Plant & Works Engineering

Effective control

Published:  07 January, 2008

Dust emissions are a serious hazard to health and can result in occupational asthma, respiratory disorders and cancer. PWE reports.


There are many sources of dust and chemical pollutants in the industrial and manufacturing workplace environments, such as shot-blasting, soldering, paint spray booths and welding. However, there are other areas which may not seem immediately apparent such as the "normal” office environment.

Inkjet printers are widely used throughout manufacturing and packaging industries to apply information, identification codes and best before dates etc. onto products made from various materials such as glass, card and metal. Some solvents, such as MEK (Methyl Ethyl Ketone), when used as pigment carriers can cause eye and skin irritations, CNS (central nervous system) depression, and is harmful to ingest or inhale. Many modern printers are fitted with local filter and purification systems, therefore protecting personnel from inhaling the solvent fumes.

It is a legal requirement for all companies to comply with The Control of Substances Hazardous to Health (COSHH) 2004 Regulations to control exposure to dust below specified levels. In areas where there are risks of contamination, companies must install Local Exhaust Ventilation (LEV) systems. These regulations also state that the dust extraction plant must be maintained in good working order and tested at least every 14 months.

Some common processes and the legal minimum frequency required for an LEV test:

   Woodcutting (MDF- Hardwood- Softwood)14 Months
   Shot Blasting1 Month
   Grinding of Metals6 Months
   Jute cloth Manufacture1 Month
   Welding (Fumes) 14 Months
   Spraying (Paint)14 Months

There are many types of extraction systems to suit all applications. For example, garage workshops use large, fixed, centralized extraction systems for removal of car exhaust fumes.

Many systems are based on centralized vacuum type arrangements such as low volume woodworking shops, small businesses, bakeries, and smaller vehicle body repair workshops.

Bench-top systems such as soldering stations and other processes may require portable devices to move with the process.

Electrostatic filtration systems is another technology used for fume and odour removal. Typical applications include heat treatment oil quenching, restaurant kitchens, fast food outlets, welding fume removal, training centres and clean rooms.

The contractor chosen to maintain these plants should comply with The CosHH Regulations 2002 Approved Code of Practise (ACoP): "People who carry out examinations and tests on LEV plants must have adequate knowledge, training and expertise in examination methods and techniques.”

The relevant legislation is COSHH regulation 9 and HSG54. Aimed at employers and others who operate, service and maintain LEV (local exhaust ventilation), the codes of practice  provide guidance on the maintenance, testing and examination of LEV systems commonly used to control the release of substances which could be hazardous in the workplace.


Equipment and monitoring

Any fume control system put in place needs to be effective. Although tests are carried out on the actual extraction equipment for correct operation and effectiveness, the main overall driver for installing these systems is to reduce the risk of employee exposure to dusts and fumes. Therefore, measurement of the airborne concentration of dust in the workers breathing zone, to demonstrate the success of the LEV at controlling the hazardous substance, is an important part of the process.

There is a variety of equipment available to measure the exposures.

Personal sampling pumps such as the Apex from Casella can be worn by the individual employees being monitored. They are operated with a sampling head which in turn contains a pre-weighed sampling filter or media. Air is pulled in through the filter at a known rate for up to 8 hours or for a representative time of the process being investigated. The filter is then re-weighed and the total exposure to dust as a mass in mg/m3 can be calculated. This value can then be compared to the Workplace exposure Limits (WEL's) as are laid out in EH40 for specific substances.

If the levels are below the required limit, the LEV system may be working correctly, if not, improvements need to be made or more effective equipment may need to be installed. Another valuable technique is to monitor the dust and fume levels in real time by using a nephelometer or light scattering device.  A typical example of this is the Microdust Pro.

This is a forward scattering IR (infra red) photometer based device which can be used as a hand held instrument to allow real time dust and aerosol levels to be measured, either in the direct breathing zone or in the local vicinity of a worker or their workstation. The unit gives the user a direct readout in mg/m3 and an evaluation on the effectiveness of the control measures in place can be made. Measurements can also be taken to monitor a process before deciding whether any control measures are actually required.

For processes that have potential problems with emissions of solvents and vapours there are also various monitoring technologies that can be adopted. Passive organic sampling badges such as those made by 3M can be deployed.  These are worn by the person and sent off for desorption and analysis of total VOC (volatile organic compound) content.

Other direct reading devices such as PID"s (photoionization detectors) can also be used, allowing samples to be taken around a workplace or station in real time.  Again, this allows for decisions to be made regarding appropriate control measures.

Even after control measures have been installed, if any changes are made to the process or operation, or use of different materials, further monitoring should be undertaken to ensure the health of the operators are not at risk.

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