Egmont Air understands that each industrial workspace has unique challenges when it comes to managing dust and fumes. To help you identify and resolve potential air quality issues, we follow a 9-step process for analysing dust problems in your workplace. Our process ensures that your dust and fume extraction system is tailored to meet your specific needs and provide a long-term solution to improving air quality and worker safety.

Why Analysing Dust Problems is Crucial

Dust problems in industrial environments are not only a health risk but can also negatively affect productivity and the longevity of equipment. Without proper dust control, workers can face serious respiratory issues, machinery can suffer from damage, and operations can experience costly delays. Analysing dust problems is the first step in ensuring that your dust and fume extraction system is effective and compliant with health and safety regulations.

The 9 Steps to Analysing Dust Problems

To develop the most effective solution for your workplace, Egmont Air follows a detailed 9-step process for analysing and addressing dust-related issues. Here’s how we approach every project:

Step 1 – What is the Composition of Dust or Pollutant?

Dust particles range in size from sub-micron to 100microns or even larger. Dust may also have properties that affect its pneumatic transport, handling, filtration and storage such as: hydroscopic, carcinogenic, explosive, corrosive, compostable, combustible, electrostatic, sticky, damp, hazardous, etc. A full understanding the dust composition is important for correct selection of filtration and what precautionary measures (such as Atex) may be needed in designing the dust extraction system.  OSHA define dust particles with an effective diameter of less than 420 microns as combustible dust and of greater risk of Fire and Explosions, click here for more information.

Step 2 – How is the Dust Produced and to What Extent?

Dust and pollutants are usually created by a process such as conveying, shakers, screening, decantation, blending, mixing, pouring, etc and therefore often disperse with a certain amount of kinetic energy especially if heat-induced or projected from a saw-blade or abrasive wheel with high peripheral speed.

Analysing the rate or velocity of dispersal is important in calculating airflow rates to capture the dust before it spreads into the workers breathing zone or pollutes the environment. Consideration of operator movement, gantry-crane, or vehicle access may also limit the ability to locate hoods close to the source of dust and require unique solutions and design to allow productivity and processing to occur.

Finally the volume of dust to be collected is always important when calculating dust-loading on filters, collection method and maintenance service intervals to ensure the system will perform reliably in years to come.

Step 3 – Site Location and Operating Duty

Consideration of location and operating duty is important to ensure local regulations are complied with for clean-air discharge, hazardous zoning, resource or building consents, storage, handling and control of substances, noise restrictions, etc.

Localised factors which may influence the operational performance of a dust extraction system such as humidity, temperature, and elevation can have a consequential effect on the fan duty and resultant airflow which may need to be compensated for.  These factors also affect filtering performance where insulation or heat-tracing maybe required in extreme cases, but at least, selection of the correct filter media to ensure a guarantee of clean-air discharge will need verification.

Operating duty also considers the hours of operation, dust-loading, continuous-running-time (elapsed time) which will affect the dust extraction design. Larger filters, automated on-line cleaning, decantation chambers, and the like are features which can be specified to overcome unique operating duties found in some factories.

Step 4 – How to Capture Dust?

This is where the design of the dust extraction system begins, common solutions include the use of hoods placed close to the source, and always preferably in-line with the direction of pollutant trajectory.  Sometimes this isn’t possible and side-draft airflow movement can be calculated for a grinding-booth or sanding-bay type environment, downdraft suction benches also work well for some processes and at a last resort a high air-change ratio can be specified for general air-cleaning affect.

Hood-size and distance from source are the two prominent factors that determine capture velocity and overall air-volume required to capture dust at source. Minimum air velocities required at point of origin to capture gas or vapour effectively can range from 0.25-0.5m/s when released without noticeable movement, or 0.5-1.0m/s when released with low velocity.  Airflows can be calculated for an unobstructed hood using the formula.

Q = V₁ (10X² + A)
Where

Q = quantity of air exhausted in cubic metres per minute

V₁ = air-velocity at X-distance, m, from the hood and on the centreline of hood, in metres per minute

X =  distance along the hood centreline, m, from the face of the hood to the point where the air velocity is V₁ m/min, Valid for X less than 1.5 pipe diameter.

A = aera of the hood opening, in square meters

An increase in airflow or hood-size (over and above standard formulas) maybe required where the behaviour or characteristics of a pollutant require it to ensure it is captured successfully.

Step 5 – Type and Capacity of Filtration?

With the advancements of technology there are a massive range of filtration devices available for dust and fume extract systems in industrial manufacturing applications. The type and size of filtration and filter media will depend primarily on three main factors:

• Type of dust or pollutant
• Volume of dust-loading and operating duty
• Airflow

The most common comparative ratio used for filter sizing is know as ‘Air-to-Cloth’ ratio or Air Permeability.

To calculate the air-to-cloth ratio simply divide the air-volume by filter-media area :

ft³/min  ÷  ft² =  air-to-cloth ratio

For example: a dust collector with an airflow of 6000cfm over a filter area of 3000ft² has an air-to-cloth ratio of 2:1 this means each square foot of filter media is processing two cubic feet of air per minute.  The higher the ratio the more airflow is passing through each square foot of filter media and the less effective it will be in the long term.

