge across each filter show operators, at a glance, whether the system is working. Differential pressure gauges also tell maintenance teams when filters need cleaning or replacement.

An enclosing hood surrounds the process fully or partially, so the contaminant is contained inside. Spray booths, laboratory fume hoods, powder dispensing booths and glove boxes are all enclosing hoods. They offer the best protection with the lowest airflow and are the first choice wherever the process allows.

A capturing hood sits outside the source and creates enough air velocity to pull contaminants in. Slot hood ventilation along tank edges, flanged hoods at workbenches and rectangular hoods at machines fall into this category. Adding a flange can reduce the airflow needed for the same capture by roughly 25%.

A receiving hood uses the natural movement of the contaminant. Canopy hoods catch rising hot fumes from furnaces and melting pots, while grinding wheel guards receive the particles thrown off the wheel. They only work when the contaminant actually travels towards the hood.

A fume extraction arm is a flexible, self-supporting arm with a capture hood that operators position close to the work. It is widely used for welding fume extraction, soldering and laboratory work, where the source position changes from job to job.

Downdraft extraction tables pull air down through a perforated or grilled worktop, drawing fumes and dust away from the operator's face. Backdraft extraction tables pull air horizontally from the rear. Both suit grinding, sanding, welding of small parts and plasma cutting.

On-tool extraction uses a small shroud built into a hand tool, such as a grinder, sander or saw, connected to a high-vacuum extraction unit. Because capture happens millimetres from the source, very little airflow is needed.

A centralised LEV system connects multiple hoods to a common duct network, air cleaner and fan. It suits production lines and workshops with many fixed extraction points, offering lower running costs per point, a single maintenance location and outdoor discharge.

Portable fume extractors combine a small fan, filter and extraction arm on a mobile unit. They are ideal for maintenance work, occasional welding and sites where installing ductwork is not practical. Most recirculate filtered air, so they must be matched carefully to the contaminant.

A local exhaust ventilation system for welding captures fine metal fume from MIG, TIG, stick and flux-cored welding using extraction arms, hoods, fume guns or welding tables. Welding fume is very fine, so these systems use cartridge filters with pulse cleaning and, where needed, spark arrestors.

Industrial dust extraction systems serve grinding, cutting, powder handling, sanding, bagging and conveying. They combine LEV hoods and ducting with a pulse-jet bag filter, cartridge dust collector or cyclone to capture dust and return it for disposal or reuse.

Chemical vapor extraction systems handle acid fumes, alkali mists and solvent vapours from reactors, tanks, charging points and plating lines. They use corrosion-resistant PP or FRP ducting and fans, and a wet scrubber or activated carbon unit to treat the exhaust.

Laboratory fume hood exhaust systems connect each fume cupboard to dedicated exhaust fans with the right face velocity, often with variable air volume control. We design the ducting, fans, scrubbers and stacks for R&D, QC and teaching labs.

Paint fume extraction systems combine spray booths, paint booth exhaust fans, dry filters or water-wash sections and stacks. They control overspray and solvent vapour, protect painters and improve finish quality.

Pharmaceutical LEV systems include downflow dispensing booths, sampling booths and point extraction at granulators, blenders and compression machines. They protect operators from potent APIs and prevent cross-contamination between batches, with HEPA filtration at the exhaust.

A baghouse dust collector uses fabric filter bags cleaned automatically by compressed-air pulses. It handles high dust loads and large airflows, making it the workhorse for cement, powder, foundry, grinding and bulk-handling applications. Bag material is chosen for temperature, moisture and chemical resistance.

A cartridge dust collector packs a large pleated filter area into a compact housing. It is ideal for fine, dry particles such as welding fume, laser and plasma cutting fume, and light powders, with high efficiency and easy filter changes.

Cyclones use centrifugal force to separate coarse and heavy particles. They have no filters to replace and are often used as a pre-separator before a bag filter, reducing load on the filters and recovering reusable material such as metal chips or wood dust.

An LEV scrubber system washes contaminated air with water or a chemical solution. Packed-bed and venturi scrubbers remove acid fumes, alkali mists, soluble gases and sticky or hot dust. Built in PP or FRP, they are standard for chemical, pharma, plating and pickling processes.

Activated carbon fume extraction adsorbs organic solvent vapours and odours. It suits low-concentration VOC applications such as small paint areas, laboratories, printing and adhesive work. Carbon life depends on the load, so we size the bed for realistic change intervals.

Oil mist extraction systems capture coolant and oil mist from CNC machines, grinding and forging using coalescing filters or electrostatic precipitators. These systems recover oil, keep machines and floors clean, and prevent slippery, contaminated work areas.

An LEV HEPA filter provides final-stage filtration for toxic, potent or carcinogenic dust, including APIs, silica and heavy metals. HEPA stages are often installed in safe-change housings so maintenance staff are not exposed when filters are replaced.

