B3 Flashcards
Jan 20 Jan 08
Outline reasons why respiratory protective equipment (RPE) may not provide the level of protection that is stated by the manufacturer when it is being used. (10)
RPE may not provide stated level of protection because:
• incorrect type for hazard - dust masks used for vapours,
• wrong cartridge etc; not used correctly –
• poor fit / inadequate seal – due to facial hair, jewellery etc;
• damaged / inefficient;
• contaminated – due to inadequate care / storage / maintenance;
• cartridge saturated;
• incompatible with or effectiveness reduced by other PPE;
• low air flow in powered equipment - battery low etc;
• effectiveness compromised by mixed exposures;
• manufacturer figures are obtained in “ideal conditions”
Jul 19 Jan 17
Dilution ventilation can be used to control certain types of hazardous substances generated in a workplace.
(a) Outline circumstances when dilution ventilation may be appropriate as a control measure to reduce exposure to a hazardous substance. (3)
(b) Describe the design features of the air input for a dilution ventilation system. (3)
For a dilution ventilation system to be effective the number of air changes achieved must be sufficient.
(c) Calculate the number of air changes per hour for a dilution ventilation system with the following specification:
Workplace dimensions 10mx 10m x 3 m
Volume of Air throughout each hour 3000m3
Required number of air changes per hour 10-15
Comment on the effectiveness of the specified dilution ventilation system in controlling exposure to a hazardous substance. (2)
(a) Dilution ventilation is generally suitable with:
• low toxicity substances,
• low density such as fumes, vapour or gas,
• small quantities and uniform concentration (steady rate)
(b) Air input is usually provided by means of windows, doors or vents. There should be sufficient inputs
spread around the work area such that there are no dead spots where air is not diluted.
(c,i) Volume = 300m3
3000m3/hr therefore represent 10 air changes per hour (3000/300)
c,iiThe effectiveness of the dilution ventilation system is within the specified number of air changes of 10 to 15. However, it is right at the lower end of that and some areas may in fact be lower than the 10 measured. Therefore changes should be made to ensure an increase the air throughput to ensure safe conditions
Jul 18 Jul 13 Jan 11 Jan 07
(a) Explain the circumstances when it may be necessary to use RPE as a control measure to reduce exposure to a hazardous substance. (6)
Employees carrying out a short duration task involving a corrosive vapour of ammonia have been provided with RPE.
The employer used the following information when selecting the RPE:
Concentration of ammonia in the workplace 290ppm
WEL for Ammonia. 35ppm (min (STEL)
Assigned protection factor (APF) for RPE 20
(b) Explain how the employer can use this information to determine if the choice of RPE is appropriate. (4)
(c) Outline other factors that the employer should consider when selecting RPE for use during this task. (10)
(a) RPE should only be used:
• Where an inhalation exposure risk remains after you have put in place other reasonable controls
(residual risk);
• While you are putting in place other control measures (interim measures);
• For emergency work or temporary failure of controls where other means of control are not reasonably
practicable;
• For short-term or infrequent exposure, such as during maintenance work, where you decide that other
controls at the source of the exposure are not reasonably practicable.
(b) If Concentration is 280ppm and assigned APF is 20 then exposure is 280/20 or 14ppm. This shows that the exposure will be well below the WEL of 35 and therefore provides a good safety factor.
(c) Other factors to consider are:
• The nature of contaminant; is it a dust, vapour, etc., is there an occupational exposure limit, is the
contaminant a carcinogen, mutagen or asthmagen and is it toxic on inhalation?
• What is the expected duration of use of the RPE? Short duration use might allow the selection of a
lower quality item whereas long–term or continual use will require a much higher specification item to be
used.
• What is the type and nature of the work being carried out when wearing the RPE? Is it heavy or light
work, what degree of movement is needed, are there space constraints that might prevent the use of
larger bulky items?
• Are there compatibility issues with other PPE needed? If so, how can these issues be overcome
without compromising the effectiveness of all PPE items?
• What about ease of maintenance? Some items of RPE require a high level of maintenance and
therefore should only be selected where this maintenance is available and adequately resourced.
