B6 Flashcards
Jan 20 See Jan 13 below
Sound Pressure Level : 91dB(C)
Single number rating (SNR) for selected hearing protection (29)
(a) Demonstrate that a realistic estimate of the A-weighted sound pressure level entering the ear of the operators wearing this hearing protection is 66 dB(A). (4)
(b) Explain if the attenuation provided by this hearing protection is appropriate. (2)
Two other methods of calculating hearing protection attenuation are HML and Octave band analysis.
(c) For EACH of these methods, outline the data required to be able to calculate these attenuations for hearing protection. (6)
(d) Other than noise attenuation, outline other factors the employer should consider when selecting hearing protection. (8)
(a) Exposure dB(A) = dB(C) – SNR
dB(A) = 91 – 29 =62
Correcting this number by +4 dB to account for “real world” factors makes 66 dB(A)
(b) With a lower daily exposure action value of 80 dB(A) and the guideline value that permanent exposure to levels up to 70 dB(A)is unlikely to cause hearing impairment - it is therefore likely that it is over protecting the worker’s hearing (since 66 dB(A) is less than half of 70 dB(A))
This hearing protection is therefore not suitable as the worker may not be able to hear warning sounds/alarms in the workplace.
(c) HML method requires knowledge A- weighted and C-weighted average sound pressures Octave band analysis requires knowledge of the sound levels for the full spectrum range of frequencies and the corresponding A-weighting correction for each frequency range/measured in Hertz/Hz
(d) Other factors to consider include:
• The existing noise level without protection
• Compatibility with other personal protective equipment or glasses or facial hair
• Comfort whilst wearing
• Does wearing the hearing protection increase the overall level of risk or add new risks?
• Does the wearer have any health issues that may present problems whilst wearing it?
• How easy it is to adjust to fit the individual worker?
• Whether it is likely to make the wearer too hot
• Whether the wearer is able to carry out the demands of their job whilst wearing it
• Whether workers can communicate sufficiently whilst using the hearing protection
• Whether wearers are able to hear warning sounds or alarms
• Level of training and instruction necessary to use PPE correctly
• Ease of Storage/maintenance/cleaning – care needed to keep equipment effective
• Cost of the hearing protection and how often it will need replacing
• Are there any other barriers to wearing?
− Is it too heavy?
− Does it look ridiculous?
Jan 20
Hand-arm vibration syndrome (HAVS) can be caused by frequent and prolonged use of hand-held power tools.
(a) Identify symptoms of HAVS. (2)
(b) Outline control measures that could help reduce the risk of employees developing HAVS when using hand- held power tools. (8)
(a) Symptoms of HAV’s include: MANC
Muscular - loss of dexterity and grip; • Articular – bone and joint problems; • Neurological – numbness and tingling; • Circulatory – blanching (vibration white finger); • Pins and needles, • Pain in the hands and wrists, • Coldness in hands • Reduced dexterity and sensitivity in the hands,
(b) Control measures include:
Eliminate
• consideration of alternative work methods;
• Outsource – sub-contract;
• Automate the work;
• Use jigs/ or suspension systems to grip heavy tools to minimise loads on hand, wrists and
arms;
Purchasing policy
• avoiding tools that are too small and not powerful enough as these prolong the task;
• replacing the equipment with a lower vibration model;
Maintenance
• replace worn parts and balance;
Time exposed
• plan work;
• job rotation and rest breaks;
I, I & T
• risks, conditions and controls – refresher, TBT;
PPE
• Anti-vibration gloves;
• warm clothing – stimulate circulation in hands;
Organisation control measures
• Refer those experiencing early symptoms to Occupational Health;
• Health surveillance programme;
Jul 19
Similar to Jan 12 Jul 09 Jan 06 Jul 05
Audiometry can be used to assess an employee’s hearing.
(a) Explain what is meant by the term ‘threshold shift’. (2)
(b) The figure below shows an audiogram for an adult employee
(i) Give the name of the hearing condition indicated in this audiogram. (1)
(ii) Describe the physical changes in the inner ear for an adult employee with this audiogram result. (2)
(iii) Outline the resultant effect on hearing for an adult employee with this audiogram result. (1)
(iv) Outline reasons why audiometry testing may not produce an accurate representation of the effects of workplace noise exposure on an employee’s hearing. (4)
(a) Threshold shift = reduction in a person’s sensitivity to sound often caused by high noise exposures. Can be temporary (TTS) or permanent (PTS = NIHL); TS is measured as the difference between the hearing threshold of a subject under test and that of a healthy young adult with no hearing impairment. TS is measured as “hearing loss” in dB(A).
