Oxford Handbook of Occupational Health (2 edn)
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Exposure prevention and control
Prevention and control
As far as exposure to hazardous substances is concerned, there is a legal duty under the COSHH Regulations to prevent or, where this is not reasonably practicable, to control exposure adequately.
Where it is not reasonably practicable to prevent exposure, the employer must apply protection measures appropriate to the activity including, in order of priority:
design and use of appropriate work processes, systems of work, engineering controls, and the provision of suitable work equipment and materials
the control of exposure at source including use of ventilation systems and appropriate organizational measures to minimize the risks
where adequate control of exposure cannot be achieved then suitable PPE should be used in addition to measures listed here.
The measures used to control exposure should include:
arrangements for safe handling, storage, transport and disposal (waste materials) of substances hazardous to health
suitable maintenance procedures
reducing the number of employees exposed, the level and duration of exposure, and the quantity of material used
general ventilation
appropriate hygiene measures including adequate washing facilities.
Exposure to carcinogens
Where exposure to carcinogens cannot be prevented, the following control measures are required in addition to those described here.
Total enclosure of process and handling systems
Prohibition of eating, drinking, and smoking
Cleaning floors, walls, and other surfaces at regular intervals
Designating those areas and equipment which may be contaminated
Storing, handling, and disposing of carcinogens safely, including use of closed and clearly labelled containers.
Personal protective equipment
PPE provided by the employer should be suitable for the purpose and comply with the Personal Protective Equipment Regulations 2002
PPE including protective clothing should be properly stored in a well-defined area, checked at suitable intervals, and, if defective, repaired or replaced.
Use of controls
Every employer who provides control measures is required to take reasonable steps to ensure that they are properly used
Employees must make full and proper use of any control measures provided and report defects to their employer.
Maintenance, examination, and testing of controls
Employers are required to maintain plant, equipment, engineering controls, and PPE in an efficient state, in efficient working order, and in clean condition
All control measures including systems of work and supervision should be reviewed
All LEV should be examined and tested every 14mths unless another interval is specified, e.g. in Schedule 4 of the COSHH Regulations
Where RPE (other than disposable RPE) is used to control exposure the employer should ensure that it is examined and, where appropriate, tested at suitable intervals.
Principles of good practice
In the UK a set of principles of good control practice are used as a basis for judging whether control is adequate for hazardous substances. These include:
Design and operate processes and activities to minimize emission and the spread of agents
Take in to account all relevant routes of exposure when developing control measures
Control exposure by means that are proportional to health risk
Choose the most effective and reliable control options that minimize the emission and spread of health hazards
Where adequate control cannot be achieved by other means, provide suitable PPE, in combination with other control measures
Check and review regularly all aspects of control measures for their continuing effectiveness
Inform and train employees about the hazards and risks from the agents with which they work and the use of control measures developed to minimize risks
Ensure that the introduction of any control measures does not increase the overall risk to health and safety.
Control hierarchy: source, transmission, and the individual
When controlling exposure to pollutants, the objective is to ensure that safe levels are achieved. The following three components should be considered in turn: (1) control at source; (2) prevent or control transmission of the pollutant to the individual; (3) protect the worker.
(1) Control at source
Eliminate the hazard by:
changing the process or method of work so that the hazard is not created
substitute hazardous with non-hazardous substances
Modify the process to reduce the frequency, intensity or duration of emission
Substitute substance with one of lower toxicity or different form of the same substance
Enclose the process/sources of emission
Provide extraction ventilation
Improve process/equipment maintenance
Limit areas of contamination, e.g. spills, leaks.
Use alternative tools (altered frequency and amplitude)
Introduce or increase damping; isolate machine from floor (noise)
Avoid/cushion impact.
(2) Prevent/control transmission
Shielding between the worker and source
Increase distance
Housekeeping
Sufficient dilution ventilation.
Reflective and absorbent barriers
Active noise control.
(3) Individual
Automatic or remote control
Enclose the worker
Safer work practice and systems of work
Education, training, supervision
Provide PPE
Reduce exposure time
Reduce number of workers exposed
Health surveillance.
Software/organizational solutions
Options for controlling exposure to hazards in the workplace can be categorized broadly as software (management solutions) and hardware (engineering) methods. Selection and use of PPE is discussed on 
pp.
652–66.
Hierarchy of software/organizational solutions
Elimination
Complete elimination of processes or substances is usually difficult. Elimination is usually limited to unnecessary operations or poor work practices. In some cases high-risk activities are subcontracted to another operator.
Substitution
By a less toxic substance: e.g. in painting using water-based solvents or organic solvents of lower vapour pressure
By the same substance: but in a form that reduces exposure, e.g. use material in pellet form rather than as a powder.
Designing or redesigning the process
Reductions in exposure may be achieved by adjustments to the way the job is performed or modifying the layout of the process and the operator’s work procedures. For example, Fig. 32.1 shows alternative methods for drum filling.
Alternative methods of drum filling. (Reproduced from Sadhra SS, Rampal KG (1999). Occupational health-risk assessment and management.)
Suppression of the substance
Suppression can be achieved in a number of ways. For example, water is used as dust suppressant. Evaporation of vapour from volatile solvents in tanks can be suppressed by using a refrigerated strip just above the surface, creating a cool layer of concentrated vapour and reducing further evaporation. In electroplating the surfaces of tanks can be covered by floating plastic spheres, which reduce the surface area available for evaporation, or by adding low-density liquid surfactants.