• What standards exist for the RPE and does it meet those standards? i.e. certified to the relevant
international standard.
• What is the nature of the workforce? Are they capable of using the chosen items to an acceptable
standard and have they been consulted and involved in the selection (user acceptability)?
• Do members of the workforce have facial hair or markings that could prevent a good seal between the
wearer’s face and the RPE?
• Do members of the workforce have any pre-existing medical conditions?
Jul 18
Schedule 2A of the Control of Substances Hazardous to Health Regulations 2002 (COSHH) sets out eight ‘principles of good practice’ for controlling exposure to hazardous substances. One of the eight principles is: “Choose the most effective and reliable control options which minimise the escape and spread of substances hazardous to health.”
(a) Explain why the use of personal protective equipment (PPE) is often less effective as a control option than installing local exhaust ventilation (LEV). (7)
(b) Outline THREE other ‘principles of good practice’. (3)
(a) The hierarchy of Controls has Engineering controls higher than the use of PPE. The effectiveness (and reliability) is greater for control measures at the top of the hierarchy compared to those near the bottom As well as being part of COSHH, the Management of Health & Safety at Work Regs 1999 state that employers should employ the principles of prevention when selecting prevention and protection measures. One of these principles is to prioritise the use of collective measures over individual measures.
Reasons why PPE may be less effective than LEV include
• PPE only protects the individual whereas LEV protects all those in the area
• PPE may be unsuitable type or provide insufficient protection
• PPE may not face fit all people as well particularly if wearing beards, spectacles other PPE
• Some people may be awkward/disruptive and not wear PPE correctly
• LEV minimises spread of the hazardous substance and can remove it at source
(b) Any 3 from:
• Design and operate processes and activities to minimise emission, release and spread of substances hazardous to health.
• Take into account all relevant routes of exposure- inhalation, skin absorption and ingestion- when developing control measures.
• Control exposure by measures that are proportionate to the health risk
• Where adequate control of exposure cannot be achieved by other means, provide, in
combination with other control measures, suitable personal protective equipment.
• Check and review regularly all elements of control measures for their continuing effectiveness.
• Inform and train all employees on the hazards and risks from the substances with which they
work and the use of control measures developed to minimise the risks.
• Ensure that the introduction of control measures does not increase the overall risk to health
and safety.
Jul 16 Jan 11 Jan 07
An airborne contaminant has a Workplace Exposure Limit (WEL) of 10ppm, 8 hour time-weighted average (TWA). Engineering controls have been introduced but the airborne concentration of the contaminant in a workshop has been measured at 180ppm, 8 hour TWA. The occupational hygienist has selected a piece of respiratory protective equipment (RPE) with an assigned protection factor (APF) of 20, which is to be worn temporarily by all employees in the contaminated area.
(a) Using the data above outline how the hygienist could have calculated the APF and outline whether the hygienist has made an appropriate selection of RPE. (4)
(b) Outline other factors that should be taken into account when selecting appropriate RPE. (6)
(a) APF is a measure of the degree of protection provided by RPE. The hygienist needs to select RPE with an APF sufficient to reduce employee exposure to the WEL (or lower) – in other words to reduce the concentration from 180ppm to (at least) 10 ppm. This requires an 18 fold reduction in concentration (180/10 = 18) so the hygienist must select RPE with an APF of at least 18. Selecting RPE with an APF of 20 gives a 20-fold reduction in the concentration of a contaminant ie 180ppm/20=9ppm - which is below the WEL.
Concentration of contaminant in workplace air = 180ppm
APF for RPE = 20 (ie RPE reduces airborne concentration by a factor of 20) Therefore employee exposure when wearing the RPE will be 180/20 = 9ppm
So the hygienist has made an appropriate choice. (b) • Manufactured to an appropriate standard; • Allow for communication or movement; • Consultation and user trials; • Comfort; • The storage needs; • The maintenance needs; • Face fit test required; • Training;
Jul 14 Jan 12
A grounds maintenance contractor is selecting eye protection to wear during grass strimming.
