Industrial Dust Control Glossary

A central dust extraction system is a fixed network of capture hoods, ductwork, a dust collector, a fan and controls that removes dust from several production points to one filtration unit. It suits permanent workstations with predictable duty cycles, such as composite sanding shops, woodworking lines and powder handling. Performance depends on hood design, duct transport velocity, network balance and filter condition, not on fan size alone. In Saudi Arabia, DusTech designs, supplies, installs and commissions CDES projects as prime contractor, including airflow verification at each capture point at handover.

A portable dust extraction unit is a self-contained machine with its own fan, filter and collection container, connected to the source by a flexible hose, an on-tool shroud or a small hood. It suits changing workstations, maintenance bays, pilot lines and intermittent tasks where a ducted network is impractical. Its effectiveness depends on the hose length, the hood position and the filter loading at the actual operating point. DusTech supplies and installs portable units in Saudi Arabia and helps teams define a repeatable set-up for each task.

Source capture, also called local exhaust ventilation, removes dust at the point where a process releases it, before it reaches the operator’s breathing zone or settles on the building. It uses hoods, enclosures, downdraft tables or on-tool shrouds connected to an extractor. Source capture is generally more effective than general room ventilation because it intercepts contaminants close to their origin. The hood must follow the direction and momentum of the dust and remain usable by operators. DusTech designs source-capture arrangements as the starting point of every extraction project.

Capture velocity is the air speed needed at the point of dust release to overcome the dust’s own momentum and surrounding air movement and draw it into a hood. It is not the same as the air speed inside the duct. The required value depends on how the process releases dust, from gentle pouring to high-speed grinding, and falls quickly as the hood moves away from the source. Engineers use capture velocity with hood geometry to calculate the airflow each point needs, which in turn sizes the ductwork and collector.

Duct transport velocity is the minimum air speed inside extraction ductwork that keeps collected dust suspended until it reaches the collector. If the velocity is too low, dust settles in the duct, reducing airflow and, for combustible materials, creating a fire or explosion hazard. If it is too high, energy use, noise and abrasive wear increase. Heavier, coarser or stickier materials need higher transport velocities. Duct diameters in a central system are chosen so every branch maintains a suitable transport velocity under the intended operating scenarios.

A dust collector is the unit in an extraction system that separates dust from the airstream and holds it for safe removal. Common types include cartridge collectors, baghouses, cyclones used as pre-separators, and wet collectors for specific applications. The collector is sized to the design airflow and the dust loading, and must allow safe filter changes and container emptying. Where dust is combustible, the collector is often the location of explosion venting or isolation measures. Selecting a collector is a process decision, not only a catalogue choice.

A cartridge filter is a pleated filter element, usually cylindrical, used in compact dust collectors. Pleating gives a large filter area in a small housing, which suits fine, dry dusts such as composite, metal grinding and powder fines. Cartridges are typically cleaned in place by reverse pulses of compressed air. They are less suited to very sticky, fibrous or high-temperature dusts, where bags may perform better. Media choice, pleat spacing and cleaning settings should match the actual dust, and filter changes should be planned with safe access and containment.

A baghouse is a dust collector that uses long fabric filter bags, supported on cages, to separate dust from the airstream. Bags are cleaned by pulse-jet, reverse air or shaking. Baghouses handle higher dust loads, coarser or fibrous materials and larger airflows than many cartridge collectors, and are common in cement, minerals, grain and wood processing. They need more space and headroom for bag removal. As with any collector, combustible-dust protection, safe emptying and access for inspection must be designed in from the start.

Class M and Class H are dust-class ratings for industrial vacuum cleaners and extractors, defined in IEC/EN 60335-2-69. Class M machines are intended for dusts of medium hazard, with a stated filtration performance and controlled emptying. Class H machines are intended for high-hazard dusts and have a higher filtration requirement across the whole machine. These classes describe filtration and dust-handling performance only. They do not indicate suitability for explosive atmospheres, which is covered separately by ATEX equipment marking. DusTech supplies units with the dust class matched to the material.

Combustible dust is any finely divided solid that can burn or explode when dispersed in air in sufficient concentration and ignited. Many everyday industrial materials qualify, including flour, sugar, grain, wood, many plastics, pharmaceuticals and metals such as aluminium and magnesium. Hazards arise both in process equipment and from settled layers on beams, ducts and lights that can be lifted into a secondary explosion. Control relies on a Dust Hazard Analysis, source capture, suitable equipment and regular housekeeping of elevated surfaces, which DusTech delivers with ATEX Zone 22 equipment.

Kst and Pmax are laboratory-measured explosion parameters for a specific dust. Pmax is the maximum explosion pressure the dust cloud produces in a closed vessel, in bar. Kst, the deflagration index in bar·m/s, describes how fast that pressure rises and is used to group dusts into explosion classes St 1, St 2 and St 3. Engineers use both values to size explosion vents, select isolation devices and confirm whether equipment can withstand an event. Values vary with particle size and moisture, so testing the actual material is often recommended.

ATEX Zones 20, 21 and 22 classify areas where an explosive atmosphere of combustible dust may occur. Zone 20 is where a dust cloud is present continuously or for long periods, typically inside equipment. Zone 21 is where a dust cloud is likely in normal operation. Zone 22 is where a dust cloud is not likely in normal operation and, if it occurs, persists only briefly, such as around housekeeping tasks. Area classification is set by a competent assessment of the site. DusTech’s high-reach cleaning and rental vacuums are Zone 22 rated equipment.

Equipment category II 3D is an ATEX marking for surface-industry equipment (Group II) that provides a normal level of protection (category 3) in dust atmospheres (D). It is the category intended for use in Zone 22. Category 2D equipment is suitable for Zone 21 and 22, and category 1D for Zones 20, 21 and 22. The full marking also states the dust group, such as IIIB or IIIC, and a maximum surface temperature. Checking the complete marking against the site classification and material is essential before mobilising any ATEX equipment.