Correct filter sizing is essential to ensure reliability of the system and that the filters can self-clean or decant dust without binding (filter blocking). A conservative ratio may mean a higher initial investment, but much better suction and lifetime performance with lower consumable and maintenance costs. Conversely, a high ratio will result in a higher pressure-drop across the filters resulting in the need for oversizing fans, and invariably, increased operational costs and downtime.

Obviously specifying the correct ‘filtration efficiency’ for each application is critical to ensure that the pollutant is captured and filtered successfully to ensure clean-air discharge and compliance with local regulations.

Common types of filter systems for dust and fume extract systems in industrial manufacturing applications include:

• Baghouses – Typically used in the wood working industry, fitted with bags, pocket, or fabric filters which prove very effective for filtering large volumes of dust/shavings and a wide range of particle sizes.
• Cartridge Dust Collectors – very effective for sub-micron and small particles such as smoke, fume, and fine powders.  Often pleated to achieve a high filter surface area but do have limitations processing higher volumes of pollutants.
• Cyclones – comparatively low efficiency method of filtration which uses centrifugal force to separate particles from the air-stream. Due to the lower filtering efficiency, they are often used as a pre-separator to a secondary filter-media type system.
• Wet Scrubbers – usually reserved for special applications where hot gases, sticky fibres, or liquid (humid dusts) require filtration. These do require relatively high maintenance and water-usage and treatment of waste water needs to be considered when specifying this type of filter
• Electrostatic Filters – use electrically charged plates that capture pollen, kitchen fumes, and allergen particles by charging the particles and attracting them to plates. The plates must be cleaned frequently as a build-up of particles on the plates reduces filtering efficiency.
• Activated Carbon – works by absorption of impurities onto the surface of the activated carbon, particularly good for organic compounds and removing odours, gases and other contaminants from air or gas. Activated carbon does have limitations particularly where changes in humidity may cause the activated carbon to release contaminants to re-enter the atmosphere.
• HEPA filters – also known as ‘absolute filters’ are made of extremely fine fibres formed in a mesh-like lattice that traps pollutants and discharges sterilised air. These filters are very restrictive to airflow and typically reserved for use in food industry, pharmaceutical, medical applications, etc.

This, by no means, is a complete list of all the industrial type of filtration systems available. We recommend a consultation when selecting the most appropriate filter system for each individual application.

Step 6 – Dust Collection

Final collection and disposal of the pollutants is an important decision to be made, after all, many dusts and pollutants are regarded as hazardous and must be handled safely and disposed of according to local regulations.

Bins, drums, containers, bags, are all common methods of capturing dust particles, but often overlooked, is the practicality of emptying these collection devices without creating a secondary health hazard.  Drums and containers needed to be appropriately sized for the volume of dust to be collected as well as practicality of emptying.

Some products such as wood dusts and shavings, metal dusts, cardboard, polystyrene, etc can be recycled using a briquette press to compact the waste into regular shaped briquettes for further processing.  Along with Chippers and Shredders, Briquette machines can be integrated as part of the dust extraction system.

Step 7 – Conveyance & Ducting System

Once the airflow and filtration system are decided, conveyance of particles is usually required in the form of sheet-metal or pipe ducting to allow transport of the captured particles at source (via hood or plenum) to the centralised dust collector which may often be located remotely.

Ducting sizing needs to be done carefully to ensure that the air travels at a constant speed throughout the system to avoid blocking or conversely excessive power consumption to convey the particles.  Typical velocities used in most dust extraction systems operate in the 20-25m/s range although lower velocities can be used for gas and fume applications, whereas higher velocities maybe required for heavy density dusts with low aerodynamic properties.

What this means is that the ducting sizes need to vary as additional branches or outlets are added to the main-line which increases the ducting cross-sectional area as it routes towards the dust-collector and fan system.

If the generation of dust volume is excessive, such as high-speed planners producing incredible volumes of wood shavings, then air-saturation calculations must be done to ensure that there is enough air-volume to transport the mass of product.

Due to the high velocity of air in dust extraction systems, ducting needs to be constructed from heavy-gauge material with long-radius bends and low-angle branches for smooth and low-resistant passage of contaminants. For that reason, air-conditioning and ventilation type ductwork is regarded as unsuitable for dust extraction systems.

The route of ducting should be as straight as possible and minimising bends where practically feasible. Each metre of duct and each transition of airflow creates resistance (pressure-drop) which absorbs power that the fan must be designed to overcome.

Step 8 – Fan Size and Selection

The Fan is what makes it all happen!  Fan size is primarily based on two factors of Airflow and Pressure.  These work in opposition to each other, in other words, for any given fan, as airflow goes up, pressure comes down, and vice versa, as pressure goes up, airflow comes down.

In dust extraction terminology, the term ‘pressure’ is typically used as a definition for both positive or negative (vacuum) pressure expressed in Pascals or inches of water-column. Essentially, we are referring to the difference in pressure (positive or negative) between the inside of the extraction system and atmospheric pressure, or the amount of resistance a component of the extraction system may create.