(a) Describe the specific features of the eye protection required for this task. (7)
(b) Outline the arrangements the contractor should put in place when the selected eye protection is in use. (3)
(a) Task described involves probability of impact from a variety of directions - so goggles or a face shield required; need to have good mechanical and impact strength, be shatterproof with medium energy impact (B), be adjustable to allow appropriate fit and comfort and be compatible with other personal protective equipment such as hearing, head or respiratory protection. Other features to consider: the optical class of the lenses - resistance to misting and surface damage - resistance of the frames to dusts. Eye protection should be CE marked and comply with a recognised standard.
(b) arrangements should be made for the provision of training in its use and its correct fitting with other equipment; for the cleaning and storage of the equipment and for reporting defects and providing replacements when these are seen to be necessary. Additionally, measures should be taken to ensure that the protection is used at all times when grass strimming is being carried out with disciplinary action being taken for non-use.
Jan 14 **********
Local exhaust ventilation (LEV) and dilution ventilation are two control measures that may be considered when reduction of personal exposure to hazardous substances is required in a workplace.
(a) Explain how dilution ventilation can reduce personal exposure to hazardous substances. (3)
(b) Identify circumstances when the use of dilution ventilation may not be an appropriate control measure. (3)
(c) LEV may be used instead of dilution ventilation and LEV systems can contain an air cleaning device. Fabric filters and electrostatic precipitators are two types of air cleaning device that may be
found in LEV systems. For EACH type of air cleaning device:
(i) explain how they operate to remove or reduce the contaminant; (6)
(ii) identify a type of contaminant that the device is designed to remove. (2)
(d) Explain how the effectiveness of an air cleaning device can be determined. (2)
(e) Identify FOUR other components of an LEV system. (4)
(a)DV / general ventilation = “fresh air” from open windows / doors / vents / fans / general air movements; reduces exposure by dispersion / dilution / diffusion of low risk (low toxicity / small quantity) gases, vapours, odours, contaminants - results in reduced concentration in air
(b)DV not appropriate for high toxicity / large quantities / particulates or substances with chronic health effects
• Operators are in close contact with the source of contamination;
• Substances with low WELs;
• Rate of formation of a gaseous substance is low;
(c) See HSG 258: Controlling airborne contaminants at work, a guide to local exhaust ventilation, maintenance, examination and testingFabric Filters
• Uses a sock or bag to filter out the particulates (similar to a vacuum cleaner);
• Dusty air passes one way through a fabric layer that is flexible and porous.
• The fabric may be constructed and treated to carry electrostatic forces which help attract and
retain dust.
Electrostatic precipitators
(i) Fabric Filters
• Suitable for dry dusts. Electrostatic precipitators
• Suitable for fine dusts, but unsuitable for heavy contamination.
They give dust and fume particles an electrical charge and attract them onto collecting surfaces with an opposite charge;
Cleaned air flows out of the device;
(d)
• Measure a pressure drop using a manometer;
• A large pressure drop may indicate a blockage;
(e)
• Hood - Enclosed, capture or receiving - This is where the contaminant cloud enters the LEV.
• Ducting - main or branch - This conducts air and the contaminant from the hood to the
discharge point.
• Fan/motor - The ‘engine’ that powers the extraction system;
• Discharge - This releases the extracted air to a safe place
Jan 13 Jul 10 Jul 06
You have been sent a copy of a “local exhaust ventilation (LEV) examination and test report” conducted by an external organisation. The report relates to an LEV system in one part of your company’s production area. The production manager has asked you to comment on the suitability of this report before the company commissions further LEV examination work throughout the rest of the factory.
