Dust

Why dust is a problem

Dust can cause explosions.

Textile process dusts, in particular wool and cotton, can also cause byssinosis (cotton dust), occupational asthma and respiratory irritation – see more information below (link to more info below).

Up-to-date COSHH assessments, control to within Workplace Exposure Limits (WELs) and simple health surveillance are priorities where dust is a hazard.

For the wool industries typically dusty operations include opening, blending, carding, and backwinding.

For cotton, control measures are likely to be required for most early processes including raw material handling, opening, carding, drawing, combing, beaming, ring spinning, and high speed winding.

Cleaning should be done using something like a vacuum cleaner, not a broom or brush or compressed air.

More information about WELs - Workplace exposure limits

Byssinosis - an illness associated with exposure to cotton dust with both acute and, in some cases, long-term effects.  The numbers of compensated cases have been in single figures for more than the last decade (Table IIDB05).  The number of death certificates per year with byssinosis recorded as the underlying cause of death has been also low in the last decade; typically, there have been fewer than five deaths and in 2009 there were 2 deaths (Table DC01)

Further information

• Lung diseases
• Chronic obstructive pulmonary disease (COPD)
• Local exhaust ventilation (LEV), workplace fume and dust extraction

Controlling risks from dyestuff dust

Dust from dyestuffs used in textile finishing can be harmful to health.

The starting point should be to stop the dust being generated altogether. Whenever possible, try to handle dyes in dust-free or reduced-dust forms, for example, in solution, as granules, pellets, pastes, or dedusted powders, rather than as dry powders. Contact your suppliers for advice.

Where you can't avoid handling dyes in their dry powder form, try to reduce the amount of handling to a minimum. It may be possible to eliminate some stages in a process, for example, by:

• buying pre-weighed quantities;
• weighing dyes directly from the original containers rather than from storage bins;
• dissolving dyes under local exhaust ventilation (LEV) immediately after weighing;
• weighing into process-compatible, water-soluble bags

Working carefully with the dye powder product can reduce the amount of dust released considerably, so provide training in good handling practices.

Housekeeping

• Containers - use robust containers with a closable lid for storage.  However, repeated removal and replacement of container lids and opening and closing of bags can also generate more dust. Plan to dispose of containers safely. Bags especially can cause problems and are best placed into disposal sacks at the workstation, under LEV. Also plan how you will deal with damaged containers and how to dispose of unwanted dyes.
• Areas where dyes are handled should be easy to clean, with walls and floors that are sound and smooth. Rounded corners are easier to clean.  Shelving and workbenches should be easy to clean too or else covered with impervious, disposable covering.  They should have a lip to retain spills.
• Cleaning and dealing with spillages - dry vacuum cleaning, using a piped system or a type H industrial vacuum cleaner, is best for larger dry spillages and most cleaning tasks.  Wet vacuuming or other wet cleaning methods may be appropriate in some situations or for smaller spillages.  Don't use brushes or brooms or compressed air, as these will simply spread the dust into the air.

Personal protective equipment (PPE)

• PPE should only be used to protect workers as a last resort and in addition to other controls where it isn't reasonably practicable to fully control the dust by other means. Take care when choosing PPE and make sure that it is appropriate for the work.  PPE should be used properly and maintained in good condition.
• Coveralls of close-weave fabric (or suitable disposable ones) should be worn when handling dyestuffs.
• Gloves and aprons may be needed for some jobs. These should be impermeable and either disposable or cleanable.  They should be removed when not needed because they may be a continuing source of dust if contaminated.  Workers should remove gloves and aprons in a way that does not contaminate skin or clothes.  Take a look at the following web pages for how to do this:
  • Removing gloves without contaminating hands
  • Removing single-use gloves without contaminating your hands
• Respiratory protective equipment (RPE) may be needed for short-duration jobs, such as filter changing.  RPE should be carefully selected to provide adequate protection. It needs to be suitable for the wearer as well as for the task. Correct fitting is important and suppliers can help by offering face-fit testing. Beards and stubble growth prevent a good fit and facemask type respirators cannot be used in these circumstances. Where suitable for the wearer, disposable respirators giving protection against fine particulates (EN 149) to at least 10 times the occupational exposure limit will be adequate in most circumstances, but should be selected following an assessment.