(b)
(i) The audiogram shows someone with Noise Induced Hearing Loss (NIHL)
(ii) The physical changes include damage in the cochlea where the hair cells are flattened or broken off
(iii) There is a reduction in hearing acuity, particularly at around 4KHz frequency. This generally means
that people have difficulty hearing the spoken word particularly when spoken in raised voice. They
may not hear consonants clearly
(iv) there may be background noise or distraction during the test, or the operator may not be competent to conduct the test. The test subject could be tired and not concentrating, particularly if they have been in a noisy environment just prior to the test. The test result shows all hearing loss, which may or may not be due to occupational exposure.
Jul 19
See also Jul 13 Jul 10 Jan 08 Jan 07 Jan 06
The use of hand-held power tools results in employees being exposed to hand-arm vibration (HAV). Outline what should be considered when conducting a risk assessment for exposure to HAV. (10)
Things to consider:
• Who may be affected (anyone at high risk)
• Existing controls in use (physical and procedural)
• The magnitude of the vibration (measured or from manufacturers’ information.
• Duration and frequency of exposure to vibrating power tools
• Calculation of the dose employees are likely to be exposed to.
• Comparison to exposure limit values and action values.
• Temperature of the working environment
• Age and condition of equipment (maintenance regime)
• Health surveillance
• Any further measures necessary
• Review date for risk assessment
Jan 19 Jul 11 Jul 08
Drivers of earth-moving machinery at a large construction site have reported incidences of back pain which they believe are caused by exposure to whole body vibration.
(a) Outline a range of control measures that could be
used to minimise the risk of the drivers
experiencing back pain caused by exposure to whole body vibration.(7)
(b) Suggest THREE other possible work-related causes of the back pain being experienced by these
drivers. (3)
(a) Vehicle selection (power, stability, suitability for terrain) so as to minimise levels of vibration and
ensure compliance with requirements-
ref to exposure action / limit values; provide designated routes avoiding rough / uneven surfaces where practical; regular road / surface maintenance; ensure padded, spring mounted seat, adjustable for weight / size of driver and with adequate back support; job rotation / breaks / task variation; training / information on hazards / health effects / control measures required - eg speeds / driving style etc; supervision
(b) Poor posture / driving position / badly adjusted seat position; ergonomic issues - poor design /
layout of controls / obstructed visibility resulting in repeated stretching, bending, twisting etc; lifting heavy tools and equipment / attachments; repeated climbing into / jumping out of cab
Comment: answers often not referring to scenario
Jan 17
(a) Summarise the duties of an employer under the Control of Noise at Work Regulations 2005. (4)
(b) Give the meaning of the following terms used in noise control:
(i) transmission; (1)
(ii) damping. (1)
(c)
Outline the legal requirements for a hearing protection zone (HPZ) within a workplace. (4)
(a) Duties of an employer include:
Risk assess when exposure is above any LEP,d – identify short/long term controls and detail in noise conservation programme;
• Between 85 – 87 dB (A) LEP,d mandatory hearing protection zone with signage displayed;
• Cannot expose employees above exposure limit value of 87 dB (A) LEP,d or 140 dB (C) peak
pressure;
• If at the lower exposure value of 80 dB (A) but below the upper of 85 dB (A) hearing
protection should be made available on request;
• PPE only as an interim;
• Provide employees with information, instruction and training;
• Provide health surveillance when above upper exposure value or above lower but employee
is vulnerable (pre-existing, family history);
(b)
(i) transmission is the transfer of sound between materials such as air, walls pipes etc
(ii) damping is a way of reducing the noise radiated from a source. By either applying a “sandwich” layer between two vibrating structures or by use of stiffening ribs to reduce vibration.
