Exam January 2009 Unit IB

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January 2009

Examiners’ Report NEBOSH International Diploma in Occupational Health and Safety (Unit IB)

Examiners’ Report NEBOSH INTERNATIONAL DIPLOMA IN OCCUPATIONAL HEALTH AND SAFETY Unit IB – International control of hazardous agents in the workplace JANUARY 2009




General comments


Comments on individual questions


© 2009 NEBOSH, Dominus Way, Meridian Business Park, Leicester LE19 1QW tel: 0116 263 4700

fax: 0116 282 4000

email: [email protected]

website: www.nebosh.org.uk

The National Examination Board in Occupational Safety and Health is a registered charity, number 1010444 T(s):exrpts/J/J-B0901




NEBOSH (The National Examination Board in Occupational Safety and Health) was formed in 1979 as an independent examining board and awarding body with charitable status. We offer a comprehensive range of globally-recognised, vocationally-related qualifications designed to meet the health, safety, environmental and risk management needs of all places of work in both the private and public sectors. Courses leading to NEBOSH qualifications attract over 25,000 candidates annually and are offered by over 400 course providers in 65 countries around the world. Our qualifications are recognised by the relevant professional membership bodies including the Institution of Occupational Safety and Health (IOSH) and the International Institute of Risk and Safety Management (IIRSM). NEBOSH is an awarding body recognised and regulated by the UK regulatory authorities: • • •

The Office of the Qualifications and Examinations Regulator (Ofqual) in England The Department for Children, Education, Lifelong Learning and Skills (DCELLS) in Wales The Council for the Curriculum, Examinations and Assessment (CCEA) in Northern Ireland

NEBOSH follows the “GCSE, GCE, VCE, GNVQ and AEA Code of Practice 2007/8” published by the regulatory authorities in relation to examination setting and marking (available at the Ofqual website www.ofqual.gov.uk). While not obliged to adhere to this code, NEBOSH regards it as best practice to do so. Candidates’ scripts are marked by a team of Examiners appointed by NEBOSH on the basis of their qualifications and experience. The standard of the qualification is determined by NEBOSH, which is overseen by the NEBOSH Council comprising nominees from, amongst others, the Health and Safety Executive (HSE), the Department for Education and Skills (Df ES), the Confederation of British Industry (CBI), the Trades Union Congress (TUC) and the Institution of Occupational Safety and Health (IOSH). Representatives of course providers, from both the public and private sectors, are elected to the NEBOSH Council. This report on the Examination provides information on the performance of candidates which it is hoped will be useful to candidates and tutors in preparation for future examinations. It is intended to be constructive and informative and to promote better understanding of the syllabus content and the application of assessment criteria. © NEBOSH 2009

Any enquiries about this report publication should be addressed to: NEBOSH Dominus Way Meridian Business Park Leicester LE10 1QW Tel: 0116 263 4700 Fax: 0116 282 4000 Email: [email protected]



General comments

Many candidates are well prepared for this unit assessment and provide comprehensive and relevant answers in response to the demands of the question paper. This includes the ability to demonstrate understanding of knowledge by applying it to workplace situations. There are always some candidates, however, who appear to be unprepared for the unit assessment and who show both a lack of knowledge of the syllabus content and a lack of understanding of how key concepts should be applied to workplace situations. In order to meet the pass standard for this assessment, acquisition of knowledge and understanding across the syllabus are prerequisites. However, candidates need to demonstrate their knowledge and understanding in answering the questions set. Referral of candidates in this unit is invariably because they are unable to write a full, well-informed answer to one or more of the questions asked. Some candidates find it difficult to relate their learning to the questions and as a result offer responses reliant on recalled knowledge and conjecture and fail to demonstrate a sufficient degree of understanding. Candidates should prepare themselves for this vocational examination by ensuring their understanding, not rote-learning pre-prepared answers. Recurrent Problems It is recognised that many candidates are well prepared for their assessments. However, recurrent issues, as outlined below, continue to prevent some candidates reaching their full potential in the assessment. −

Many candidates fail to apply the basic principles of examination technique and for some candidates this means the difference between a pass and a referral.

