Industrial Combustible Dust

Industrial Combustible Dust:

Occupational health should aim at the promotion and maintenance of the highest degree of physical, mental and social well beings of workers in all occupations. Now a days it is observed that dusting level is gradually increasing due to growth of industries throughout globe and combustible dust which causes serious occupational health related issues to workers in industries is a serious concern for industries. Successful occupational health & safety practice requires the collaboration and participation of both employer & workers in health and safety programmes and involves the consideration of issues relating to occupational medicine, industrial hygiene, toxicology, education, engineering safety, ergonomics, air contaminants, physiology, psychology etc…

What is combustible dust: It is defined as a solid material composed of distinct particles or pieces, regardless of size, shape, or chemical composition, which presents a fire or deflagration hazard when suspended in air or some other oxidizing medium over a range of concentrations. Sometimes it is known as explosion hazard and there may be chances of increasing fatal ratio & unwanted serious incidents. There are five elements necessary to initiate a dust explosion. These are: - 1. Combustible dust (Fuel) 2. Ignition source (Heat), 3.Oxygen in air (oxidizer), 4.Dispersion of dust particles in sufficient quantity and concentration 5.Confinement of dust cloud. First three are known as fire triangle. When dust is exposed to enough heat or even a spark, it can ignite. When airborne dust is near a fire, it often results in an explosion. Poor work procedures can stir dust into the air, and something as simple as a spark from welding or a hot machine motor or bearing, for instance, is all it takes to trigger an explosion. If one of the above five elements is missing, an explosion cannot occur.

Industries handling combustible dust: Many materials can become combustible under specific situations as :

  • Agriculture
  • Food Products
  • Chemicals
  • Textiles
  • Forest and Furniture Products
  • Metal Processing
  • Tyre and Rubber Manufacturing
  • Paper Products
  • Pharmaceuticals & bio solids
  • Wastewater Treatment
  • Recycling Operations (metal, paper, and plastic)
  • Coal Dust – Coal Handling and Processing Operations
  • Other carbon dust
  • Plastic dust & additives 

Conditions needed for a dust explosion to happen:-

The basic requirements for a dust explosion to occur are that combustible dusts are suspended in air and are ignited. In practice, for a dust explosion to occur, a number of conditions must be met including:

  • The dust must be combustible and release enough heat when it burns to sustain the fire
  • The dust must be capable of being suspended in air.
  • The dust must have a particle size capable of spreading the flame.
  • The concentration of the dust suspension must be within the explosive range.
  • An ignition source must be in contact with the dust suspension.
  • The atmosphere must contain sufficient oxygen to support and sustain combustion.
  • There is a form of confinement or enclosure that allows pressure to build. 

Control Measures:-

  1. There should not be any leakage from ducts & dust collectors.
  2. There should not be any fugitive dust to accumulate in the work area.
  3. Regular cleaning of floor surfaces.
  4. Regular housekeeping of ducts, pipes, ledges, beams to minimise dust accumulations.
  5. Adopting Ignition control measures during cleaning thru devices like vacuum cleaners etc. & Utilizing the preferred method of vacuuming with appropriately rated Class II vacuum cleaners that are bonded and grounded to minimize accumulation of static charge
  6. Display of safety posters like” No Smoking”
  7. Facility has work permit system- cold work, Hot work, Electrical isolation work permit etc..
  8. Duct systems, dust collectors, and dust-producing machinery are bonded and grounded to minimize accumulation of static electrical charge
  9. Available of MSDS related to combustible dust and to follow MSDS.
  10. Training to employees on the explosion hazard of combustible dust.
  11. Awareness & preparedness measures like tool box talk & mock drill for explosions
  12. Facility should have emergency exists, well ventilation, adequate firefighting system,
  13. The facility should have separator devices to remove foreign materials capable of igniting combustible dusts.
  14. Facility should have an emergency action plan and assembly points.
  15. Conducting mock drills as per set plan.
  16. Discussion regarding incidents & investigations related to combustible dust in safety committee meetings.
  17. The facility should have isolation devices to prevent deflagration
  18. The facility should have isolation devices to prevent deflagration propagation between pieces of equipment connected by ductwork
  19. The dust collector systems should have spark detection and explosion/ deflagration suppression systems
  20. Workers have the proper respirators, mask and protective clothing
  21. Written procedures – SOP/OCP/WI for operations, maintenance and training
  22. Gentle sweeping with soft brooms or brushes with natural fibre bristles and water wash downs is generally permitted as well
  23. Regular review of workplace monitoring, equipment like smoke detectors & other gas detectors, flame proof light arresters fitted at chemical storage areas.
  24. Hazop study and regular review of hazard identification & risk assessment (HIRA) with control measures of entire processes/activities.

TUV India Pvt. Ltd. -Subsidiary of TUV NORD GROUP is providing various industrial services like inspection, testing, second party audit and various management system certifications. TUV India also provides safety audits in all type of industries to find out potential hazards across the processes & activities through safety experts. TUV India also supports by providing different types of safety related trainings through competent persons.

About The Author

Abhaya Kumar Das

Senior Lead Auditor - IMS & EnMS
TUV India Pvt Ltd