More information can be found at:

Respiratory protective equipment (RPE)

More information about safety with dye dust can be found at Dyes and dyeing.

Cotton and wool process dusts

Exposure to cotton dust has long been associated with the chronic respiratory disease byssinosis.  The incidence of the disease is related to the number of years a person is exposed to the dust and the concentrations of airborne dust to which they are exposed.  Most cases are associated with earlier parts of the processing where dust levels are generally higher.  It is not known which component (or components) of the dust cause the disease.  However bleaching or other wet treatments reduce the incidence of the disease.

Illness associated with exposure to wool dust is less well defined.  Typically, chronic bronchitis, breathlessness, persistent rhinitis (runny or stuffy nose) and persistent conjunctivitis (itchy or sore eyes) are seen.  The incidence of these symptoms is related to concentrations of airborne dust and to the number of years a person is exposed.  There does not appear to be a link with any particular stage of wool processing.  It is not known which component (or components) of the dust cause the disease.

The WEL for cotton dust is 2.5 mg/m³ (8-hr TWA) and  applies to exposure to inhalable dust during the handling of raw and waste cotton including blends containing raw or waste cotton, with the following exceptions:

• dust from weaving, knitting, braiding and subsequent processes;
• dust from bleached or dyed cotton; and
• dust from finished articles, for example garments.

The MEL for wool process dust is 10 mg/m³ (8-hr TWA).   Wool process dust is the term used to describe the dust generated in the production of woollen and worsted textiles.  This includes all factory processes from the receipt of the raw wool up to the finished product in the case of carpet manufacture and up to, and including, weaving, knitting or non-woven cloth production.  It does not cover agricultural processes, including any sorting or baling done on the farm.  The term 'wool', in this case, refers to sheep's wool and wool blends only.  It does not include other speciality fibres - such as goat hair (including cashmere and mohair), camel hair or alpaca.  These fibres differ from wool in structure and it is not certain that the composition of the dust or the potential health risk is the same as with wool process dust.

Where a WEL does not apply, dust exposure should still be adequately controlled.

More information about WELs can be found on the following webpages:

• Workplace exposure limits
• EH40/2005 Workplace exposure limits

Control of dust exposure

It isn't possible to eliminate process dusts from mills but it may be possible to reduce the quantity of dust produced.  Batches of cotton and wool vary in their dustiness, depending on the quality of the raw material, the treatment it receives and the processes through which it is put.  You should consider the reduction of dust as one of you objectives when introducing new processes or machines or when changing existing ones.

Control of exposure to dust has to be achieved without the use of respiratory protective equipment (RPE) if this is reasonably practicable.  Often the most effective approach is to enclose machinery as much as possible and then to use LEV to control dust escaping from essential openings.  Good general ventilation is necessary to prevent the build up of high background dust levels.  Exposures can also be reduced by removing workers from close contact with the process, for example by eliminating the need to enter blending bins or by placing workers in booths fed with filtered air where this is feasible.

Cleaning machinery by 'flapping down' with cardboard or by using compressed air is strongly discouraged as high levels of dust can be generated by disturbing settled dust.  A better alternative is to vacuum with a type H cleaner suitable for industrial use or to use a a piped vacuum system.  If brushing floors cannot be avoided, then dust generation can be reduced by first moistening the floor with a water spray.

The filters in dust collection systems will either be under positive or negative pressure depending on whether the fan is on the dirty or clean side.  Filters under positive pressure (blown filters) should be enclosed or located in a separate filter room since any leak in the filter will cause dust to be blown into the working area.  Any air returned to a workroom from a dust collector should not significantly increase the exposure of workers.  Dust concentrations in returned air may need to be further reduced using a high efficiency secondary filter, water spray scrubbers or electrostatic precipitators.  Determination of the appropriate measures is a matter for specialist advice.