Other software methods
Good work practice and systems (including good housekeeping)
Appropriate supervision
Job rotation
Information, instruction, and training: the worker must be made aware of the following:
hazards to which they are exposed, and the risks to health
factors (process, equipment, method of work, environment) which may affect their exposure
any relevant occupational exposure limits
significant findings of risk assessments
appropriate precautions and actions to be taken in order to safeguard health
the correct use of control measures provided and how to recognize and report defects, e.g. PPE, engineering controls
the signs and symptoms associated with the hazards and reporting requirements.
Hardware/engineering solutions
Engineering controls are often not well designed or well maintained and rely on the operator to use them correctly. The hierarchy of control is:
Total enclosure under negative pressure
Partial enclosure with extraction
General dilution ventilation (see p.
642).
Total enclosure under negative pressure
To reduce exposure to very toxic substances the contaminants are handled in an enclosure under negative pressure, e.g. hot cells for radio-active materials, glove boxes, and bead blasting cabinets.
Partial enclosure with extraction
Extraction booths
The source of emission is enclosed on all sides, except where access is needed (Fig. 32.2(a)). Examples include chemical fume cupboards and paint spray booths. Air velocity at the opening (face velocity) should be sufficient to prevent escape of substance in to the environment. Typical face velocities for booths are in the range 0.5–2.5m/s.
Extraction ventilation devices: (a) extraction booths. (b) Canopy hoods. (c) Open-face hood.
Canopies
Canopies (Fig. 32.2(b)) are designed to draw upwards, and thus are best designed to capture pollutants from hot processes, but are unsuitable if the worker needs to lean over the process.
Hoods
Hoods are placed at the side or behind the source in relation to the worker (Fig. 32.2(c)). Typical capture velocities for pollutants range from 0.25 to 10m/s.
For hoods, the velocity decays rapidly with distance from the hood, e.g. for a circular hood the velocity is only approximately 10% of the face velocity one diameter away. For this reason, the process should be conducted close to the hood, i.e. within the capture distance
Once captured, pollutants need to be kept airborne in the ducting, which is achieved by minimum transport velocities. Transport velocities range from 7 to 10m/s for fumes to >20m/s for heavy and moist dust, e.g. paint-spraying particles
Hoods with width to length ratios <0.2 are called slots. Slots are commonly used on degreasing tanks, cleaning baths, and electroplating tanks to remove vapours and mists released from the tank surfaces.
High velocity, low volume (HVLV)
1 HVLV extraction is used to draw particles directly from the point of release by a nozzle handling high air velocities. The chosen velocity must be higher than the tip speed of the tool, e.g. cutting, grinding, sanding.
General (dilution) ventilation
General (or dilution) ventilation reduces the concentration of the contaminant by mixing the contaminated air with clean, uncontaminated air. Air is supplied to and from an area or building via air exhaust fans placed in the walls or roof of a room or building. The air supply may also be filtered and heated.
General ventilation requirements are covered in the Workplace (Health, Safety and Welfare) Regulations 1992:
Fresh air is required to provide oxygen, remove carbon dioxide, remove excess heat or, if conditioned, provide heat, remove odours, and dilute contaminants arising from workplace activities
Air introduced into workplaces should be free of contaminants such as engine exhaust emissions or discharges from nearby extract outlets
Air may be re-circulated to conserve energy costs. Re-circulated air, including air conditioning systems, should be filtered to remove impurities and have fresh air added to it before being reintroduced to the workplace
Mechanical ventilation systems should be regularly cleaned and tested to ensure that they are kept clean from anything that may contaminate the air
Insufficient air changes may lead to tiredness, lethargy, dry or itchy skin, and eye irritation
CIBSE produces recommended fresh air supply rates per person (CIBSE Guide A: Environmental Design). The fresh air supply rate should not normally fall below 5–8L/s/occupant
HSE has published detailed guidance on measures to avoid Legionnaires’ disease caused by Legionella pneumophila which grows in water-cooling towers.1
Use of general ventilation to control exposure to hazardous substances
General ventilation is used to complement LEV systems in industrial environments. Occasionally, when the installation of LEV is impractical, e.g. in confined space, exposure reduction may be achieved by dilution ventilation. The aim is to dilute a pollutant to a safe level before it reaches the breathing zone of the worker.
When used to control chemical pollutants, dilution ventilation is limited to situations where the pollutants;
Are produced (released) at a low concentration and uniform rate
Are of relatively low toxicity
Not drawn or blown towards the worker(s).
When designing dilution ventilation systems consideration needs to be given to the location of air inlet, position of source of the pollutant and the position of the worker. Dilution ventilation is more effective if the exhaust fan is located close to exposed worker and the air supply (makeup air) is located behind the worker so that contaminated air is drawn away from the worker’s breathing zone (Fig 32.3).
Example of good (a) and poor dilution (b) ventilation design.
Factors affecting performance of ventilation systems
LEV systems comprise a hood, enclosure, or slot (negatively pressurized to ensure an inward current of air) connected to a fan via ducting with an air-cleaning device to ensure that the discharged air is fit for recirculation or emission. Fig. 32.4 shows components of an LEV system.