In some instances, candidates are failing because they do not attempt all the required questions or are failing to provide complete answers. Candidates are advised to always attempt an answer to a compulsory question, even when the mind goes blank. Applying basic health and safety management principles can generate credit-worthy points.

Some candidates fail to answer the question set and instead provide information that may be relevant to the topic but is irrelevant to the question and cannot therefore be awarded marks.

Many candidates fail to apply the command words (also known as action verbs, eg describe, outline, etc). Command words are the instructions that guide the candidate on the depth of answer required. If, for instance, a question asks the candidate to ‘describe’ something, then few marks will be awarded to an answer that is an outline.

Some candidates fail to separate their answers into the different sub-sections of the questions. These candidates could gain marks for the different sections if they clearly indicated which part of the question they were answering (by using the numbering from the question in their answer, for example). Structuring their answers to address the different parts of the question can also help in logically drawing out the points to be made in response.

Candidates need to plan their time effectively. Some candidates fail to make good use of their time and give excessive detail in some answers leaving insufficient time to address all of the questions.

Candidates should also be aware that Examiners cannot award marks if handwriting is illegible.



UNIT IB – International control of hazardous agents in the workplace

Section A – all questions compulsory

Question 1

Outline the possible functions of an occupational health service within a large manufacturing company.


The possible functions of an occupational health service that could have been outlined include pre-employment health screening or other medical examinations (for example, of employees returning to work following accidents or of those such as transport drivers whose work demands particular physical competencies), biological monitoring and health surveillance. The service would also very likely have a role in contributing to health and safety policies, providing specialist input to risk assessments and health education and training programmes, carrying out sickness and absence monitoring and keeping health records, managing first-aid provision, implementing rehabilitation programmes and liaising with other professionals such as local general medical practitioners and enforcement officers. Other possible functions, depending on the organisation and its activities, might include immunisation, drug and alcohol screening and involvement with environmental monitoring programmes. A few candidates were able to identify the role of occupational health staff in conducting medical examinations and health surveillance but were then not able to go much further and outline other likely functions, in particular how occupational health expertise could be used in promoting and managing health at work. In general, however, the question was reasonably well answered and most candidates were able to provide a good range of possible functions of an occupational health service. It was not necessary to outline the roles of different personnel within an occupational health department as this is outside the scope of the question.

Question 2


(b) (c)

Outline why transport (duct) velocity is an important parameter to measure when assessing the efficiency of a local exhaust ventilation (LEV) system.


Outline the methods that can be used to measure transport velocity in an LEV system.


Identify other parameters that may be measured to determine if the LEV system is working as designed.


Part (a) of the question was concerned only with the parameter of duct velocity. Marks were available for identifying that duct velocity must be sufficient to keep the particles airborne and, if this is not the case, then particles may settle out in the ductwork and affect the overall efficiency of the system.



Part (b) required an outline of the methods that may be used to measure duct velocity in an LEV system and it was expected that candidates would outline the principles and use of both a thermal anemometer and a pitot-static tube. The choice of instrumentation is governed by the air velocity in the duct with a thermal anemometer being more suitable if this is less than 3ms-¹ (though knowledge of the actual figure was not a key requirement). The operating principles of each instrument were required – in terms of the anemometer responding to the cooling effect of airflow and the pitot-static tube measuring, via a pressure gauge, velocity pressure which can then be converted to velocity. Regarding the actual use, the importance of finding a suitable sampling point should have been mentioned. Any such sampling point should be in an area of ducting that is free from turbulence such as a long stretch of ducting. Reference to a swinging vane anemometer (with probe) was also appropriate. However, reference to rotating vane anemometers was inappropriate in response to this part of the question. Part (c) gave scope for candidates to recall knowledge of other parameters relating to LEV systems such as capture velocity, pressure differential across the filter and fan speed. Measurement of the level of contaminants in the workplace air, power consumption and emission levels from the exhaust may also give an indication of the efficiency of an LEV system, all other things being equal. There were only a few candidates who displayed the required level of knowledge in answering this question. The remainder did not appear to be familiar with either the principles of local exhaust ventilation or the methods for measurement.

