July 2016 Question 8 In a chemical process, workers use a mixture composed of several liquid
substances. One of the components, designated DTJH, is classified as a sensitiser under the GHS
system. Table 1 below shows the average personal exposure levels to DTJH for one worker
measured over an 8- hour day and Table 2 shows the exposure limits for DTJH.
(a) Outline the process
of hazard classification
under the GHS system.
(2)
(b) Outline what is
meant by ‘sensitiser’
under the GHS system.
(4)
(c) Using the
information in Table 1,
calculate the 8-hour
timeweighted average
(TWA) exposure of the worker to DTJH. (6)
Your answer should include detailed working to show that you understand how the exposure is
determined.
(d) Using relevant information from Tables 1 and 2, explain what actions might be required by
the employer to control exposure. (8)
January 2017 Question 3 The hazardous substance called machine-made mineral fibre (MMMF)
has a legally binding occupational exposure limit (OEL) listed in standards. Unusually, there are
two OELs. The limit is expressed both as fibre/ml and also as mg/m3: 2 fibre/ml 8-hour time-
weighted average (TWA); 5 mg/m3 8-hour TWA). Two personal monitoring results, obtained
using two different measuring techniques for an operative working with MMMF, are provided
below:
Note:
1000ml = 1 litre
1000 litres = 1m3
(a) Calculate the average concentration of MMMF to which the operative is exposed for EACH
of the two samples shown. (6)
You must show your working.
(b) Comment on the significance of the operative’s exposure in terms of future action required
to adequately control exposure. (4)
Assume the exposure in the time monitored is representative of exposure during the full 8-hour
shift.
January 2017 Question 6 Dilution ventilation is sometimes 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.
(3)
(b) Explain how an effective dilution ventilation system is designed and operates to reduce
exposure to a hazardous substance. (4)
(c) The following specification applies in an open-plan workshop:
Calculate the actual number of air changes per hour AND comment on the suitability of the
specified dilution ventilation system. (3)
July 2017 Question 8 An organisation uses rubber substances in its tyre manufacturing process. Rubber
process dust and rubber fumes are produced during the process and both are classified as carcinogenic.
The following legally enforceable long-term exposure limits (8-hour time weighted average
(TWA)) apply:
(a) Outline what is meant by inhalable dust. (2)
(b) Outline the equipment and method required for personal sampling of inhalable rubber dust.
(7)
(c) Calculate the 8-hour TWA exposure to the process operators from BOTH the rubber process
dust and the rubber fume. (6)
(d) Comment on the significance of your answers calculated in part (c) in terms of exposure and
possible future action. (5)
July 2017 Question 11 An employer has identified that workers are exposed to high noise levels
and has used the single number rating (SNR) method to select hearing protection, using the
information below.
(a) Using the data in the above table, calculate AND explain how to determine a realistic
estimate of the A-weighted sound pressure level entering the ear of the workers wearing this
hearing protection. (4)
(b) Comment on whether the attenuation that is provided by this hearing protection is
appropriate. (2)
(c) Identify TWO other methods that could be used to determine if the hearing protection
selected provides appropriate attenuation AND, for EACH of these methods, outline the data
required in order to be able to calculate the attenuation provided by this hearing protection. (6)
(d) Other than noise attenuation, outline factors that the employer should consider when
selecting hearing protection. (8)
July 2018 Question 8 (a) Explain when it might be necessary to use respiratory protective equipment
(RPE) as a control measure to help reduce exposure to a hazardous substance. (6)
Workers carrying out a task involving the corrosive vapour of ammonia have been provided
with RPE to protect them from exposure to ammonia by inhalation. The employer used the
following information to determine the selection of the RPE:
(b) Explain how the employer can use this information to determine if the choice of RPE is
appropriate. (4)
(c) Outline what an employer should consider when selecting RPE for this particular task. (10)
July 2018 Question 11 In a chemical process workers are exposed to two organic liquids. Table
1 below shows the average personal exposure levels to each of the organic liquids for one
worker measured over an 8-hour day.
(a) Using the information in Table 1, demonstrate that the 8-hour time-weighted average
(TWA) exposures of the worker to BOTH Liquid A and Liquid B are as shown in Table 2. (8)
Your answer should include detailed working to show how the exposure is calculated.
The exposure limits for the two liquids are as follows:
(b) Outline what actions the employer might need to take to control exposure to Liquid A,
which is an essential component of the chemical process. (7)
(c) Comment on the exposure to Liquid B. (1)
(d) There is a concern that exposure to a mixture of these two liquids might increase the risk to
workers.
Consider why this might be a valid concern. (4)
July 2019 Question 3 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) (i) Calculate the number of air changes per hour for a dilution ventilation system with the
following specification:
(ii) Comment on the effectiveness of the specified dilution ventilation system in controlling
exposure to a hazardous substance. (2)
January 2020 Question 7 Workers in a large manufacturing organisation are exposed to a solvent by
inhalation, throughout their 8-hour shift.
(a) (i) Use the data in the table below to calculate the 8-hour time-weighted average (TWA)
exposure to a solvent for a worker. Your answer should include the detail of calculation to show
your understanding of how the exposure is determined. (7)
(ii) The organisation decides to change the working patterns so that each worker does a single
task for a 12-hour shift. A worker is assigned to the task of charging the mixers for their 12-hour
shift. Within the shift, they are allowed two 45-minute breaks where their exposure is assumed
to be zero.
Using this information and the relevant data above, calculate the 8-hour TWA exposure for this
worker. (2)
(iii) Outline the legal implications of this change in the working pattern. (2)
(b) The occupational health department at the organisation needs to decide whether to carry
out health surveillance for workers exposed to this solvent.
(i) Outline the purposes of health surveillance. (4)
(ii) Identify ONE type of health surveillance that may be appropriate for the workers using this
solvent. (1)
(iii) Other than health surveillance, identify FOUR functions that may be carried out by an
occupational health service in a large manufacturing organisation. (4)