Components of LEV system. © HSE (1998). Maintenance, examination and testing of local exhaust ventilation, HSG54, figure 1, p. 2. HSE Books, Sudbury.
Factors leading to poor performance
LEV performance depends on its design, the integrity of its components and its maintenance and use. Inadequate performance results from:
Insufficient enclosure
Low capture velocity
Extracted air volume is lower than the volume of pollutant released
Filters and air cleaners blocked
Restricted, blocked, or damaged ducting
Ducting too resistant
Fan of the wrong type or size
Fan entry conditions unsatisfactory: bend or damper close to fan inlet affecting velocity profile
Fans badly installed: the wrong way round or rotating in the wrong direction
Fan blades dirty or corroded, or motor seized
Air discharge to atmosphere affected by wind: best to discharge vertically. Weather shields must not restrict the airflow from the discharge point
No provision to allow make-up air to replace that extracted
Multi-branched system not balanced
Poor maintenance and care
New workstation added without adjusting fan performance.
LEV system components
Inlets: such as booths, hood, slot, canopy, or enclosure
Ducting: which may contain bends, junctions, dampers; it may be circular or rectangular in cross section and rigid or flexible
Fans: usually centrifugal type
Air cleaners: such as bag filter, wet scrubber, cyclone, or solvent recovery device
Discharge: to atmosphere via a stack, diffuser, grille, or just open duct.
Local exhaust ventilation: assessing performance
Examination and testing
According to HSG258 (2011) examination and testing of LEV involves three stages:
A through visual examination to verify the LEV is in efficient working order, in good repair, and in a clean condition
Measurement and examination of the technical performance of the system against its specification, i.e. comparison with original commissioning report
Assessment to check the control of worker exposure is adequate.
Visual and structural examination
External examination of all parts of the systems for damage, wear and tear
Check filter cleaning devices (e.g. mechanical shake down system) are working correctly
Check pressure (built in) gauges, e.g. located before and after filter
Check that the monitors and alert/alarms are working correctly
Check for deposits of settled dust in and around the LEV hood.
Assessment of the technical performance
Static pressure measurements taken behind each hood, and across the filter and the fan
Check velocities (capture, face and transport) of air at various points in the systems (as specified in the system commissioning manual)
Calculate the airflow rates (q) at the face of the hood or booth and in the duct including at the filter and fan:
Q = v × a,
where v is the velocity (m/s), a is the cross-section area of hood or duct (m2)
Check speed of fan and motor
Check the replacement or make-up air supply
Test the air cleaner performance and any air re-circulating systems.-
Compare the result of testing with the design specification for the system.
The assessment of control effectiveness
Ensure operator’s working zone is within capture zone of the LEV (Fig. 32.5)
Dust lamp tests to check escape of fine dust or mists
Smoke tube or leak tests
Observe the operator and work practice
Conduct air sampling to determine whether control is achieved.
Capture and working zone. Note: The capture zone is the space in front of the hood where the air velocity is sufficient to capture the contaminant. The working zone is defined as the space where the activity generates the contaminant. For effective control, the working zone must be lie within the capture zone of the hood.
Definitions
Capture velocity: the air velocity required at the source of emission sufficient to cause the pollutant to move towards the mouth of the extractor and thus be successfully captured
Face velocity: the air velocity at the opening of a hood or enclosure
Transport velocity: minimum velocity required in the system, including ductwork and extract devices, to keep collected particles airborne and to prevent them from being deposited in the system
Static pressure: the pressure exerted by a fluid in motion at right angles to the direction of flow
Velocity pressure: the pressure equivalent of the kinetic energy of a fluid in motion. It is calculated from the expression Pv = 0.5pv2 where p is the density of air (kg/m3) and v is the velocity of air (m/s).
Total pressure: the sum of the static and velocity pressures at a point in an air stream. It can be +ve or –ve relative to atmospheric pressure.
Further information and guidance
HSE (2011). Controlling airborne contaminants at
work—a guide to local exhaust ventilation (LEV), HSG258. HSE, Sudbury. Available at: 
http://www.hse.gov.uk/pubns/priced/hsg258.pdf
HSE (2008). Clearing the air—a simple guide to buying and using
local exhaust ventilation (LEV), INDG408. HSE, Sudbury. Available at: http://www.hse.gov.uk/pubns/indg408.pdf
Recording the examination and testing of local exhaust ventilation plant
The name and address of the employer
The identification (and location) of the LEV, and the process and substances concerned
The dates of the examination and test
The process conditions at the time of test, e.g. normal
Diagram of the LEV system showing position of hood, filter, fan and test points
Information about the LEV plant which shows:
its intended operation performance for controlling adequately
exposure to hazardous substances
whether the LEV is still achieving the same performance
if not, the adjustment or repairs needed to achieve that performance
Methods used to make the judgment of performance
Results of any air sampling relevant to LEV performance
Name, job title, and employer of the person carrying out the examination and test
Observation on the way the operator used the LEV
Signature of person carrying out the test.
The employer should have a LEV ‘user manual’ and a system ‘logbook’
These documents should be supplied as part of the design, installation, and commissioning process
The maximum time between tests for most LEV systems is 14mths (see p.
532, Control of Substances Hazardous to Health Regulations Regulations 2002)
The employer should keep the examination and test report for at least 5yrs.
