F1000ResearchF1000Research2046-1402F1000 Research LimitedLondon, UK10.12688/f1000research.159905.1Research ArticleArticlesRisk assessment of ammonia leakage by fault tree analysis: Case study in the ice manufacture, Chonburi province
[version 1; peer review: 2 approved with reservations]
NakyaiTeeranunConceptualizationMethodologyWriting – Original Draft Preparationhttps://orcid.org/0009-0001-4937-21421PhatrabuddhaSujeeConceptualizationInvestigationMethodology2HomsriPatomphongConceptualizationInvestigationMethodologyResources1PhatrabuddhaNantapornConceptualizationMethodologyWriting – Review & Editinga1
Industrial Hygiene and Safety, Burapha University, Mueang Chonburi District, Chon Buri, