A3.10.5.2 Control of Particulate Emissions


Particles, such as grit, dust and fumes can be eliminated through production processes or controlled in that they are not allowed to become airborne, or that they are separated from the air.


Preventing Particles Emissions

The first stage of reducing air pollution is to eliminate the cause of the air pollution.

  • Production Processes
    • Eliminate the use of powders in the production process. For example, rather than using dry powders, purchase the materials in a solution or purchase them in a solid form and create a solution.


Preventing Particles becoming Airborne

Where it is not possible to prevent the creation of particles, you should ensure that the production process does not allow the generated dust or grit become airborne.

  • Water Spays
    • Water mists may be used on dust to force it to settle. For example, this is commonly used on dusty construction sites.
  • Enclosures
    • Contain the contaminated air in an enclosure or hood. This may then be extracted using duct work and fans. This is commonly used in woodworking environments (extractor fans)
  • Settling Chambers
    • Large particles will eventually settle to the bottom of an enclosed area. To aid this, the flow of air must be sufficiently slow to allow the dust particles to drop out of the air flow. These settled particles can be collected in units such as hoppers.


Removal of Particles from Air

If it is not possible to prevent such particles being generated, or preventing them from becoming airborne, the particles should be separated from the air.


  • Centrifugal Separators
    • A centrifugal force is created by a spinning gas stream. This separates the particles from the gas stream, where they are thrown to the walls of the centrifuge and subsequently fall into a collection hopper.


  • Wet Scrubbers
    • Use a liquid to wash out particles. The particles form a slurry, which can be disposed of. These are of more use in confined processes, where the air does not need to be returned to the workplace.


  • Wet Electrostatic Precipitator
    • A wet electrostatic precipitator operates with saturated air streams (100% relative humidity).
    • One type uses a vertical cylindrical tube with a centrally-located wire electrode (gas flowing upward) with water sprays to clean the collected particulate from the collection surface (usually plates or tubes).
    • Another type is used for coke-oven gas detarring, which uses a falling oil film to remove collected material.


  • Fabric Filters
    • A fabric filter is used to separate out the particles from the air (similar in function to how a sieve prevents large particles from passing through it). The filters will become blocked and require regular maintenance, such as mechanical shaking to disperse the particles or a pressured air stream being applied from the reverse to remove the particles.


  • Electrostatic Precipitator
    • Electrostatic Precipitators are particulate collection devices that remove particles from a flowing gas (such as air) using the force of an induced electrostatic charge.
    • The charged particles are attracted to electrodes and therefore removed from the air.
    • Electrostatic precipitators are highly efficient filtration devices that minimally impede the flow of gases through the device, and can easily remove fine particulate matter such as dust and smoke from the air stream.
    • In contrast to wet scrubbers which apply energy directly to the flowing fluid medium, an Electrostatic Precipitator applies energy only to the particulate matter being collected and therefore is very efficient in its consumption of energy (in the form of electricity).