Question 3

A research laboratory undertakes intentional work with biological agents such as Ebola and Lassa viruses. These biological agents are categorised as extremely hazardous, being placed in the highest hazard group. Outline a range of technical controls that should be used to minimise the risks to those working in the laboratory, where elimination or substitution of the hazard is not possible.


In answering this question, candidates were expected to outline technical control measures such as: the separation of the laboratory from other activities in the same building; input and extracted air to be passed through a HEPA (high efficiency particulate air) filter; access to be restricted to authorised persons by means of a security pass or swipe card system; the work area to be sealable to permit disinfection and to be maintained at an air pressure negative to atmosphere; all surfaces to be impervious to water, easy to clean and resistant to acids, alkalis, solvents and disinfectants; secure storage to be provided for the biological agents; an observation window (or equivalent) to be fitted so that the occupants can be seen at all times; a microbiological safety cabinet with sealed front and glove port access to be used to carry out the work; a facility such as an autoclave to be provided for rendering waste safe; provision of an incinerator for disposal of animal carcases on site (if applicable); the laboratory should be provided with its own equipment and finally the provision of appropriate and adequate hand washing facilities. There were not many good answers provided for this question with few candidates appreciating either the hazards involved or the precautions that should be taken.



Question 4


Use the data below to calculate the 8 hour Time-Weighted Average (TWA) exposure to flour dust for a bakery operative. Your answer should include detailed working to show your understanding of how the exposure is determined.

Working Period (Total shift time = 8 hours) 08.00 – 10.30 10.30 – 10.45 10.45 – 12.45 12.45 – 13.45 13.45 – 15.45 15.45 – 16.00

Tasks undertaken by bakery operative Weighing ingredients Break Charging the mixers Lunch Cleaning equipment Assisting maintenance staff


Exposure to Flour dust (mg/m3) 14 10 2.5 0 (assumed)

Assuming that exposure is zero during break times and lunch time Also assume that a legally enforceable Exposure Limit (8 hours TWA) of 10 mg/m3 is applicable to flour dust


The bakery changes the working patterns to the extent that the operative now only charges the mixer. In addition, shift times have been altered to a 10 hour shift, which includes a 1 hour lunch break where the exposure is assumed to be zero. Using the relevant data above, recalculate the equivalent 8 hour TWA exposure in their new role AND comment on the legal implications of this change.


Answers to the first part of the question should have shown how the 8 hour TWA exposure to flour dust for a bakery operative could be calculated firstly by multiplying together each time period and exposure including the periods of zero exposure, then adding the results of the calculations together and finally dividing by eight. This would give an answer of 7.5 mg/m³. Numerically, this could be expressed as: ((14 x 2.5) + (0 x 0.25) + (10 X 2) + (0 X 1) + (2.5 X 2) + (0 X 0.25))/8 = (35 + 0 + 20 + 0 + 5 + 0)/8 = 60/8 60/8 = 7.5 mg/m³. For part (b), a similar calculation would have shown an exposure of 11.25 mg/m³ viz: ((10 x 9) + (0 x 1)) = 90/8 = 11.25 mg/m³. The change in the mode of working has increased the individual’s exposure so it is now more than the legal exposure limit. The employer is no longer adequately controlling exposure and must introduce additional controls. While the first part of the question was well answered, many candidates became confused with the calculations required for the second part and arrived at a wrong result. They were then not in a position to comment on the legal implications of the change in the working pattern.



Question 5



Identify the way in which lasers are classified according to their hazard.


Low power lasers are widely used to read bar-code labelled products at checkouts in retail premises. Outline the design features that should be incorporated into these laser products to ensure their safe operation and maintenance.