(c)
It is an area of the workplace where the personal exposure is above the upper exposure action value or the exposure limit value for peak noise;
• The type of signage required for HPZs (blue roundel with hearing protection pictogram, this signage must comply with the requirements of the Health and Safety (Safety Signs and Signals) Regulations 1996;
• The area must be identifiable in advance and access must be restricted where practicable;
• Can be fixed or mobile, temporary or permanent
Jul 16
(a) Describe how an accelerometer can be used as part of the assessment of an employee’s exposure to hand- arm vibration while using a hand-held power tool. (5)
(b) Sometimes it is not possible to use an accelerometer and it is necessary to estimate an employee’s overall exposure to vibration during the working day.
Outline how this estimation can be made. (5)
a) An accelerometer is a vibration transducer which can be attached to a vibrating tool in order to measure the level of vibration that an employee is exposed to during their work activity. It measures the acceleration caused by the vibration in each of three dimensions X,Y, Z.
It can be attached to the surface or handle that the worker is in contact with.
The measurements are taken over a long enough period of time to ensure that truly representative average readings have been collected.
This is used to calculate a personal daily exposure and compared to the Daily Exposure Action Value of 2.5m/s2 and Daily Exposure Limit Value of 5 m/s2 for HAV’s in order to decide further action or control measures.
A calculation of the personal daily exposure in A(8) can be made using the HSE calculator or
ready reckoner;
(b) If it is not possible to use an accelerometer, then published data on vibration magnitude can be used. This can be obtained
Manufacturer’s vibration magnitude data;
• This data is only an estimate of the real-world situation and actual vibration exposure can be
affected by factors such as the work method, the type of material the tool is being used;
• A calculation of the personal daily exposure in A(8) can be made using the HSE calculator or
ready reckoner;
• You will need to know the duration of exposure to do the calculation;
• You need to know the ‘trigger time’ not the full time of exposure;
Jul 14 Jul 12 Jul 09
(a) With reference to the Control of Vibration at Work Regulations 2005 explain the meaning of:
(i) Exposure Limit Value (2)
(ii) Exposure Action Value (2)
(b) A building contractor has been asked to remove a large area of concrete paving using a hand held concrete breaker. The concrete breaker has a vibration magnitude of 10m/s2.
The site manager estimates that it will take approximately 4 hours for one operative to complete this task.
Using this information AND the HSE vibration calculator below outline the practical steps the site manager should consider when determining how to complete this task with the existing equipment to comply with The Control of Vibration at Work Regulations 2005. (10)
(c) Outline other control measures that the site manager could put in place for similar work in the future. (6)
(a)
(i) For HAV the Exposure Limit Value = 5 m/s2 A(8) This is the level of vibration - averaged over an 8 hour period - which should not be exceeded. Reg 6 requires the employer to:
• ensure that his employees are not exposed to vibration above an exposure limit value; or
• if an exposure limit value is exceeded
- reduce exposure to vibration to below the limit value
- identify the reason for that limit being exceeded; and
- modify the control measures taken to prevent it being exceeded again
(ii) For HAV the Exposure Action Value = 2.5m/s2 A(8). This is the level of vibration - averaged over an 8 hour period - at which an employer is required to initiate technical and organisational control measures to reduce exposure - see CoVaW regs (Reg 4)
For WBV the Exposure Limit Value = 1.15 m/s2 A(8) For WBV the Exposure Limit Value = 0.5 m/s2 A(8)
(b) From the HSE graph it can be seen that using equipment with a vibration magnitude of 10 m/s2 for 4 hours in a day has an exposure level allocated 800 points in the HSE vibration calculator and is in the red zone ie exposure of a single operative averaged over 8 hours is above the daily ELV of 5 m/s2 A(8). In fact for a vibration magnitude of 10 m/s2 the ELV is exceeded after 2 hours work (400 points in red). Consequently, if the existing equipment is to be used the working time for a single operative would have to be reduced to 1 hour if the ELV is not to be exceeded. But even at this duration the EAV is still being exceeded and the working time would need to be a maximum of 30 minutes per day (and preferably lower ALARP) - to reduce exposure to a level at which the regs no longer applied.