(a) Outline the measurements that you would expect to have been taken as part of the examination and test of the LEV system. (4)
(b) In addition to these measurements outline other information that should be contained in the report. (16)
(a) • Face velocity across the hood or opening; • Transport velocity in the ducting; • Static pressure in the hood or duct; • Fan/motor speed;
(b) An adequate LEV inspection report should include:
• a scale drawing / plan of the system
• details of the agents it is designed to control
• details of its general condition - visual examination - corrosion, cracks, modifications
• results of smoke tests / leak tests
• the technical specifications of hood, ducting, fans (type - axial flow or /centrifugal; power rating) & filters
• details of the equipment used to carry out the inspection + calibration procedures
• measurements of static and dynamic pressures - pitot static tube; face velocities (m/s); capture
velocities (m/s); flow volume rates (m3/s); pressure drop across the filter / system; power consumption
• reference to relevant legislative requirements - COSHH reg 9 - thorough test and examination at 14
monthly intervals
• details of the qualifications of the person(s) carrying out the inspection / compiling the report
• an indication of whether the LEV system is performing to the required standard
• details of any repairs, improvements needed
Comment: Question does not ask for detailed descriptions of how the performance of an LEV system is measured or the equipment used. [See notes - Maintenance, examination and testing of LEV: Information required of an LEV system (HSG)]
Jul 12 Jan 09 Jul 05 ******
An LEV system is used to reduce workers’ exposure to dust.
(a) Identify three visual inspection methods that provide a qualitative assessment of the
effectiveness of the LEV system (3)
Transport velocity is one quantitative measure of the effectiveness of an LEV system.
(b) Outline why transport (duct) velocity is an important parameter to measure when assessing the efficiency of a local exhaust ventilation (LEV) system. (2)
(c) Outline the methods that can be used to measure transport velocity in an LEV system. (5)
(a) Smoke bomb - smoke being drawn into system; Tyndall light beam; leak test - smoke escape; build up of dust on surfaces; signs of damage, corrosion, inspect the condition of the filter,check monitors/alarms are working
(b)
• Duct velocity must be sufficient to keep the particles airborne;
• If this is not the case, particles may settle out in the ductwork and affect the overall efficiency
of the system;
• The actual duct velocity required can be determined by considering the nature of the particles
that the system is handling such as size and density;
(c) To measure TV:
- A thermal anemometer (hot wire anemometer) - more suitable if air velocity in the duct is relatively low (less than 3ms-2 ) works by measuring the cooling effect of the air flow on a heated wire filament.
- A pitot-static tube – used for higher duct velocities; uses a pressure gauge (manometer) to measure velocity pressure, which can then be converted to duct velocity (m/s).
- The above measuring devices are introduced through a suitable sampling point and placed in the centre of the ducts air stream where there is laminar flow.
- Use U shaped manometer tubes that are placed strategically along the LEV duct system. They measure velocity pressure and these values can be converted to pressure velocity which is the transport velocity.
- Use a diaphragm gauge which gives a dial reading as a result of direct pressure to the diaphragm.
- Measure the speed of rotation of the extraction fan to calculate the theoretical duct/transport velocity. Although the actual air flow in the duct can be different if there are blockages.
Jul 11 Jan 10 Jan 08
A large manufacturer uses hydrochloric acid in a large open tank to remove rust from sheet steel. This creates acid mist in the immediate work area and the company has decided to install a local exhaust ventilation (LEV) system. This system consists of an inlet, ducting, air cleaner, air mover and exhaust.
(a) For each of the components listed above outline the design features required for the LEV system to be effective. (10)
(b) Explain the requirements of the Control of Substances Hazardous to Health (COSHH) Regulations 2002 for inspection and testing of the LEV system. (3)
(c) The LEV system breaks down and will take a number of weeks to repair. In the meantime the employees will need to use respiratory protective equipment (RPE) to control their exposure to the acid mist.
Outline factors to be considered when selecting the RPE to protect employees whilst engineers are repairing the LEV system. (7)
(a) Design features of
(i) Inlet hood / canopy - to be of adequate size / dimensions / area to capture acid mist from tank; adequate capture velocity and face velocity to ensure capture of mist; corrosion resistant (high grade stainless steel / acid-resistant polypropylene).
(ii) Ducting - to be of appropriate dimensions to transport volume of air; radius of bends to allow free flow and maintain “transport velocity”; duct junctions to be merged so as to reduce turbulence (simple sketch?); means of access to allow test / inspection - eg pitot tube holes pre-drilled; corrosion resistant as above.
(iii) Filter / air cleaning device - likely to involve neutralisation of acid mist by wet methods or contact with solid eg bicarbonate (alkali scrubber); (not bag filters = dusts / particulates).