In answer to part (a) of the question, candidates were expected to identify that the classification of lasers is defined in an IEC standard – IEC 60825 (also EN 60825). The classifications are based on accessible emission levels with the power of the lasers measured in milliwatts (mW). There are seven different classifications – 1, 1M, 2, 2M, 3B, 3R, and 4 and marks were awarded to those who additionally identified the graduation in the level of hazard associated with each class from Class 1 – the lowest level to Class 4 lasers which pose the greatest hazard. For part (b), design features that should be incorporated into the laser products to ensure their safe operation and maintenance include the laser having no greater power than Class 1; the use of embedded systems; the fitting of a protective housing with trigger operation on the hand held version; incorporating a key control with interlock to the power source; the provision of signage and the appropriate positioning of the laser, including hand-held equipment, to avoid eye-level exposure. This question was not well answered with many candidates lacking any knowledge of laser classification or being able to visualise the practical scenario involving bar code readers.

Question 6

A company has decided to close its offices and allow the 30 workers to work from home. The company will provide each worker with their own portable (laptop) computer for use at home and on their daily visits to customers. Outline the factors which should be considered to minimise ergonomic risks to their workers when purchasing these laptops AND bringing them into use.


This question focussed on the ergonomic considerations involved in the use of portable computers and the factors which should be considered to minimise risks to users. The initial selection and purchase of the equipment is of prime importance if the computer is to be used on the move where consideration would need to be given to the provision of as large a screen as possible; to the weight of the equipment; to the provision of light weight carrying cases or trolleys and to the provision of friction pads to stop the computer slipping during use. During home use consideration would have to be given to the provision of a separate mouse and keyboard and a separate screen or docking station as well as the provision of other workstation equipment such as a chair and desk.



Other factors which would have to be considered would be the involvement of the users in the selection of the equipment; revising the display screen equipment and manual handling risk assessments to reflect the new mode of working and providing training on the use of the portable machines with reference to carrying out risk assessments on workstations created at home or on the move; on minimising the ergonomic risks associated with correct set-up and use, for example on the importance of taking regular breaks and on minimising the manual handling risks associated with carrying the laptop. Answers to this question were to an acceptable standard though some candidates did not focus wholly on the given scenario and wrote at length about software and ergonomic issues associated with a workstation rather than concentrating on the issues associated with the use of a laptop.

Section B – three from five questions to be attempted

Question 7

A small printing company operates a number of printing machines which are located in an open plan workshop. Following a noise survey the company discovers that their workers are being exposed to high average daily noise levels. The noise levels exceed regulatory exposure limits. (a)


Describe the acute and chronic physiological effects of exposure to high noise levels on the individual. Explain what steps the company should take to protect workers. In your answer clearly describe the range of technical and organisational control measures that could be introduced.

(4) (16)

In answering part (a) of the question, candidates were expected to outline effects such as tinnitus, a ringing in the ears that may be chronic or acute; threshold shift which can again be temporary or permanent; and noise induced hearing loss where those affected suffer a loss of sensitivity to sounds in the speech range. For part (b), candidates should have referred to the need to reduce exposure by means other than the provision of hearing protection and could have described technical controls such as: replacing older/noisier equipment with machines that emitted lower levels of noise; isolating the noisier machines in a separate area of the workshop and 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 and applying damping to metal panels on machines; and creating a noise haven for the employees. If, even after taking the above measures, the provision of hearing protection was found to be necessary, 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 include reducing exposure times by job rotation; designating hearing protection zones; providing training to employees on the risks associated with exposure to noise and on the fitting and maintenance of hearing protection; ensuring hearing protectors, once issued, were used and introducing disciplinary procedures to deal with those employees who did not wear them. Answers were generally to a reasonable standard with most candidates able to use a generic noise control approach to the specific example in the question.



Question 8



Describe the ways the body may defend itself against inhaled dusts.


A company uses a range of coloured powders in the manufacture of paints. These powders are added directly to a mixing vessel from sacks. The company is concerned about the level of exposure to its workers from the powders during this part of the process. Outline the practical control measures that could be used to minimise exposure to these powders during the addition.