In these circumstances the employer / site manager should take steps to limit the duration and magnitude ofexposure to vibration. This could be achieved by:
Reducing the amount of time the person does the job to 1 hour max per day. Alternatively job rotation - using 4 workers for 1 hour each day (with no additional vibration exposure during their 8 hour shift); even then the EAV is still exceeded; to keep below the EAV individual exposure times would need to be approx 0.5 hours per day requiring 8 different operatives if the work is to be completed in 1 day. Another option is for the work to be spread out over several days depending on numbers of operatives available (and taking account of weekly averaging).
(c) Other control measures include using an alternative method of breaking concrete (JCB?); purchase / hire lower vibration tools (to meet the ELV requirement new equipment would need to have a vibration magnitude of approx 7m/s2 if being use by a single operative for 4 hours; to stay within the EAV requires a vibration magnitude of approx 3.5m/s2); maintaining tools to reduce vibration levels; use tools with anti-vibration mounts / handles / good ergonomic design – adjustability etc to reduce grip / force required / reduce vibration transmission to hands etc; job rotation; rests / breaks; providing rest periods; finger exercises; opportunity to warm hands / fingers; provide warm clothing / gloves; provide training, information on HAVS - raise awareness of hazards and control measures, causes, symptoms, health effects, control measures etc; thermal handles / gloves; introduce a health surveillance programme (+ brief details).
Jan 14 Jul 10
A machine operator is required to work at a number of different machines during a normal 8-hour working day.
(a) Explain how a series of static measurements can be taken in the workplace and then used to estimate the operator’s daily personal noise exposure (Lep,d). (5)
(b) The result of personal dosimetry on a similar day provides an Lep,d that is 4dB(A) greater than the estimate made in (a). Outline factors that may account for the difference. (5)
(a) To obtain the operator’s Lep,d (daily personal noise dose / 8 hour time-weighted average noise exposure) Take static measurements at the operating position for each machine during normal operation using an integrating sound level meter;
This will provide the individual LAeq,t, for each machine (L1, L2, L3 etc). The LEP,d value can then be obtained using a mathematical formula: LEP,d = 10 Log [(L1/10) + (L2/10) + (L3/10)…(Ln/10)].
Alternatively if the noise levels for the individual machines are measured, together with the duration of exposure at each machine HSE’s “nomogram” can be used to give a “fractional exposure” (f) value for each machine / duration; the individual “f values” can then be added and converted into a daily personal noise dose Lepd in dB(A). The easiest way is to use the HSE noise calculator (on the HSE website) - simply input the individual static measurements and durations of exposure and the LEP,d is calculated automatically.
(b) Differences may be due to:
• personal dosimetry is more accurate - gives a better estimation of actual exposure than static measurements; static measurements taken over too short a time / not representative
• change in work routine - spends longer at certain noisier machines
• operator in a different position in relation to machines
• reflected sound from body
• operating machinery at different speeds
• uses different (noisier) work processes - different way of working / different materials / speeds
• change of circumstances - other contributory background noises present / greater levels of
reverberation / using more sensitive equipment
• errors in calibration of devices
Jul 13 Jul 11 Jan 11 Jan 09
A small printing organisation operates a number of printing machines that are located in an open plan workshop. Following a noise survey the organisation discovers that its employees are being exposed to noise levels of 86 dB(A) LEP,d.
(a) Outline the significance of this noise level to an employer. (5)
(b) Describe the range of technical AND organisational control measures that could be introduced. (15)
(a) Noise level in workshop = 86dB(A) Lepd is above the CoNaWR EAV of 85 dB(A) Lepd but below the ELV of 87 dB(A) Lepd; at 86dB(A) there is a risk of NIHL and consequent hearing damage; this could affect insurance cover / liability and also result in enforcement action & civil claims; so the employer must take steps to reduce noise level below 85dB(A) and ALARP.
(b)Technical – Source, Transmission, Receiver
• replacing older/noisier equipment with machines that emitted lower levels of noise;
• isolating the noisier machines in a separate area of the workshop;
• building a noise enclosure of suitable noise attenuating material around them;
• mounting the noisy equipment on rubber strips or dampers;
• lining the walls and floor of the workshop with acoustically absorbing material;
• applying damping to metal panels on machines;
• creating a noise haven for the employees;
• Failing the above, the provision of hearing protection, it should be chosen based on an octave
band analysis measurement of the noise emitted in order to provide the best overall reduction in exposure.