(iv) Air mover / fan - to be of appropriate power to maintain capture velocity / face velocity / transport velocity / pressure drop across the system; axial or centrifugal type; corrosion resistant; low noise.
(v) Exhaust outlet sited to avoid nuisance eg odours / noise; protected from weather / cowl to reduce turbulence / “blowback”; baffles to prevent entry of vermin / birds nests etc.
(b) Reg 9 COSHH requires test and inspection of LEV system by a competent person at least once every 14 months - more often where specified in COSHH Schedule 4. Records to be kept for 5 years from date of test.
(c)
• full face or half mask;
• the protection factor required;
• the selection of the correct cartridges with respect to the acid mist and the battery life of the
chosen equipment;
• the degree of movement required by the wearer;
• their work rate of the user;
• the compatibility with other personal protective equipment such as eye protection;
• the comfort factor;
• Cost of maintenance and storage;
• Cost of training for the user;
• Cost of fit testing for close fitting respirators;
Jul 10 Jul 09 Jan 07 Jan 06
Employees of a landscaping contractor regularly cut kerb stones using a powered circular saw. This task requires the use of PPE to protect against the hazards associated with handling and cutting stone.
(a) For each type of PPE that should be used, outline the reasons why these items of PPE are needed. (6)
(b) Assuming that suitable PPE has been selected, outline a range of practical measures that can be taken to ensure the correct use of the PPE and to maintain its effectiveness. (4)
(a)
• hearing protection – the process is likely to cause excessive amounts of noise above action levels
• respiratory protective equipment – the cutting is likely to cause a significant amount of dust which could be inhaled
• steel toe capped boots – the saw itself or parts of the kerb stone could fall onto the feet causing a crush injury.
• eye protection – debris during the cutting process could cause a puncture injury.
• gloves – handling the kerb stone could cause a cut or abrasion injury
(b)
• Give information on the risks associated with the work they carry out and how the equipment will give protection against these risks;
• Give training on the correct method for putting on and fitting the equipment, how to remove it without contaminating themselves, how to recognise defects and damage, how to obtain replacements when needed and where and how to store the equipment when it is not in use.
• Management and supervision should wear the PPE themselves to set a good example;
Jan 10
A welder undertakes work in an open plan workshop.
Outline the factors to be considered when selecting suitable respiratory protective equipment for this work. (10)
(a) Factors to consider in the selection of RPE include:
- the nature of the hazard to health - metal fume / particulate - toxic, irritant etc
- the volatility of the consumables; concentration in air; particle size - the WEL
- whether half-face, full-face or BA is required
- if filtering face piece - the type of filter required
- the APF required to meet the WEL - the nature of the task
- duration of use
- frequency of use
- location in the workplace (sources of natural ventilation etc?)
- CE marking / manufactured to an approved design standard
- the need for the RPE to be compatible with other PPE / clothing
- the need to provide a range of sizes - fit / comfort (facial hair / spectacles)
- the comfort of the user
- levels of exertion
- need for dexterity and manoeuvrability and communication
- heat resistance of the RPE
- health / fitness of the user (heart strain etc)
- battery life
- need to ensure RPE does not introduce additional risk - see above + allergies etc - cost
- maintenance requirements
- training requirements
Jan 07 ****
An airborne contaminant has a Workplace Exposure Limit (WEL) of 40ppm, 8 hour time-weighted average (TWA). Despite the introduction of a range of engineering controls the airborne concentration of this contaminant in a workshop has been measured and has been found to be 160ppm, 8 hour TWA. The local manager has chosen a piece of respiratory protective equipment (RPE) with an assigned protection factor (APF) of 40 to be worn by all employees in the contaminated area.
(a) Using the data above explain how you determine if the manager has made an appropriate choice of RPE. (4)
(b) Suggest other factors that should be taken into account when selecting appropriate RPE. (6)
(a)
• APF is the concentration of contaminant in the air divided by the maximum allowed concentration in the face piece.
• In the scenario described, the maximum concentration in the face piece to which an employee should be exposed would be the WEL – 40ppm.