Personal protective equipment: legal requirements and use
Definition
PPE is defined as all equipment (including clothing) that is intended to be worn or held by a person at work, and which protects him/her against one or more risks to his health or safety.
Legal requirements
See PPE at Work Regulations 1992 (as amended) Personal protective equipment: legal requirements and use, PPE at Work Regulations 1992. The law governing the use of PPE in other specific regulations is contained in:
PPE at Work Regulations 1992 COSHH 2002 (as amended)
Control of Asbestos at Work Regulations 2002 (as amended)
Control of Lead at Work Regulations 2002
Ionizing Radiation at Work Regulations 1999
Confined Spaces Regulations 1997
Control of Noise at Work Regulations 2005
Construction (Head Protection) Regulations 1989.
1 PPE is considered as the last resort to protect against risks to health and safety. Thus there is a need to demonstrate first that the risk cannot be controlled adequately by other means.
Use of PPE
Effective protection is only achieved by suitable PPE, correctly fitted and maintained, and properly used
PPE is used widely, but should be considered as the last resort as:
it only reduces exposure for the individual wearer, whereas control at source protects all those in the area
the actual level of protection is difficult to assess
it may interfere with work tasks/practice
it may be uncomfortable and restrict the wearer, limiting movement, and visibility.
PPE should be selected and used after justification for its use has been made in the risk assessment. For example RPE can be used in the following situations:
where inhalation exposure remains despite use of other controls, i.e. used minimize residual risk
where there is short-term or infrequent exposure and use of other controls is not practical
as an interim measure, e.g. when putting in place other controls
for emergency response, e.g. safe exit or emergency rescue
for emergency work/when there is temporary failure of controls.
Setting up a effective PPE programme
Having assessed the risk and implemented all reasonable control measures, the following steps should be considered when setting up a PPE programme.
Identify individuals/tasks/environment where PPE is needed
Select appropriate PPE to control residual exposure
Involve worker in the PPE selection process
Match PPE to each individual wearer
Carry out fit tests for respiratory protective equipment (RPE)
Ensure the use of PPE does not create additional risks
Ensure that the PPE is compatible with other PPE
Minimize PPE use time by defining when it should be used, e.g. particular tasks
Train the wearer in the correct use of their PPE and supervise use
Inspect PPE to ensure it is correctly maintained
Provide suitable storage facilities to prevent contamination
Record: PPE issue, maintenance, inspection, and RPE fit-testing data
Inform individuals of the need for PPE, consequences of PPE failure and the importance of reporting PPE defects.
Selecting respiratory equipment
The decision to use RPE should be justified in a risk assessment. When selecting RPE consideration must be given to:
Individual factors: health status, e.g. cardiorespiratory problems
Contaminant: form of substance, single substance/mixture, nature of release (energy), concentration and variation, toxicity, OEL
Task: duration, other PPE used, mobility, manual dexterity, visibility, communication, work rate (metabolic rate)
Environment: indoor/outdoor, temperature, humidity
Legal requirements: CE marking, employer and employee duties
Costs: equipment, training, testing, repair/replacing storage, and record keeping.
RPE protection factors
The effectiveness of RPE is indicated by the assigned protection factor (APF). The APF is the level of respiratory protection that the respirator (or class of respirators) is expected to provide to employees when it is used correctly.
Example: A respirator with an APF of 10 should reduce the workers exposure by a factor of 10, i.e. to one-tenth of exposure level in the breathing zone (outside the mask). Therefore the maximum use concentration (MUC) an employee can be expected to be protected when wearing this respirator is 10 times the WEL.
1 Whenever the exposure approaches the MUC, then the next higher class of respirator should be selected.
APF values assigned to different types of RPE are given in HSG 53 (HSE, 2005). Examples of RPE are shown on p. 655, Protective equipment.
Types of respirator.
Required protection factor
Example: A worker is exposed to dust assigned a WEL 8h TWA = 5mg/m3. The daily TWA exposure is measured to be 20mg/m3. In order to reduce the personal exposure to the WEL, the required protection (PF) is: PF= 20/5 =4.
RPE selector guide
HSG 33 (HSE, 2005) describes a generic guide on the selection of RPE which comprises 5 steps:
Step1: details about the company and the work environment
Step 2: information on control measures currently in use (other than RPE), reasons for wanting to use RPE, whether work is to be carried out in a confined space, and risk of oxygen deficiency
Step3: determination of the health hazard group (HHG) for the substance and the level of protection needed. The HHG is based on risk phrases assigned to the substance. The required PF is determined from the combination of HHG and the amount of substance used and its dustiness/volatility
Step 4: consideration of tasks and individual factors that may affect the selection of the RPE, e.g. work rate, mobility, medical conditions
Step 5: consider need to test the selected RPE for a good fit over the mouth and nose (fit test).
RPE fit testing
A major cause of leaks for RPE equipment is poor fit. Fit testing will ensure that the RPE selected is suitable to the individual wearer.
Tight-fitting RPE must be fit tested as part of the initial selection stage
The fit-test report should include the following:
name of the person fit tested
make, model, type, and size of face-piece tested
exercises performed during the test
the test method (qualitative or quantitative)
measured fit factor if applicable
date of test
details of person carrying out the test
Fit testing should be conducted by a competent person. Competence can be demonstrated through achieving accreditation under the ‘Fit2Fit RPE Fit Test Providers Accreditation Scheme’ developed by the British Safety Industry Federation (BSIF). For further details on the scheme, see http://www.fit2fit.org.