Organisational controls
• reducing exposure times by job rotation;
• designating hearing protection zones;
• providing training to employees on the risks associated with exposure to noise;
• Provide training on the fitting and maintenance of hearing protection;
• Supervise use of protection;
• introducing disciplinary procedures to deal with those employees who did not wear them;
• Health surveillance.
Jul 13
The use of hand-held vibrating tools can cause hand-arm vibration syndrome (HAVS).
(a) Describe the health effects of HAVS. (3)
(b) Outline the factors to consider when carrying out a risk assessment of employees who make extensive use of hand-held vibrating tools in their work. (7)
(a)
• MANC
• Muscular - loss of dexterity and grip; • Articular – bone and joint problems; • Neurological – numbness and tingling; • Circulatory – blanching (vibration white finger); • Carpel tunnel syndrome; • Gangrene in severe cases; • The extent of severity can be indicated by the degree of blanching and the use of grading tools such as the Stockholm scale.
(b)
Factors to consider in risk assessment
• Who may be affected (anyone at high risk)
• Existing controls in use (physical and procedural)
• The magnitude of the vibration (measured or from manufacturers’ information.comparison with the exposure action and limit values contained in the Control of Vibration at Work Regulations 2005;
• Duration and frequency of exposure to vibrating power tools
• Calculation of the dose employees are likely to be exposed to.
• Comparison to exposure limit values and action values.
• Temperature of the working environment
• Age and condition of equipment (maintenance regime)
• Health surveillance
• Any further measures necessary
• Review date for risk assessment
Jan 12 Jul 09 Jan 06 Jul 05
The figure below shows an audiogram for an adult employee.
(a) Explain what is meant by “threshold shift”. (2)
(b) Outline the significance of the shape of the audiogram. (2)
(c) Outline the benefits and limitations of audiometry as part of a hearing conservation programme. (6)
(a) Threshold shift = reduction in a person’s sensitivity to sound often caused by high noise exposures.
Can be temporary (TTS) or permanent (PTS = NIHL);
TS is measured as the difference between the hearing threshold of a subject under test and that of a healthy young adult with no hearing impairment. TS is measured as “hearing loss” in dB(A).
(b) Audiogram shows a “notch” centred around the 4kHz frequency indicating a significant hearing loss between 1 - 8kHz.
This is characteristic of NIHL - other hearing defects show a different trace on the audiogram.
(c) The benefits of audiometry include:
Provides evidence of effectiveness of hearing conservation programme;
• pre-employment screening identifies those with existing problem;
• enables identification of susceptible individuals and/or early signs of hearing loss;
• may lead to reduced insurance premiums and provides information that may be used to
defend civil claims;
• Compliance with legal requirements.
The limitations of audiometry are:
(i) it is reactive nature only identifies hearing damage after the event
(ii) resource implications - cost, time, inconvenience
(iii) it is dependent on reliable subject response, operator competence and avoidance of confounding
factors (such as temporary threshold shift, tinnitus etc)
(iv) the possibility of promoting claims by employees
(v) it cannot differentiate between NIHL caused by occupational and non-occupational exposures
Jul 10 Jan 08 Jan 07 Jan 06
The use of hand-held vibrating tools can cause hand-arm vibration syndrome (HAVS).
(a) Describe the health effects of HAVS. (4)
(b) Outline the factors to consider when carrying out a risk assessment of employees who make extensive use of hand-held vibrating tools in their work. (6)
(c) Outline a hierarchy of control measures that could be used to minimise the risks to employees of developing HAVS when using such power tools. (8)
(a) MANC • Muscular - loss of dexterity and grip; • Articular – bone and joint problems; • Neurological – numbness and tingling; • Circulatory – blanching (vibration white finger); • Carpel tunnel syndrome; • Gangrene in severe cases; • The extent of severity can be indicated by the degree of blanching and the use of grading tools such as the Stockholm scale.