• Therefore, the minimum APF required would be 160/40 = 4.
• The actual APF is ten times the minimum and consequently the respiratory protective
equipment chosen would have a large safety factor and should offer a good level of protection.
(b)
• the nature of the dust or vapour involved;
• the length of time that employees would need to wear the equipment;
• the type of work to be carried out taking into account its physical nature, the degree of
movement required and the restrictions of the working space;
• the compatibility with other PPE;
• the ease with which it can be put on and maintained;
• its manufacture to an appropriate standard;
• the need to consult fully with the workforce on the selection of the equipment.
Jan 06
A slightly corrosive solution is used as part of a manufacturing process. The solution is applied by hand brushing. Alternative methods of application have been found to be impracticable.
(a) Outline the factors that should be considered in the selection of PPE (the PPE should ensure that the skin and the eyes of those involved in the process are adequately protected). (10)
(b) Identify the content of a training programme that will assist employees to use the PPE safely. (5)
(c) List a range of practical measures (other than training), that can be taken to encourage the use of the PPE and maintain its effectiveness. (5)
(a) Factors to consider in the selection of PPE include: - requirements of PPE regs - in particular:
Gloves
• Chemical resistance to the corrosive solution;
• Chemical breakthrough time;
• Level of dexterity required for the task;
• Length of the glove to afford adequate protection;
• Durability of the gloves;
• Suitable range of sizes should be available for the various users;
• Allergies to the glove material or any other skin problems;
Eye protection
• The risk of splashing the face as well as eyes;
• The use of goggles or a face shield with the appropriate level of chemical resistance and not
glasses;
• Compatibility with other protective equipment if this was required;
Body protection
• Aprons and/or overalls;
• Appropriate footwear - chemical resistance;
General factors
• Consultation and user trials;
• Comfort;
• British standards;
• CE mark.
(b)
• Health risks of the chemical in use;
• Type of personal protection to be used and the reason for its use;
• Methods for putting on and taking off the equipment without causing contamination including
decontaminating or discarding gloves after use;
• Methods of examining the equipment for damage - particularly gloves;
• Method of reporting defects and obtaining replacements;
• How to store the equipment correctly;
• How to carry out self-examination of the skin and the action to be taken if problems were to
occur.
(c)
• 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 maintain records of issue;
• Issue the equipment on a personal basis and provide adequate storage facilities;
• Use propaganda - signs and posters and incentive schemes;
• Monitor compliance in the use of the equipment with a recognised code of discipline for non-
use;
• Monitor the effectiveness of the equipment issued and replacing it with an alternative type if
problems were encountered.
Jul 05
In relation to respiratory protection equipment (RPE):
(a) Explain the meaning of `assigned protection factor’ (apf). (4)
(b) Calculate the minimum apf value for RPE required to provide protection against an airborne contaminant that has a concentration in the air of 15 mg.m-3 and an exposure standard of 0.1mg m-3 (2)
(c) Explain why exposure levels to an airborne contaminant may be higher in practice than those theoretically obtained by the application of an “apf”. (14)
(a)
• the ratio between the concentration of the contaminant in the air and the concentration within the face-piece when the RPE is worn;
• the data is derived from a survey of 10 subjects wearing RPE under laboratory conditions;
• the figures are published by RPE manufacturers to give an indication of the protection
achieved.
(b)15 mg.m-3 in the air outside the face piece must be reduced to 0.1 mg.m-3 inside.
To achieve this requires an apf of 150 (ie “outside”/ “inside” = 15 / 0.1 = 150).
(c) Exposure tends to be higher than that predicted in theory from the apf data because of:
• the lack of seal of the RPE to the face, because of;
o perspiration;
o facial hair;
o face movements during work; o ‘unusual’ face contours;
o incompatibility with other PPE.
• inadequate user training;
• contamination of the RPE during storage, fitting and removal;
• poor maintenance of the RPE;
• failure to replace damaged or worn parts;
• removal of the RPE for even short periods of time (poor supervision or misuse of the
equipment);
• Workplace conditions would be different from those in the laboratory where the apf value was
determined.
