B3 Exam Q's Flashcards
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 marks
Factors relating to the individual, task and substance that should be considered include:
the type, duration and frequency of the work and its position in the workplace
the fume control measures currently in place such as general or local exhaust ventilation
the health hazard category of the welding fume for example whether toxic or irritant
the level of protection (protection factor) required for each substance based on
considerations such as the amount of the substance, the volatility of the welding
consumables, the concentration and particle size and the relevant workplace exposure
limits (WELs)
the choice of the equipment in relation to the protection factor whether half face, full face
or forced air breathing apparatus
the choice of the correct filter type based on the determined protection factor
task related factors such as the work rate and wear time, the presence of humidity, the
need for mobility and communication and the amount of physical effort and degree of
movement required to carry out the task
the fit and comfort of the equipment taking into account facial hair and the need to wear
spectacles
the compatibility of the equipment with other personal protective equipment such as eye,
head or hearing protection
the heat resistant properties of the equipment
the battery life of specified types of equipment
the cost of the equipment and the amount of training and maintenance required for its
use
the manufacture of the equipment to recognised standards
any relevant medical conditions of the potential user such as heart disease, asthma or
claustrophobia.
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 and testing 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 marks
(b) In addition to these measurements outline other information that should be contained in the report. 16 marks
Measurements that should have been taken in examining and testing
the LEV system should have included:
the face velocity across the hood or opening
the capture velocity; the duct velocity
the pressure drop across the filter or fan
the static pressure in the hood or duct and the fan/motor speed
the power consumption
The report should additionally contain information such as:
The name and signature of the person carrying out the examination together with evidence
of their competence.
The date the examination was carried out together with the date of the previous
examination and test so that an assessment can be made as to whether the interval
between them was appropriate in accordance with the requirements of the COSHH
Regulations.
The location and extent of the LEV system being examined.
The process and hazardous substance it is intended to control.
A diagram of the layout of the system with the test points marked should be attached as should
also information on the system’s designed performance, its commissioned performance and that
noted at the last test.
As for the current test and examination, the report should:
note the conditions which appertained at the time, either normal or special
state the methodologies and equipment used to measure the performance of the system
such as, for example, anemometers, manometers or pitot tubes.
This will enable a decision to be made as to whether the methodologies used are in line with
those set out in the relevant HSE Guidance.
Other matters which should be addressed in the report include:
the calibration of the measuring equipment
a record of the actual measurements and observations made
results of any air sampling relevant to the performance of the LEV system or emissions to
atmosphere
details of adjustments or minor repairs made to improve the effectiveness of the system
and any remaining repairs or alterations that are required to restore its performance and
whether advice has been given to the recipient of the report that the record should be
maintained for a period of five years.
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. 4 marks
The concentration of contaminant in the air is 180ppm.
The WEL of 10ppm gives us the maximum concentration in the face piece that the
employee should be exposed to.
So, the minimum protection required (MPR) can be calculated as
180 \ 10 = 18
which means the minimum APF of the RPE for this situation is 18
The chosen piece of equipment has an APF of 20, which would, in-fact, lead to an
exposure within the face piece of
180 \ 20 = 9 ppm … lower than the WEL of 10ppm.
The chosen piece of equipment is therefore appropriate for use.
Note: A higher factor of safety could of course have been obtained by selecting respiratory protective equipment with an even higher APF.
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 marks
The hood would need to be of a suitable size to cover the tank and have a face
velocity adequate to capture the acid mist.
The ducting, because of the acidic nature of the contaminant, would have to be
corrosion resistant, be smooth with rounded bends, of size appropriate for the
required transport velocity and provided with access for testing and
maintenance.
The air cleaner would probably be by means of a wet scrubber, possibly in
combination with an alkali neutraliser, with appropriate means for disposing of
effluent.
The fan, either axial or centrifugal, would need to be corrosion resistant, of
sufficient power to provide the necessary extraction velocity and be designed to
minimise noise generation.