Further information
HSE (2005). Respiratory protective equipment at work.
a practical guide, HSG 53. HSE Books, Sudbury. Available at: http://books.hse.gov.uk/hse/public/saleproduct.jsf?catalogueCode= 9780717629046
BSI (2005) Respiratory protective devices—recommendations for the selection, use, care and maintenance, guidance document BSEN529. BSI, London.
Types of respiratory protective equipment
RPE can be divided in to two main types:
respirator (filtering device)—i.e. filter used to remove contaminants; do not use for protection in situations with reduced oxygen levels
breathing apparatus (BA)—requiring a supply of breathing quality air from an independent source, e.g. air compressor, air cylinder
Types of breathing apparatus.
Filter for respirators
Particle filters are marked with a ‘P’ sign and filtration efficiency number 1 (low), 2, or 3 (high). If the filter is re-usable with fan-assisted respirators they will also have a sign ‘TH’ or ‘TM’
Gas/vapour filters are categorized by the substance type they can be used against. The filter is marked with a letter indicating type, a number to indicate capacity (1 = low, 2 = medium, 3 = high) and a colour code. See Table 32.2.
| PF required | Respirators | Breathing apparatus | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Half-mask, particle filters | Half-mask, gas filters | Full face mask, particle filters | Full face mask, gas filters | Powered (fan-assisted) masks | Powered (fan-assisted) hoods | Fresh air hose | Constant flow airline BA | Demand valve BA | |
4 | FFP1, FMP1, P1 | P1 | |||||||
10 | FFP2, FMP2, P2 | FF gas, FM gas, Gas | P2 | TM1 | TH1 | LDH1 | |||
20 | FFP3, FMP3, P3 | Gas | TM2 | TH2 | LDH2, LDM1, LDM2, Half-mask | ||||
40 | P3 | TM3 | TH3 | Full face mask, Hood | LDH3, LDM3, Hood, Full mask | ||||
200 | Suit | ||||||||
2000 | Airline, self-contained | ||||||||
From HSE (2005). Respiratory protective equipment at work, HSG 53. HSE Books, Sudbury, p. 30. © Crown copyright, material is reproduced with the permission of the Controller of HMSO and Queen’s Printer for Scotland. | |||||||||
| PF required | Respirators | Breathing apparatus | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Half-mask, particle filters | Half-mask, gas filters | Full face mask, particle filters | Full face mask, gas filters | Powered (fan-assisted) masks | Powered (fan-assisted) hoods | Fresh air hose | Constant flow airline BA | Demand valve BA | |
4 | FFP1, FMP1, P1 | P1 | |||||||
10 | FFP2, FMP2, P2 | FF gas, FM gas, Gas | P2 | TM1 | TH1 | LDH1 | |||
20 | FFP3, FMP3, P3 | Gas | TM2 | TH2 | LDH2, LDM1, LDM2, Half-mask | ||||
40 | P3 | TM3 | TH3 | Full face mask, Hood | LDH3, LDM3, Hood, Full mask | ||||
200 | Suit | ||||||||
2000 | Airline, self-contained | ||||||||
From HSE (2005). Respiratory protective equipment at work, HSG 53. HSE Books, Sudbury, p. 30. © Crown copyright, material is reproduced with the permission of the Controller of HMSO and Queen’s Printer for Scotland. | |||||||||
| Filter type | For use against | Colour code | Other information |
|---|---|---|---|
A | Organic gases and vapours, boiling point >65°C | Brown | EN 14387 |
B | Inorganic gases and vapours | Grey | EN 14387. Do not use against carbon monoxide |
E | SO2 and other acid gases | Yellow | EN 14387 |
K | Ammonia and its organic derivatives | Green | EN 14387 |
Hg | Mercury | Red and white | EN 14387, includes P3 particle filter. Max. use time 50h |
NO | Oxides of nitrogen | Blue and white | EN 14387, includes P3 particle filter. Single use only |
AX | Organic gases and vapours, boiling point <65°C | Brown | EN 14387. Single use only |
SX | Substance as specified by the manufacturer | Violet | EN 14387 |
From HSE (2005). Respiratory protective equipment at work, HSE 53. HSE Books, Sudbury, p. 28. © Crown copyright, material is reproduced with the permission of the Controller of HMSO and Queen’s Printer for Scotland. | |||
| Filter type | For use against | Colour code | Other information |
|---|---|---|---|
A | Organic gases and vapours, boiling point >65°C | Brown | EN 14387 |
B | Inorganic gases and vapours | Grey | EN 14387. Do not use against carbon monoxide |
E | SO2 and other acid gases | Yellow | EN 14387 |
K | Ammonia and its organic derivatives | Green | EN 14387 |
Hg | Mercury | Red and white | EN 14387, includes P3 particle filter. Max. use time 50h |
NO | Oxides of nitrogen | Blue and white | EN 14387, includes P3 particle filter. Single use only |
AX | Organic gases and vapours, boiling point <65°C | Brown | EN 14387. Single use only |
SX | Substance as specified by the manufacturer | Violet | EN 14387 |
From HSE (2005). Respiratory protective equipment at work, HSE 53. HSE Books, Sudbury, p. 28. © Crown copyright, material is reproduced with the permission of the Controller of HMSO and Queen’s Printer for Scotland. | |||
Combined filters are marked for both particles and gas/vapour, e.g. A1P3—organic vapour with capacity class 1 and high efficiency particle filter.