Dust groups IIIB and IIIC divide combustible dusts by electrical behaviour. Group IIIB covers non-conductive combustible dusts, such as flour, sugar, wood and most plastics. Group IIIC covers conductive dusts, typically metals such as aluminium, which can bridge electrical gaps and therefore need a higher level of protection. Equipment marked IIIC is also suitable for IIIB, but not the reverse. Selecting a vacuum or extractor for metal dust without confirming IIIC suitability is a common error. DusTech confirms the dust group before supplying or renting ATEX equipment.

Explosion venting is a protective measure that releases the pressure of a dust explosion through a weak panel or vent of calculated size, so that a collector, silo or vessel is not destroyed. The vent area is sized from the dust’s Kst and Pmax, the vessel volume and its strength. Vented flame and pressure must discharge to a safe area, which often decides where a collector can be located. Where safe discharge is impossible indoors, flameless venting devices may be used. Venting does not stop an explosion from travelling back through ductwork; isolation does.

Explosion isolation prevents a dust explosion in one part of a system, typically the collector, from propagating through connected ductwork to workstations, other vessels or occupied areas. Passive devices include flap valves that close under the pressure wave; active systems use sensors to trigger fast-acting valves or chemical barriers. Rotary valves can provide isolation on the dust discharge. The need for isolation is identified in the Dust Hazard Analysis and is specified together with venting or suppression. Removing isolation to save cost leaves operators exposed at the hood.

NFPA 652 is the US National Fire Protection Association standard on the fundamentals of combustible dust, which requires owners to determine whether their dusts are combustible, carry out a Dust Hazard Analysis and manage the hazards. NFPA 660 is the newer consolidated standard that brings NFPA 652 and the industry-specific combustible-dust standards into one document. Both are widely referenced in Saudi industrial projects as good engineering practice. DusTech designs systems and housekeeping methods in accordance with these principles; they are design references, not certifications held by the company.

A Dust Hazard Analysis is a systematic review that identifies where combustible dust is present in a facility, how fire, flash-fire or explosion could occur, and which safeguards are in place or needed. It covers process equipment, extraction systems, building areas with settled dust and housekeeping practice. NFPA 652 requires a DHA for facilities handling combustible dust. Its findings drive decisions on explosion venting, isolation, equipment category and cleaning frequency. A DHA should be completed by a competent person before extraction protections are specified.

Differential pressure is the difference in static pressure measured across a filter, usually shown on a gauge or transmitter on the dust collector. It indicates how much resistance the filter adds to the system. A rising trend can signal filter loading or ineffective cleaning; an unexpectedly low reading can mean reduced airflow, a damaged filter or a faulty sensor. Readings are only meaningful when compared under the same operating conditions with a documented baseline from commissioning. Differential pressure monitoring should be paired with checks of capture at the working point.

Air return, or recirculation, means discharging filtered extraction air back into the building instead of outside. It can save conditioned air, which is attractive in Saudi climates, but it is a design decision that requires a hazard assessment. A particle filter does not remove gases or vapours, and a filter leak would return dust directly to the workplace. Recirculation may need high-efficiency final filtration, monitoring and safeguards, and is unsuitable for some materials. Where air is discharged outside, replacement air must be planned so it does not disturb capture.

High-level cleaning is the removal of dust and debris from elevated surfaces in industrial and commercial buildings, such as roof steel, beams, purlins, ductwork, cable trays, racking tops and light fittings. These surfaces collect dust that can contaminate products, reduce lighting output and, where dust is combustible, fuel a secondary explosion. In Saudi Arabia, DusTech delivers high-level cleaning up to about 20 metres using ground-operated vacuum systems, so most work proceeds without scaffolding or MEWPs and with production areas remaining in operation.

Ground-operated cleaning uses lightweight telescopic carbon-fibre poles connected to an industrial vacuum, with cameras that let the operator see the surface being cleaned, so elevated areas are vacuumed from floor level. Because operators stay on the ground, the method removes most working-at-height risk and avoids scaffolding or MEWPs. Dust is collected rather than blown down, which protects products and equipment below. With ATEX Zone 22 vacuums it can be used in combustible-dust areas. This is the core method of DusTech’s certified high-level cleaning service.

A MEWP, or mobile elevating work platform, is a powered machine such as a scissor lift or boom lift that raises people to work at height. MEWPs are common for elevated cleaning and maintenance, but they require trained operators, ground-bearing checks, exclusion zones and rescue plans, and they often need production areas below to be cleared. In congested plants they may be unable to reach between racking or over machinery. Ground-operated cleaning can avoid MEWP use for many dust-removal tasks, reducing working-at-height exposure and disruption.

SBC 801 is the Saudi Fire Code, part of the Saudi Building Code, which sets fire-protection requirements for buildings and facilities in the Kingdom. For industrial sites it addresses hazardous materials, combustible-dust-producing operations and housekeeping, including the control of dust accumulations on elevated surfaces. Civil Defense inspections reference these requirements. For facility managers, SBC 801 is one reason a documented high-level cleaning programme matters. DusTech plans housekeeping methods with these requirements in mind; SBC 801 is a code reference, not a DusTech certification.

Commissioning is the documented process of proving that an installed dust extraction system performs as designed under agreed operating conditions. It typically includes airflow and pressure measurements at each capture point, checks of controls, alarms and protective devices, and confirmation of safe access for filter service and emptying. Handover passes the system to the owner with as-built drawings, the commissioning baseline, operating and maintenance instructions and operator training. DusTech includes commissioning and handover in its turnkey extraction scope, so the customer receives a verified, documented system.