The job of a dust and fume extraction specialist is to calculate both the airflow required (as mentioned in Step 4) along with the loss-of-pressure (resistance) that will occur in the system and plot both of these, to determine the fan duty and size required.

If either more airflow, or more pressure (resistance) is required, a larger fan will need to be specified to meet the duty to capture and transport the pollutants without blockages.

Each metre of duct and each transition (bend, branch, etc) of airflow creates resistance (pressure-drop) which absorbs power that the fan must be designed to overcome. Along with this, the filters also create resistance as well as losses due to the friction of moving air under vacuum or pressure.

For nearly all dust extraction systems a Centrifugal type fan is used as these generate ample pressure for lengthy ducting lines and high velocity. In some low-velocity fume extraction systems (such as spray-booths), an Axial fan may be used which produces high volumes of air at lower operating pressures.

For most extraction systems the fan is placed beside the filter system (or as an integral part of it) to provide vacuum through the duct-work system.  The fan can be placed on the clean-side (after the filter) or dirty-side (before the filter) providing the fan is capable of processing the contaminated air.

The impellor type will be selected according to the duty (airflow/pressure combination) required and with respect of any contaminates that may be passing through the fan. The most common types of centrifugal fan impellors are:

• Airfoil – the highest efficiency of all centrifugal fans, the impellor blades contour away from the direction of travel and the profile of the blade is similar to an aeroplane wing which provides the best airflow performance. Airfoil fans are usually expensive and not often used.
• Backward inclined – (or Backward Curved) are the same as Airfoil fans except the blades are flat single thickness. These produce very good performance and are the most common impellor type used in dust extraction systems. They are limited to processing material that is dry and of short length, not long stringy or fluffy material.
• Radial – Simplest of all centrifugal fans and least efficient but has high mechanical strength particularly used for materials that maybe problematic to convey such as wet, stringy, or abrasive materials, impellor is usually self-cleaning to some degree.
• Forward-curved – Medium efficiency and usually fabricated of light-duty materials and low-cost construction, best used in applications where placed on clean-air side of filters.

For hazardous zones and materials or air-streams, special fan design, construction and specification must always be used, please consult a dust and fume extraction specialist for advice on these applications.

Most systems these days are installed with ‘Variable Speed Drives’ (VSD). When coupled with a pressure transducer the fan will automatically ramp up/down depending on the number of outlets open at any one time providing a massive saving in power.

When any centrifugal fan is slowed down 20% it provides a massive saving in power of approx. 50% due to the physics of fan law.

This is particularly applicable to dust extraction systems for Joinery and Cabinetmaking workshops where multiple machines are connected to one central dust extraction system however only a few of the machines maybe used simultaneously. This means the fan will automatically ramp up/down in speed to provide optimum suction for the machines and outlets open at any one time, while providing considerable savings in power consumption.

Conversely increasing fan-speed (rpm) has a drastic increase in power and noise. Power increase is expressed as rpm³ meaning that a 10% increase in rpm requires a 33% increase power absorption.  Silencers, fan enclosures and other acoustic devices can be specified to provide noise attenuation.

Step 9 – Professional Advice & Compliance

Egmont Air Ltd always recommend you seek professional advice which is readily available from companies specialising in dust and fume extraction. Dust and Fume Extraction is often regarded by some as ‘an unknown magic’ however the law of physics and first principles of dust and fume extraction can be applied to solve any dust problem or fume issue in today’s manufacturing environment.

This 9 Step process is not intended as a comprehensive procedure, rather an introductory outline of dust and fume extraction. Resources and publications such ‘Industrial Ventilation A Manual of Recommended Practice’ published by ACGIH offer more detailed guidance on the design, operation and maintenance of industrial extraction systems, click here for more information.

Consultation with industry professionals and local authorities is also highly recommended to ensure any dust and fume extraction system is designed in compliance with local and international standards particularly where hazardous or combustible materials may be involved.

The Benefits of a Thorough Dust Problem Analysis

By following this 9 Step Process to analyse your dust problems, we ensure that the solutions we provide are both precise and effective. Here are some key benefits of our approach:

• Tailored Solutions: Every workplace is different. Our 9 Step dust problem analysis allows us to create a custom dust and fume extraction system that’s specifically suited to your needs.
• Improved Health and Safety: With a clear understanding of your dust issues, we can design a system that effectively reduces health risks for your workers, helping to prevent respiratory diseases and other long-term health issues.
• Enhanced Productivity: Reducing dust exposure can improve worker comfort and focus, leading to better productivity and fewer sick days.
• Long-Term Cost Savings: By addressing dust problems at their source and ensuring your system is optimised, we help you avoid costly downtime and equipment maintenance.

Take the Next Step in Analysing Your Dust Problems

If you’re concerned about dust problems and fume issues in your workplace, it’s time to take action. The first step is a comprehensive dust problem analysis. At Egmont Air, we’re committed to providing the expertise and solutions you need to ensure a safe and healthy work environment.

Contact us today to schedule your consultation, and let’s work together to identify and solve your dust and fume challenges.