The ACGIH Industrial Ventilation manual is the most widely used engineering reference for LEV system design. It provides recommended capture velocities, hood design data, duct transport velocities and calculation methods for airflow and static pressure. Our LEV airflow calculation and duct sizing follow these methods.

ANSI/AIHA Z9.2 sets out the fundamentals for design, construction, operation and testing of local exhaust ventilation systems. It emphasises documented design criteria, commissioning, baseline performance records and periodic testing, practices we build into every project handover.

HSE local exhaust ventilation guidance, HSG258, is a practical reference on hood selection, commissioning, user manuals, log books and thorough examination and testing, typically at least every 14 months. Many multinational plants in India follow it as best practice, alongside OSHA and DOSH local exhaust ventilation guidance used by global groups.

The Factories Act, 1948 requires effective measures to prevent the inhalation and accumulation of injurious dust and fumes, including exhaust appliances placed as near as possible to the point of origin. Provisions on ventilation and dangerous fumes are carried forward under the Occupational Safety, Health and Working Conditions Code, 2020 and applicable state rules, including the Maharashtra Factories Rules. Our documentation supports inspections under these requirements.

The Central and State Pollution Control Boards, including MPCB in Maharashtra, set limits on particulate and gaseous emissions and stack height through consent conditions. We select air cleaners to meet your consent limits and provide stacks with sampling ports and platforms for third-party emission monitoring.

We start by studying the process: what is released, in what form, how fast, how hot and for how long. We note particle size, toxicity, flammability, moisture, corrosiveness and operator movements. This assessment drives every design decision that follows.

We choose the hood type that gives the best control with the least airflow, preferring enclosures, then receiving hoods, then capturing hoods. Placement accounts for operator access, material handling, cross-draughts from doors and fans, and the direction the contaminant travels.

LEV capture velocity is the air speed needed at the source to draw the contaminant into the hood. Face velocity is the air speed across an enclosure opening, such as a booth or fume hood. Typical design ranges, based on ACGIH guidance:

For a simple plain hood, the LEV capture velocity calculation uses the relationship below, where Q is airflow, V is capture velocity, X is the distance from the hood face and A is the hood face area. A flanged hood needs about 75% of this airflow.

Q = V \left(10X^{2} + A\right)

The key takeaway: capture velocity falls very quickly with distance. Doubling the distance from hood to source can need around four times the airflow, which is why hood position matters so much.

LEV conveying velocity must keep particles airborne all the way to the collector. Too low and dust settles and blocks ducts; too high and energy use, noise and abrasion rise.

LEV duct sizing sets each branch diameter to achieve the target duct velocity at its design airflow. Branches are balanced by design, using calculated duct sizes, or with balancing dampers, so every hood receives its share of air. We favour gradual transitions, long-radius bends and branch entries at 30 to 45 degrees.

LEV static pressure calculation adds up losses from hood entry, ducts, bends, branches, the air cleaner and the stack. LEV fan sizing then matches airflow and total pressure to a fan curve with margin for filter loading. We choose backward-curved, radial or paddle-blade centrifugal fans based on the dust load, and specify motors and VFDs for efficient operation.

The air cleaner is chosen for the contaminant type, concentration, particle size, temperature, moisture, explosibility and the emission limit you must meet. For some processes, two stages, such as a cyclone plus bag filter, or a scrubber plus mist eliminator, give the best result.

The stack must release air high enough, and fast enough, to clear the roof and nearby buildings. We typically design for a discharge velocity of around 15 m/s or more, avoid rain caps that deflect exhaust downwards, and keep stacks away from fresh air intakes. Stack height also follows pollution control board requirements.

Every cubic metre extracted must be replaced. Without make-up air, the building runs under negative pressure, hood performance drops, doors slam and fumes back-draft from other sources. We design LEV make up air through louvres, fresh air units or tempered air systems, located so incoming air does not disturb capture at the hoods.

Many dusts, including pharma powders, flour, sugar, wood, aluminium and plastics, are combustible. For these applications we provide explosion vent panels, flameless venting for indoor collectors, isolation valves and rotary airlocks to stop a flame travelling back through the ductwork to the workplace.

Where flammable vapours or combustible dusts are present, we specify explosion proof LEV equipment: flameproof motors, spark-resistant fan construction and ATEX extraction fans suited to the hazardous area classification of your plant.

Grinding, cutting and welding throw hot sparks that can ignite filter media. Spark arrestors and drop-out boxes upstream of the dust collector cool and trap sparks before they reach the filters, a simple addition that prevents costly filter fires.

Acid fumes and corrosive vapours destroy mild steel ducts quickly. We fabricate hoods, ducts, fans and scrubbers in stainless steel, polypropylene or FRP to suit the chemistry, temperature and fire rating needed for the application.