Further information
HSE (2005). Respiratory protective equipment at work: a practical guide, HSG53. HSE Books, Sudbury.
Hearing protectors
Requirements, types, use, and maintenance
Guidance on hearing protection can be found in the CNAWR 2005 ( p.
548, Control of Noise at Work Regulations 2005). More detailed information can be found in BS EN 458:2004 Hearing protectors, Recommendations for selection, use, care and maintenance
Under CNAWR the use of personal hearing protectors (HP) is compulsory for employees whose exposure to noise is likely to reach either of the upper exposure action values, i.e. 85dB(A) and 137dB(B) and for any employees working within areas assigned as hearing protection zones
HP should be used where additional protection is needed above what can be achieved using other methods of noise control (e.g. engineering) and as a short term measure
Avoid HPs that over protect the worker, i.e. reducing the level at the ear below 70dB
HPs must be CE marked showing that it meets the European Standard BS EN 352
HPs include earmuffs and earplugs; the latter can be custom moulded.
Most HPs provide greater protection at higher frequencies than at lower frequencies.
Earmuffs
Easy to fit, re-usable, clearly visible, and hence easy to monitor. They may be uncomfortable in warm conditions. Long hair, beards, jewellery, or glasses may reduce protection. More expensive than ear plugs.
Seals: check seals for cleanliness, hardening, and damage
Cup: check for cracks, holes, damage
Headbands: avoid over-bending and twisting, check tension
Store in a clean environment.
Earplugs
More suitable when used with other PPE, e.g. safety glasses. Workers who suffer from recurrent otitis externa may be unable to tolerate earplugs. Custom-made plugs are more comfortable and are easier to fit for some wearers. However, need to conduct fit tests before putting into use.
Reusable plugs: clean regularly, ensure not damaged or degraded
Issue to individual: not to be shared
Require careful insertion to ensure effective protection
Provide greater protection at higher than low frequency
Risk of infection (dirty hands)
Disposable plugs: use only once.
Special protector types
Level-dependent (or amplitude-sensitive) protectors: designed to protect against noise, but allow communication during quieter periods.
Flat or tailored frequency protectors: these provide similar protection across all frequencies which can assist communication. Useful where it is important to be able to hear high-frequency sound at the correct level relative to lower-frequency sounds, e.g. musicians.
Active noise reduction (ANR) protectors: incorporate an electronic sound-cancelling system enabling additional noise attenuation. Effective at low frequencies (50–500Hz).
Protectors with communication facilities: these use a wire or aerial to rely signals, alarms, and messages to the wearer. The signal level should not be too loud and the microphone should be switched off when not in use.
Selecting hearing protectors
When selecting HPs the following should be considered:
Noise level (personal) and exposure variation
Pattern of exposure
Noise reduction (attenuation) provided by the protector
Work environment (temperature, humidity, dust, dirt)
Compatibility with other PPE worn
Comfort and wearer preference
Hearing needs: communication, hearing warning sounds, conducting tasks
Costs: equipment, maintenance, training
Health problems: ear infections, discharge, etc.
Legal requirements.
Further information
BS EN 458:2004 Hearing Protectors. Recommendations for Selection, Use, Care and Maintenance. Guidance Documents.
Predicting noise reduction
The noise level at the ear (L’A) when hearing protection is worn can be estimated using three different methods (octave band method, high, medium, and low frequencies (HML) method, and single rating number (SNR) method). L’A is estimated by subtracting the estimated noise reduction (using manufacturer’s performance data) from measured noise data.
Manufacturers’ hearing protection data
The supplier must provide the following information for the HP. An example of supplier data is shown in Table 32.3:
Mean and standard deviation attenuation values at each octave band centre frequency (63Hz–8KHz)
Assumed protection values (APrV) at each frequency, i.e. mean protection minus one SD
H, M, L and SNR values.
| Octave band centre frequency (Hz) | ||||||||
|---|---|---|---|---|---|---|---|---|
| 63 | 125 | 250 | 500 | 1000 | 2000 | 4000 | 8000 | |
Mean attenuation | 17.3 | 21 | 24.5 | 27.3 | 27.9 | 33.8 | 36.1 | 40.8 |
Standard deviation (dB) | 5.4 | 5.3 | 6.7 | 6.6 | 4.8 | 3.7 | 5.2 | 6.5 |
Assumed Protection Value (APV) | 11.9 | 15.7 | 17.8 | 20.7 | 23.1 | 30.1 | 30.9 | 34.3 |
Single number values | H | 29 | M | 23 | L | 20 | SNR | 27 |
APV, mean attenuation minus 1 SD. | ||||||||
| Octave band centre frequency (Hz) | ||||||||
|---|---|---|---|---|---|---|---|---|
| 63 | 125 | 250 | 500 | 1000 | 2000 | 4000 | 8000 | |
Mean attenuation | 17.3 | 21 | 24.5 | 27.3 | 27.9 | 33.8 | 36.1 | 40.8 |
Standard deviation (dB) | 5.4 | 5.3 | 6.7 | 6.6 | 4.8 | 3.7 | 5.2 | 6.5 |
Assumed Protection Value (APV) | 11.9 | 15.7 | 17.8 | 20.7 | 23.1 | 30.1 | 30.9 | 34.3 |
Single number values | H | 29 | M | 23 | L | 20 | SNR | 27 |
APV, mean attenuation minus 1 SD. | ||||||||
Noise level data required for estimating protection
The following types of noise data should be measured depending on the method chosen (one of three) to calculate the attenuation afforded by the ear protector.