The body’s first line of defence against inhaled dusts is the nasal hairs which trap and filter out dust particles greater than ten microns in size. Mucus in the nose and mouth also traps these particles which are subsequently ejected by sneezing, blowing the nose and spitting. Dust particles between five and ten microns tend to settle in the mucus covering the bronchi and broncioles and are wafted upwards by tiny hairs – the ciliary escalator – towards the throat. They are then coughed and spat out. Particles smaller than five microns are more likely to reach deep into the lungs, as far as the alveoli. These particles are ingested by macrophages – a type of white blood cell – in a process known as phagocytosis and transported back to the ciliary escalator or to the lymphatic system. They may also be transported across the alveolar membrane into the blood stream. In answering part (b), candidates should have recognised that elimination of the coloured powder was not an option since the colour range was required. Consequently they were expected to outline practical control measures such as introducing the colouring agent in a pellet or dye solution form. If this was not possible, then the powder could be fed into the mixing vessel by means of an automated feed system (such as a screw conveyor). Local exhaust ventilation is also an option. A vacuum system would need to be introduced to clear up spillages and employees should be provided with personal protective equipment such as overalls, gloves and goggles. Some form of respiratory protection would also have to be provided. If the dust was thought to be nuisance only, then a particle filtering face piece – a disposable face mask – changed on a regular basis could suffice. However, a mask and filter respirator would have to be worn if the powder were found to be harmful. Adequate supervision to enforce use is important. Use of appropriate handling techniques to minimise dust creation when emptying sacks was also relevant. The first part of the question, based on a theoretical concept, was well answered. However, the practical aspect of the scenario in the second part caused problems.



Question 9

It is often necessary to monitor a worker’s personal exposure to hazardous substances using a variety of methods including: gravimetric analysis; microscopy; chemical analysis. For EACH of these three measurement principles: (a)


identify a type of hazardous substance, AND suggest a typical workplace situation, where such a measurement may be necessary;


outline the type of equipment and the methodology used to determine the worker’s personal exposure to the hazardous substance.


For part (a) of the question, candidates should have identified that the gravimetric method for measuring personal exposure to hazardous substances may be used for measuring total inhalable or respirable dusts for instance in a woodworking workshop or in the manufacture of chemicals. Microscopy would be used for the measurement of fibres such as following the accidental disturbance or planned removal of asbestos. Chemical analysis is used in the measurement of gases, vapours, fumes and some dusts in workplaces such as laboratories or those involved in the manufacture of chemicals. Part (b) asked candidates to outline the equipment and methodology used in each of the three monitoring methods. With gravimetric, a filter on a sampling head attached to a pump is used. There are various types of sample head depending on the type of dust being determined (eg 7 hole, , IOM and the cyclone). The filter is weighed before and after sampling and the concentration, expressed in mg/m³, is determined from the weight gain and the volume of air drawn through the pump during the sampling period. With microscopy, a membrane filter fitted on an appropriate sampling head (eg cowled) is attached to a pump. After sampling is completed, a phase contrast microscope is used to count the fibres. The number of fibres in a known proportion of the sample is calculated and extrapolated to the whole sample with the result being expressed as fibres per millilitre of air (f/ml). As far as chemical analysis is concerned, there are numerous active and passive collection devices. For example, a tube or sampling head with a filter impregnated with an adsorbing material such as charcoal, tenax or silica attached to a pump. After sampling it is desorbed and analysed in a laboratory. Analysis techniques include mass spectrometry, IR spectrometry and gas chromatography. Concentrations are expressed in parts per million or milligrams/m³. General points associated with each monitoring method include the necessity: to calibrate the pumps used; to draw a known volume of air through the filter or tube; to take a number of samples to minimise errors in measurement; and to ensure the sampling head was placed in the breathing zone. This was not a popular question. Answers generally demonstrated a lack of technical knowledge of the measuring equipment involved.