Where ducts pass through fire-rated walls, we provide fire dampers where they are appropriate for the exhaust stream, along with temperature sensors, sprinkler or suppression connections in collectors, and fire-alarm interlocks that shut down fans safely.

LEV VFD control lets the fan run at the speed actually needed. Because fan power drops sharply with speed, even a modest speed reduction gives large energy savings. VFDs also allow soft starting and constant-pressure control as filters load.

Motorised dampers open only at workstations in use, triggered by sensors, switches or machine signals. The fan then slows down to match the active hoods, so you only pay for the extraction you need.

Interlocks prevent a machine from starting unless its extraction is running, and can keep the fan running for a set time after work stops to clear residual fume. This removes reliance on operators remembering to switch on extraction.

LEV differential pressure monitoring across filters triggers pulse cleaning only when needed, saves compressed air, and alerts maintenance teams before filter loading starts to reduce hood airflow.

An LEV monitoring system with PLC control can log airflow, pressure, fan status and alarms, and connect to your SCADA or building management system. LEV BMS integration gives your facility team real-time visibility and a digital record for audits.

LEV keeps dust, fumes and vapours out of the breathing zone, reducing occupational illness, absenteeism and dependence on respirators. A healthier workforce is a more productive one.

By capturing at the source, LEV stops contamination spreading to neighbouring work areas, offices and stores, protecting people who are not even working on the process.

Because LEV only handles concentrated air near the source, it needs far less airflow than diluting a whole building, which means smaller fans, less make-up air and lower cooling or heating loads.

A well-documented local exhaust ventilation LEV system supports compliance with factory rules, pollution control consent conditions and client audit requirements.

In pharma and food manufacturing, LEV at dispensing, sampling, blending and packing points prevents powders from migrating between rooms and batches, supporting GMP compliance.

Many dust collectors return clean, dry material that can be reused or sold, such as metal powder, pharma ingredients, food powders and wood dust, offsetting part of the running cost.

Less dust settling on machines, electrical panels and floors means lower cleaning effort, fewer breakdowns and a more professional plant for client visits.

There is no universal LEV system. A hood that works well for one process can fail on another. Each system must be engineered for the specific contaminant, process and layout.

A fume extraction arm left 60 cm away from the weld provides little protection. Operator training, sensible hood design and airflow indicators are essential to make LEV work in daily practice.

Filters load, ducts clog, belts wear and dampers get moved. Without regular inspection, performance can drop without anyone noticing. Scheduled testing and maintenance are part of owning an LEV system.

Extraction fans and the conditioning of make-up air consume energy. Good design, VFDs and on-demand controls keep this under control.

Fans, pulse-jet cleaning and high duct velocities generate noise. We address this with correct fan selection, acoustic enclosures, silencers and outdoor fan placement where possible.

LEV for welding uses extraction arms, fume hoods, welding tables and centralised cartridge collectors to control MIG, TIG and arc welding fume. We also design LEV for cutting, including plasma and laser cutting tables with downdraft extraction.

Pharmaceutical LEV systems serve dispensing, sampling, granulation, blending, compression, coating and packing, with HEPA filtration, SS construction and containment to protect operators and product.

Chemical industry LEV captures vapours and fumes at reactor manholes, charging points, drum filling, centrifuges and storage tanks, treated through scrubbers or carbon units.

We design fume hood exhaust, snorkel extraction and scrubber systems for QC, R&D and academic laboratories, balancing safety with energy use.

Spray booths, paint booth exhaust fans and overspray filtration for industrial, automotive and furniture finishing, including solvent vapour control.

LEV for grinding uses receiving hoods, wheel guards, backdraft benches and dust collectors to capture metal dust, abrasive particles and buffing lint.

Woodworking LEV connects saws, planers, routers and sanders to dust collectors with explosion protection, keeping fine wood dust out of the air.

Canopy hoods over furnaces, extraction at shake-out, fettling and sand plants, and high-temperature ducting and bag filters for foundry fumes and dust.

Dust extraction at flour, sugar, spice and powder handling points, plus oil mist and steam extraction, with hygienic design and material recovery.

Compact extraction arms and bench-level fume extractors for soldering, PCB assembly and rework stations, with filtration for flux fumes.

Local and general exhaust for battery charging rooms to remove hydrogen and acid mist, with flameproof exhaust fans and appropriate air change rates.

Extraction for moulding, extrusion, mixing, compounding and printing presses to control fumes, VOCs, carbon black and ink solvents. We also handle automotive LEV systems and vehicle exhaust extraction for service workshops and test bays.

A Swedish manufacturer known for fume extraction arms, welding fume extraction, vehicle exhaust extraction and industrial dust collection systems.