Unless the system is designed with rotary valves to be emptied while running, dust collectors should be emptied with the system switched off and using a method which prevents the release of dust.  One option is to use a disposable bag in a collector bin.  Emptying dust collectors is a very dusty task and RPE should be worn if dust cannot be adequately controlled during emptying. A failure to ensure filter systems are regularly emptied and well maintained will lead to a dropping-off in their performance and will make their eventual emptying an even more difficult and dusty task.

Guidance on removing waste from a dust extraction unit can be found at the following links:

• General ventilation
• Engineering controls
• Removing waste from a dust extraction unit

Control of dust - common to both industries

16 All manual handling of raw materials (for instance pulling from bales; carrying and dropping or throwing) is likely to expose the worker to significant levels of dust. The inflowing air at a vacuum conveyor, or any LEV provided at the feed point of opening machines, will not significantly reduce the exposure of the person feeding the material manually. Therefore, the aim should be to reduce the amount of manual handling to a minimum. Some handling may be eliminated by changes in working practice. Automation may also be feasible; in the cotton industry automated bale pluckers fitted with extraction have reduced operator exposure significantly. LEV may be practicable in some instances, eg at sorting tables. For some manual operations adequate control of exposure may only be achieved by using RPE in addition to other measures.

17 Maintenance jobs often result in high exposures because employees are working in close proximity to dusty machinery often with the enclosures removed, disturbing settled dust and with no LEV. Exposures can be reduced by removing dust from machinery by vacuum cleaning as far as possible before work starts. Where there is a permit-to-work system, cleanliness of the machine should be one condition of entry on the permit. Respiratory protective equipment may be needed to adequately control exposure.

18 Travelling push-pull cleaning systems are used on some spinning and winding processes. These aim to increase the quality of the yarn by blowing material off machines and then vacuuming up the settled material at ground level. They are not designed as exposure control measures and their effect is variable. In some instances local dust concentrations in air will be increased.

Control of dust - cotton industry

19 Opening and blowing room machinery, eg scutchers, should be fitted with LEV unless there is pneumatic transfer between machines creating enough negative pressure to prevent the escape of dust from the machines. Manual opening and lapforming are likely to generate exposures which exceed the MEL.

20 On older carding machines the original system for providing LEV at the most effective points, the Shirley Pressure Point System, can still be effective. However, higher production rates have increased the amount of dust produced and for any poorly enclosed machine working at high output, an LEV extraction figure in the region of 50 m3/min/card (1750 cu ft/min/card) is recommended as a guide. Lower production rates, greater enclosure and well-designed LEV are all factors which may justify a lower extraction figure. For newer machinery, the supplier should specify an appropriate rate. Under-machine extraction located inside the enclosure will remove settled waste and trash and should be provided.

21 Trash removal, especially from blowing, opening and carding plant should be by vacuum methods. Manual clearance of trash creates a great deal of dust and would lead to exposures generally exceeding the MEL.

22 LEV at drawing, combing and speed frames is now almost standard and has significantly reduced the exposure of operators. Whether suction systems for automatic take-up of broken ends improve exposure levels is less clear.

23 Exposures at ring spinning vary depending on the count of the cotton being spun. Where low and medium count cottons are spun, exposures may be high. These processes are described as ring doubling or balling in some mills. Local exhaust ventilation can be fitted but will require careful design. Under-floor extraction at spinning processes is effective as part of the general ventilation.

24 Open-ended spinning generally results in operator exposures lower than the MEL as the process itself has to be enclosed and under negative pressure. In addition, less operator attendance is needed.

25 The high speed operation of winding and doubling can produce high exposures above the MEL especially with low grade cotton and poor control measures. The requirement for close supervision will generally limit the application of LEV.