The exhaust outlet should be located following consideration of all
environmental implications including noise, should be corrosion resistant and
should be fitted with a weather cowl and deflector baffles to prevent the entry of
vermin.
(b) Explain the requirements of the Control of Substances Hazardous to Health (COSHH) Regulations 2002 for inspection and testing of the LEV system. 3 marks
A periodic visual inspection of a local exhaust ventilation system
together with a thorough examination and test must be carried out by
a competent person at least once in every period of fourteen months.
A record of the examinations must be kept available for at least five
years from the date on which they were carried out.
(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 the employees whilst engineers are repairing the LEV system.
7
marks
Factors to be considered in the selection of the equipment would be:
its type either 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.
Task related factors would also be important such as:
the degree of movement required by the wearer
their work rate
the compatibility of the respirators with other personal protective
equipment such as eye protection
the comfort factor.
Cost factors would also have to be considered such as those involved
in the maintenance and storage of the equipment and that which
would be necessary to provide training for the user in fit testing for
close fitting respirators.
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 marks
(b) Outline the arrangements the grounds maintenance contractor should put in place when the selected eye protection is in use. 3 marks
In carrying out the task described, the probability would be that impact might come
from a variety of directions and as a consequence goggles or a face shield should
be selected as eye protection. They would need to:
have good mechanical and impact strength
be shatterproof with medium energy impact
be adjustable to allow appropriate fit and comfort
be compatible with other personal protective equipment such as hearing, head
or respiratory protection.
Other possible features to be considered would be:
the optical class of the lenses
their resistance to misting and surface damage
the resistance of the frames to dusts.
Finally the protection should be CE marked and comply with a recognised standard.
Arrangements should be made for:
the provision of training in its use and its correct fitting with other equipment
the cleaning and storage of the equipment
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.
A local exhaust ventilation (LEV) system is used to
reduce exposure of workers to dust in the workplace.
(a) Identify THREE visual inspection methods that could be used to give a simple qualitative assessment of the effectiveness of the LEV system. 3 marks
Suitable methods included:
the use of equipment such as a Tyndall beam (dust lamp)
the use of smoke from pellets, tubes or generators
observations on the build of dust on surfaces in the workplace.
(b) Transport velocity is one of the quantitative measurements undertaken to assess the performance of the LEV system. (i) Outline why transport velocity is an important parameter to measure when assessing the effectiveness of the LEV system. 2 marks
(i) Transport velocity is an important parameter because an insufficient
transport velocity can result in dust particles settling in the duct and
lead to a blockage of the duct. As well as reducing the overall
efficiency of the LEV system, there is an increased fire or explosion
risk.
(ii) Outline the methods that can be used to measure transport velocity in a LEV system. 5 marks
(ii) Methods that could be used to measure transport velocity include:
A thermal or hot-wire anemometer, which consists of an
electrically heated wire exposed to the air stream (carrying the
particles) through the duct. The speed of the air stream affects the
rate at which the wire loses heat. Typically, the speed/velocity is
determined by measuring the electrical current necessary to maintain
the wire at a constant temperature.
A pitot-static tube (attached to a pressure gauge) detects airspeed
by placing a hollow tube into the air stream. As air jams into the end
of the tube, it creates pressure. By comparing the pressure inside the
tube with the natural pressure of the air around the tube (the static
pressure), you get an accurate measure of airspeed.
(b) Outline other factors that should be taken into account when selecting appropriate RPE. 6 marks
Other factors include:
the nature of the dust or vapour involved
comfort factors such as the length of time that employees would
need to wear the equipment and 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
whether fit testing would be required, the ease with which the
equipment can be put on and the amount of training required
the manufacture of the equipment to an appropriate standard and
its cost and durability
the ease of maintenance for example for cleaning and changing
filters
its compatibility with other forms of personal protective equipment
the need to consult fully with the workforce on the selection of the
equipment.