Octave band analysis: requires measurement of noise level at each octave centre frequency for the range 63Hz–8kHz
HML require measurement of the A-weighted (LA) and C-weighted (LC) sound pressure levels
SNR: requires single measurement of LC only.
Predicting attenuation using the HSE electronic spreadsheet
The measured noise levels and manufacturer’s data can be entered into an electronic spreadsheet to calculate the attenuation afforded by the chosen ear protector. The spreadsheet is available on the HSE website ( http://www.hse.gov.uk/noise). Of the three methods, the octave band analysis method provides the best estimate for L’A.
Hearing protectors usually give lower protection than predicted by manufactures data due to, e.g. poor fitting. The difference between manufacturers’ data and ‘real-world data’ is accounted for in the HSE calculator by ‘derating’ the protection by 4dB.
Protector use time
If HP is removed in a noisy area, even for short period, amount of protec tion provided will be reduced (Fig. 32.8).
Effectiveness of hearing protectors in relation to time worn. Protectors providing (A) 30dB attenuation, (B) 20dB attenuation, and (C) 10dB attenuation. From HSE (2005). The Control of Noise at Work Regulations 2005. HSE Books, Sudbury. Material reproduced with permission from the Controller of HMSO,
Information for employees
Employees should be provided with information on HPs including:
Why and where HPs need to be worn?
How replacements can be obtained?
How to wear HPs with other personal protection?
How to check, store, and report damage to HPs?
Gloves
Glove selection and use
Gloves differ in design, material, thickness, and size. The following factors should be considered when selecting gloves to avoid contact with harmful substances:
Type and duration of dermal contact
The user: size (use sizing charts) and comfort.
The tasks: e.g. manual dexterity requirements, need for sterile gloves
Work environment (temperature and humidity).
| Protection against | Glove type (examples) |
|---|---|
Penetration and abrasion | Leather, Kevlar |
Thermal | Terrycloth (protect against heat and cold) Neoprene (handling oils at low temperature) |
Fire | Chromated leather gloves |
Chemical protection | Neoprene, natural rubber, nitrile, butyl, PVA, PVC, Vitron |
| Protection against | Glove type (examples) |
|---|---|
Penetration and abrasion | Leather, Kevlar |
Thermal | Terrycloth (protect against heat and cold) Neoprene (handling oils at low temperature) |
Fire | Chromated leather gloves |
Chemical protection | Neoprene, natural rubber, nitrile, butyl, PVA, PVC, Vitron |
| Glove type | Protection against | Limitations |
|---|---|---|
Nitrile (synthetic rubber) | Oil-based chemicals, lubricants, aliphatic solvents and aqueous chemicals | Prone to swelling with some solvents |
PVC | Aqueous chemicals, e.g. acids and alkalis | Protection for some solvents limited because of plasticizers |
Neoprene | Petrol, oil, lubricants | |
PVA | Most organic solvents | Soluble in water |
Butyl | Strong acids | Poor resistance to oils and lubricants |
Viton | Chlorinated solvents and aromatic hydrocarbons | Poor resistance to ketones |
Latex | Aqueous chemicals | Powdered gloves may cause allergic reactions and sensitization |
| Glove type | Protection against | Limitations |
|---|---|---|
Nitrile (synthetic rubber) | Oil-based chemicals, lubricants, aliphatic solvents and aqueous chemicals | Prone to swelling with some solvents |
PVC | Aqueous chemicals, e.g. acids and alkalis | Protection for some solvents limited because of plasticizers |
Neoprene | Petrol, oil, lubricants | |
PVA | Most organic solvents | Soluble in water |
Butyl | Strong acids | Poor resistance to oils and lubricants |
Viton | Chlorinated solvents and aromatic hydrocarbons | Poor resistance to ketones |
Latex | Aqueous chemicals | Powdered gloves may cause allergic reactions and sensitization |
Check that correct gloves have been selected using supplier’s performance data, and that the glove user is not allergic to the glove material, e.g. powdered latex gloves.
The HSE glove selection memory aid (from HSG262) is available on web page M http://www.hse.gov.uk/skin/resources/glove-selection.pdf
Glove failure
Protective gloves can fail to protect the wearer from exposure to chemicals in different ways.
Permeation: chemical migrates through glove
Penetration: bulk flow of chemical through seams, pinholes, closures, porous materials, or other imperfections
Degradation: change in physical properties of glove material as a result of exposure to a chemical agent.
The breakthrough time is defined as the time between the initial application of a test chemical to the outside surface of the protective glove and its subsequent presence on the inside of the material.
Glove performance data
Glove suppliers usually provide chemical resistance charts, with glove performance for different chemicals. Performance is rated using the following data:
Breakthrough time: ranges from 1–10 to >480min.
Permeation rate: fast, medium, or slow
Degradation: scale 0–6.