26 Beaming machines create movement of large quantities of entrained air which makes effective control of dust by LEV difficult. Unless extraction is provided, dust carried on the induced air flow from the creel to the beam will collect in the stagnant area just beyond the beam. This is usually where the beaming attendant stands. A fixed receptor hood, with screens, fitted above the beaming machine headstock can be an effective method of control, provided it removes the necessary large volumes of air. General room ventilation moving air in the same direction as the induced air flow to extraction sited beyond the beam may also be effective, since it prevents stagnation of the dusty air. Experience shows that it is possible to reduce exposures to below the MEL at beaming through the provision of good general ventilation. If it is not possible to provide enough ventilation, a less satisfactory approach is to move the operator to one side of the beam and provide a booth with filtered air supply. Respiratory protective equipment would then be worn during times outside the booth.

Control of dust - wool textile industry

27 All willying machinery is capable of being enclosed and, where necessary, provided with LEV at essential openings. Assessment of working practices should ensure that manual handling of the raw material is kept to a minimum. Nevertheless, RPE may need to be worn by operators who feed material from bales manually. Fibre is often conveyed pneumatically at early processing. Efficient systems will be needed to separate the fibre from the high volume of conveying air before this is vented at the delivery point.

28 Dust exposures are high or very high in traditional blending bins where the bins are emptied manually. Vacuum conveyor systems within the bin do not provide significant capture of dust. The process is not amenable to engineering control and the use of RPE is essential. Wherever the opportunity arises bin emptying should be automated, through the introduction of moving bin emptiers or similar plant. In both automated and traditional blending bins, dust may build up on bin roofs. To prevent this, some bins are now fitted with canopies over the perforated ceiling which exhaust to a dust filtration system.

29 The dust generated at carding processes will vary considerably with the dustiness of the blends being processed and the speed of the machine. The decision on what measures are reasonably practicable will depend on an assessment of exposure, taking into account the most dusty blends which are processed. Dust emissions can be reduced by the provision of close fitting covers to those parts of the machine throwing off dust. Further improvement can be made by fitting extraction to the covers. The covers would be in addition to, and not in substitute for, perimeter fencing. Respiratory protective equipment may be required for certain operations such as manual fettling. Vacuum fettling systems have the added advantage that they can be extended to provide vacuum cleaning for other parts of the workroom.

30 Backwinding in carpet yarn mills is a process producing high exposures. Control is complicated by the constant close attendance needed from operators which makes enclosure difficult, and by the many sources of dust. Nevertheless, there are a number of ways in which the problem can be tackled:

1. Machinery: Some designs of frame generate less dust than others. This should be borne in mind when purchasing new or reconditioned machinery.
2. LEV: Some success has been achieved using LEV systems designed to create air flows to carry the dust away from the operator. It is essential to position the extraction as close to the machines as possible.
3. Process factors: Excessive drying should be avoided as this seems to be significant in increasing the amount of dust generated.
4. Yarn: Some batches of yarn are much more dusty than others. If these can be identified, it may be possible to process these yarns on a few designated frames equipped with engineering control. They could perhaps be processed in a segregated area or on a particular shift, to reduce the number of employees exposed. In these latter cases, it would be essential for the employees involved in processing to be further protected by RPE.
5. Working practices: Compressed airlines should not be used to blow down frames.

31 Whilst opening, blending, carding and backwinding are likely to produce the highest personal dust exposures, many other processes also generate dust. Even if personal exposures at these processes are likely to be below 10mg/m3 (8-hr TWA) the significance of the MEL is that all reasonably practicable measures should be taken to reduce dust exposure yet further.

Choice of respiratory protective equipment

32 Respiratory protective equipment should only be used when the dust levels have been reduced as far as reasonably practicable using other methods. When calculating the relative costs of engineering controls and RPE, long-term costs should be used. Initial costs of RPE may be comparatively low but the cost of replacement and maintenance must be added. Situations will vary, but equipment lifetime costs often show RPE to be the more expensive option. If RPE has to be worn then in most instances the choice will be between filtering face-piece respirators (FFP or 'disposable'), half-mask respirators, or powered visor respirators. Each type has its merits but powered visor respirators have the advantages of: higher protection offered by some models (if needed), integral hard-hat (if needed), no face-fit required, and greater wearer comfort over longer periods.