(b)
identifying tools used, tasks carried out and duration of the exposure;
• the number of people involved;
• Individual susceptibility – Raynauds, smoker or an existing HAVS;
• Dose - the magnitude and frequency;
• the measurements of the vibration magnitude with the aid of an accelerometer and their comparison with the exposure action and limit values contained in the Control of Vibration at Work Regulations 2005;
• the temperature of the working environment;
• the extent of use of existing control measu
(c)
changing the process;
• using automation to avoid the use of handheld tools;
• replacing the equipment with a lower vibration model;
• the introduction of job rotation with frequent breaks from using the handheld tools;
• introducing a system of regular maintenance and lubrication to ensure vibration was kept to
its designed level;
• Instruction and training;
• providing warm clothing and a warm environment to encourage good blood circulation;
• Introduction of pre-employment health screening to identify any predisposition to vibration
related disorders.
Jul 10
A machine operator is required to work at a number of different machines during a normal 8-hour working day.
(a) Explain how a series of static measurements can be taken in the workplace and then used to estimate the operator’s daily personal noise exposure (Lep,d). (5)
(b) The result of personal dosimetry on a similar day provides an Lep,d that is 4dB(A) higher than the estimate made in (a).
Identify the factors that may account for the difference. (5)
(a) static measurements would have to be taken at the operating positions of each machine during normal operation of the machines;
• This would involve measuring the equivalent continuous A-weighted sound pressure LAeq at each machine using an integrated sound level meter;
• A note would need to be taken of the time the operator spends at each machine;
• The operator’s daily personal exposure can then be calculated using the electronic spread
sheets on the HSE web site.
(b) Differences may be due to:
• personal dosimetry is more accurate - gives a better estimation of actual exposure than static measurements; static measurements taken over too short a time / not the actual operator position was not represented when the static measurement was taken;
• different machines, materials and machine speeds were used;
• there was a presence of other noise sources;
• Static measurements taken over too short a period of time – peak levels could have been
missed;
• other significant noise exposure that might occur between jobs or during breaks were not
taken into account;
• errors were made in calibration;
• errors in the use of static measurement equipment;
• reflected sound from the body might lead to an increased measurement.
Jan 08 Jul 05
A&B Printing Ltd. operates a number of printing machines producing promotional magazines for the retail trade. They recognise that exposure to noise is a problem for all operatives within the open-plan print workshop and so the company plan to undertake a noise survey.
(a) Identify the different types of equipment that could be used to measure exposure to noise, making reference to their respective features and roles in assessing noise exposure. (10)
(b) Following the noise survey the company decide to fit an acoustic enclosure to one of the large printing machines. Outline the design features of such an enclosure. (10)
(a) Various types of equipment are used in measuring noise in the workplace - for example:
• sound pressure level meters - these come in a range of specifications the accuracy being dependent on the level of sophistication; simple devices give a “real time” measurement of instantaneous sound
pressure levels in dB(A) by measuring fluctuations in air pressure and converting these to an analogue or digital readout. These are best suited to situations in which the noise levels are reasonably constant
- integrating meters have the added feature that they can integrate the sound pressure levels of a period of time to give a time weighted average reading in dB(A) (Leq or Lepd). These are better suited to situations where there is significant fluctuation in noise levels. Some meters are also capable of measuring peak noise values an applying other weighting factors eg dB(C). More sophisticated devices can apply filters to obtain octave band analysis of the noise; this enables measurement of the sound levels in particular frequency ranges. These devices are generally used to take static or area measurements of noise in particular locations or around particular machines.
- personal noise dosimeters (dosimeters) are devices which are carried around by the worker with the microphone attached to the lapel as a means of measuring personal noise dose over a specific period. Personal noise meters give a more reliable and accurate measurement of a person’s noise dose than can be achieved via static measurements, particularly where the worker is peripatetic and subject to variable noise levels throughout the working day.
(b)
double skin construction with the walls and top being made of sound insulating material;
• robust enough to withstand the working environment;
• double glazing to be fitted where windows were considered to be essential;
• the use of flexible connectors in pipes and ducts leading into and out of the enclosure to form
vibration breaks;
• the enclosure should be effectively sealed at floor level;
• the internal surfaces should be lined to prevent reverberant build up;
• any ducts into the enclosure should be lined with absorptive material;
• ventilation of the enclosure was required, it might be provided by means of acoustic louvers;
• The printing machinery would need to be mounted on dampers;
• operating controls situated on the outside of the enclosure;
• the material entry and exit points soundproofed;
• Removable panels would need to be fitted to the enclosure to provide access for
maintenance.