A global filtration company whose industrial dust collectors, including cartridge and bag-type units, are widely used for dust and fume collection.

A Swedish air filtration specialist offering HEPA and HVAC filters, along with cartridge dust collectors for industrial applications.

A German company specialising in welding fume extraction, including mobile fume extractors, extraction arms and central filtration systems.

A Dutch manufacturer of welding fume extraction, extraction arms, filtration units and vehicle exhaust extraction systems.

An Indian engineering company with offerings in energy and environment, including air pollution control equipment such as bag filters, scrubbers and electrostatic precipitators.

Several reputable Indian and international manufacturers supply centrifugal fans, extraction arms, cartridge collectors, scrubbers and filters. We evaluate equipment on performance data, spare availability, service support and total cost of ownership, and recommend what fits your process and budget best.

We monitor filter differential pressure, check solenoid valves, diaphragms, timers and compressed air supply, and replace bags or cartridges before they restrict airflow.

We check hoppers, rotary valves and dust bins, and help set emptying routines so collected dust never backs up into the filters.

Ducts are inspected through cleanout doors for build-up, and joints, flexible connectors and access doors are checked for leaks that reduce suction at the hoods.

We inspect impellers for wear and build-up, check belt tension and alignment, lubricate bearings, measure vibration and motor current, and confirm fan speed matches commissioning values.

For scrubbers, we check pump performance, spray nozzles, packing condition, water level, blowdown, pH and chemical dosing, keeping removal efficiency within design limits.

We inspect hoods for damage and modifications, check extraction arm joints, hoses and friction settings, and verify airflow indicators are working and visible to operators.

Problem: Fumes or dust visibly escape the hood. Solution: Move the hood closer, add flanges or side baffles, convert to a partial enclosure, and shield the source from cross-draughts caused by doors, pedestal fans or make-up air.

Problem: Booths or fume hoods fall below design face velocity. Solution: Check for blocked filters, closed dampers, slipping belts or duct leaks, then rebalance the system or increase fan capacity if the design was undersized.

Problem: Ducts fill with dust and suction drops at the far hoods. Solution: Resize ducts to achieve the correct conveying velocity, remove flat horizontal runs where possible, and add cleanout doors for inspection.

Problem: The filter gauge reads high and airflow falls. Solution: Check pulse cleaning and compressed air quality, empty hoppers, replace blinded filters, and review the air-to-cloth ratio if filters load too quickly.

Problem: Noisy, vibrating fans with worn impellers. Solution: Clean or replace the impeller, balance the rotor, check bearings and alignment, and if the fan handles dusty air, relocate it downstream of the collector.

Problem: Air enters through damaged joints and open doors, reducing suction at hoods. Solution: Seal joints, replace damaged flexible connectors and gaskets, and close unused openings.

Problem: Combustible dust or sparks in an unprotected system. Solution: Add spark arrestors, explosion vents, isolation valves, temperature monitoring and correct earthing of ducts and filters.

Problem: Exhaust is drawn back in through air intakes or windows. Solution: Raise the stack, increase discharge velocity, replace deflecting rain caps and relocate intakes away from the exhaust plume.

We replace poorly performing hoods with enclosures, flanged or slot hoods, or extraction arms designed for the actual process, often improving capture while reducing airflow.

If your system discharges untreated air, we add dust collectors, scrubbers or carbon filters to meet pollution control board limits and consent conditions.

Retrofitting VFDs, automatic dampers and machine interlocks turns a fixed-speed system into an energy efficient LEV system with a short payback period.

We replace corroded ducts, worn impellers and inefficient fans with correctly sized, corrosion-resistant equipment.

For systems handling combustible dust, we add explosion venting, isolation, spark detection and ATEX-rated components to bring the installation up to a safer standard.

The air cleaner is often the largest single cost item. Cartridge collectors, pulse-jet bag filters, cyclones and PP/FRP wet scrubbers vary widely in price depending on airflow, filter area, material of construction, explosion protection and automation level.

Duct cost depends on diameter, length, material (GI, MS, SS, PP or FRP), number of fittings and installation height. Fan cost depends on airflow, static pressure, construction and motor type, including flameproof motors. Stack cost depends on height, material and access platforms.

• Type and toxicity of contaminant
• Number, type and spread of extraction points
• Required airflow and static pressure
• Air cleaner type and emission limits
• Material of construction (GI, SS, PP, FRP)
• Explosion protection and hazardous-area requirements
• Controls, VFDs, monitoring and BMS integration
• Make-up air requirements
• Site access, working height and shutdown constraints
• Testing, documentation and AMC scope

The lowest price is rarely the lowest cost. An undersized fan or poorly designed hood can make the whole investment ineffective. Share your process details with us for an accurate, itemised LEV quotation.