Applications
Protection from cuts and abrasion, handling sharps
Keeping hands warm in cold weather when using machines that cause HAVS
Handling chemicals, radio-active materials, hot or cold materials
Danger of electrical hazards
Work involving naked flame, welding.
Gloves should be checked regularly and replaced if they are worn or have deteriorated. Workers should receive training in the correct way to care for, put on, wear, and take off gloves. Need to also ensure that there are adequate facilities for storage, cleaning, replacement, and disposal of gloves.
Further information
HSE (2009). Managing skin exposure risk at work, HSG262. HSE Books, Sudbury. Available at: http://www.hse.gov.uk/pubns/priced/hsg262.pdf
Protective clothing
Protective clothing includes separates (jacket, trousers), aprons, overalls, coveralls, and body suits.
Applications
Chemical work protecting against accidental spillages: use aprons
Contact with sprays or jets of chemicals: use coveralls
Wet working: using water sprays for cleaning, use rubbers, plastic, water-repellent coatings, waterproofs, breathable fabrics
Radiant heat from welding, foundries: flame-retardant, insulating, and heat-resistant fabric
Electrical and electrostatic hazards: materials which resist build-up of static electricity.
Precautions
When selecting protective clothing consider the chemical resistance and protection, protection against mixtures, and breakthrough times recommended by the manufacturer
Store used/contaminated clothing separate from clean clothing
Inspect for wear and tear/loose seams and damage
Do not wear loose protective clothing close to moving machines
Clean clothing following the manufacturer’s instructions.
1 If protective gloves or clothes are worn incorrectly this may increase the risk to the individual.
Contaminant may get inside the protective device (glove) and be occluded, resulting in higher exposure
Prolonged use may cause moisture (sweat) on skin which can act as an irritant
Reduces heat loss, which may increase likelihood of heat stress
Latex gloves may cause an allergic reaction in susceptible individuals ( p.
202, Latex allergy)
Gloves worn near moving equipment and machinery parts may be caught in the equipment, drawing the worker’s hand into the moving machinery.
Further information
HSE (1992). Personal protective equipment at work regulations 1992 (as amended). HSE Books, Sudbury.
HSE (1992). A short guide to personal protective equipment at work
regulations 1992. HSE, Sudbury. Available at: http://www.hse.gov.uk/pubns/indg174.pdf
Eye and face protection
Types of eye and face protection
Eye protection can be divided into three basic types:
Safety spectacles: separate lenses in metal or plastic frame with side shields
Goggles: flexible plastic frame with one or two lenses and flexible headband. With the rim in contact with the face, goggles provide eye protection from all sides
Face shields or visors: one large lens with a frame and adjustable head harness or mounted on helmet. Can be worn with prescription lenses. Protects the face, but eyes are not fully enclosed.
Applications
Eye protection is required for the following hazards:
Splashes of chemicals, e.g. acids or body fluids
Chipping and debris from use of power-driven tools on metals, woods, etc.
Molten metal, radiant heat sparks, or hot liquid splashes from furnaces
Intense light (lasers) and other optical radiation likely to cause risks to the eye, e.g. UV light from welding.
Selecting eye and face protection
Table 32.6 shows examples of eye protection for different hazard types.
| Hazard | Eye protection equipment | Examples |
|---|---|---|
Impact | Spectacles with toughened lenses/side screens | Flying swarf Chiselling |
Dust | Goggles Air-fed positive pressure hood with visor | Grinding Shot-blasting |
Molten metal | Goggles Face shield or visor | Casting and pouring |
Radiation (non-ionizing) | Goggles, tinted Face shield or visor with correct protective shade Sunglasses | Welding and lasers (UV radiation) Casting and pouring molten metal/glass (IR radiation) Outdoor work (UV radiation) |
Chemical or biological | Goggles Face shield or visor | Exposure to gases, vapours, liquids, dusts, biological agents |
| Hazard | Eye protection equipment | Examples |
|---|---|---|
Impact | Spectacles with toughened lenses/side screens | Flying swarf Chiselling |
Dust | Goggles Air-fed positive pressure hood with visor | Grinding Shot-blasting |
Molten metal | Goggles Face shield or visor | Casting and pouring |
Radiation (non-ionizing) | Goggles, tinted Face shield or visor with correct protective shade Sunglasses | Welding and lasers (UV radiation) Casting and pouring molten metal/glass (IR radiation) Outdoor work (UV radiation) |
Chemical or biological | Goggles Face shield or visor | Exposure to gases, vapours, liquids, dusts, biological agents |
Precautions
Issue eye protection on a personal basis and ensure that it fits properly
Stored in a protective case
When cleaning, follow manufacturer’s instructions
Do not use when the visibility (scratched and worn lenses) is reduced or the headband is damaged or worn
Lens may mist: use anti-mist sprays or ventilation eye protection.
Standards for selection, use and maintenance
BS 7028: 1999 Eye Protection for Industrial and Other Uses. Guidance on Selection, Use and Maintenance.
Further information and guidance
HSE (2009). European standards and markings for eye
and face protection, OM 2009/3. Available at: http://www.hse.gov.uk/foi/internalops/fod/om/2009/03app3.pdf
British Standards on eye protection. Available at: http://www.bsigroup.co.uk/DualSearch/?q=eye+protection