Question 10

A slightly corrosive solution is used as a treatment in part of a manufacturing process. The solution is applied by hand brushing. For this process, other methods of application are not practicable. (a)



Outline the factors that should be considered in the selection of personal protective equipment to adequately protect the skin and the eyes of those involved in the process.


Outline the content of a training programme that will assist workers to use the personal protective equipment correctly.


Identify a range of practical measures (other than training) that can be taken to encourage the use of the personal protective equipment and maintain its effectiveness.


In answering part (a) of the question, a logical approach would have been to outline the factors to be considered in the selection of personal protective equipment firstly for the hands, then for the face and eyes and finally for the rest of the body. However, firstly, applicable to all forms of protection are factors such as: consultation and user trials; comfort/fit; conformity to appropriate performance standards and appropriate chemical resistance. For the selection of protective gloves, additional relevant factors were the chemical breakthrough time; the level of dexterity required for the task; the length of the glove to afford adequate protection; the durability of the gloves; the need to ensure that a suitable range of sizes is available for the various users; and any employee allergies to the glove material or any other skin problems. In the selection of eye protection, relevant factors were the risk of splashing the face as well as eyes; the need to use goggles or a face shield (glasses inadequate); and their compatibility with other protective equipment if this was required. In the selection of body protection, candidates should have referred to aprons and/or overalls and appropriate footwear. Good answers to the second part of the question would have identified that employees should receive training in topics such as: the health risks of the chemical in use; the type of personal protection to be used and the reason for its use; the methods to be used for putting on and taking off the equipment without causing contamination including decontaminating or discarding gloves after use; the methods of examining the equipment for damage or degradation, particularly gloves, and for reporting defects and obtaining replacements; how to store the equipment correctly and finally how to carry out self examination of the skin and the action to be taken if problems were to occur. For part (c), candidates were expected to identify practical measures such as: management leading by example; employees being involved in the selection of the equipment; ensuring the availability of a range of sizes in gloves and fully adjustable face shields; ensuring employees were required to sign for their equipment and maintaining records of issue; issuing the equipment on a personal basis and providing adequate storage facilities; using propaganda, signs and posters and incentive schemes; monitoring compliance in the use of the equipment with a recognised code of discipline for non-use; and finally monitoring the effectiveness of the equipment issued and replacing it with an alternative type if problems were encountered. While this was a popular question and generally well answered, those who were not so successful were those who found it difficult to adapt their standard generic personal protective equipment answer to the actual scenario in the question.



Question 11

You are a health and safety advisor to a railway train operating company. You have been asked to prepare a company policy on drug misuse. Outline the key points that such a policy should include.


In the preparation of a policy on drug misuse for a railway train operating company, candidates should have outlined key points such as: a general statement of aims, for instance the employer expects all employees to ensure that drug misuse does not have a detrimental effect on their work; responsibilities for carrying out the policy (managers, employees, occupational health counsellors etc) and who is covered by the policy (employees, contractors, visitors); a definition of drug misuse that includes misuse of prescription drugs as well as prohibited drugs; the requirement for notification to management by those employees taking prescription drugs; a reporting procedure for employees if they suspect colleagues are taking or are under the influence of drugs; circumstances in which drug testing will be carried out such as preemployment, randomly as a precautionary measure for all drivers and track side workers and following any track side or train accident or incident; the practical arrangements for carrying out testing including those for peripatetic workers; the arrangements for handling samples taken for drug testing; the procedures to be followed after a positive test or a refusal to take a test with a clear statement on the sanctions to be taken in such circumstances; details of an appeals procedure; an indication of the support and help available to employees who have a drug problem together with the recognition that treatment may result in absence which will be treated as normal sick leave; details of arrangements for re-instatement and return to work following treatment and a statement assuring employees of confidentiality. This was a popular but not well answered question with many candidates unable to suggest an acceptable range of key points to be included in the policy.



The National Examination Board in Occupational Safety and Health Dominus Way Meridian Business Park Leicester LE19 1QW telephone +44 (0)116 2634700 fax +44 (0)116 2824000 email [email protected] www.nebosh.org.uk

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