33 All RPE supplied since 1 July 1995 should be marked with a CE symbol (this means it meets European Union requirements, usually conforming to a European Standard). Equipment which was HSE 'type approved' and was manufactured before July 1995 may still be used if it is serviceable. Since cotton and wool process dusts are subject to a MEL, equipment should be chosen which reduces exposure to the lowest level reasonably practicable. Users should choose RPE which will theoretically protect at levels of dust several times higher than those expected. Manufactures will state a designed level of protection but these should be regarded as a maximum and may not be achieved in practice. As a guide, it will almost always be reasonably practicable to provide protection to at least 10 x MEL. This can be achieved with FFP2 respirators, P2 filters in orinasal respirators or powered visor respirators.

Maintenance of control measures

34 The performance of all engineering control measures deteriorates over time with wear and physical damage. Where possible they should receive a visual check at least once a week. In addition they should be thoroughly examined and tested at suitable intervals. For LEV plant these intervals should not be more than 14 months. Records should be kept for at least 5 years. Further advice is given in the HSE booklet HS(G) 54 The maintenance and testing of local exhaust ventilation⁷ and in the COSHH General ACOP4.

35 Respiratory protective equipment should be visually inspected by the user each time it is used. Non-disposable equipment should be thoroughly examined, and repaired and tested if needed, at least once every month in accordance with the manufacturer's instructions. Records should be kept. Further information is given in HSE booklet HS(G) 53 Respiratory protective equipment - a practical guide for users⁸.

Information, instruction and training

36 Workers should have sufficient information about cotton and/or wool process dust to know the health risks created by exposure. They should know about the control measures which the company has in place, how to use them and how to report defects.

37 Workers who have to wear RPE should know the limitations of the protection offered. They should know how to visually check the equipment, how to wear it and how to check that it fits. They should know how often to replace filters etc, and how to get the equipment maintained and repaired.

38 Workers responsible for maintenance and repair of any equipment should receive appropriate training.

References

1. Estimating the risks of respiratory symptoms amongst workers in the UK Wool Industry IOM Report TM/97/2 1992, Institute of Occupational Medicine Ltd, Edinburgh.
2. General methods for sampling and gravimetric analysis of respirable and total inhalable dust MDHS 14/2 HSE Books 1997 ISBN 0 7176 1295
3. Occupational Exposure Limits GN EH 40 (published annually) HSE Books ISBN 0 7176 1474 3 (for EH40/98).
4. General COSHH ACOP and Carcinogens ACOP and Biological Agents ACOP: Control of Substances Hazardous to Health Regulations 1994 L5 HSE Books 1997 ISBN 0 7176 1308 9.
5. The dust lamp: A simple tool for observing the presence of airborne particles MDHS 82 HSE Books 1997 ISBN 0 7176 1362 3.
6. BS 5415 Part 2 Section 2.2: Supplement No 1 1986 (1993): Specification for Type H - industrial vacuum cleaners for dusts hazardous to health.
7. The maintenance, examination and testing of local exhaust ventilation HS(G)54 HSE Books 1990 ISBN 0 11 885438 0. Back to reference of footnote 7
8. Respiratory protective equipment: a practical guide for users HS(G)53 HSE Books 1990 ISBN 0 7176 1198 1 (currently under revision). May 1998. Back to reference of footnote 8

The following guidance is considered good practice (rather than compulsory) but you may find it useful in deciding what you need to do to comply with the law.  However, the guidance may not be directly applicable in all circumstances and any queries should be directed to the appropriate enforcing authority.

The advice here is on the control of process dusts in cotton and wool textile mills. The diseases caused by the two dusts are different and the industries have separate historical roots and traditional processes.  However, many of the processes and sources of dust are similar enough to be discussed together and the control solutions may be similar in many cases. Where there are significant differences they are discussed separately.

Cotton and flax dusts

An inventory of fibres to classify their potential hazard and risk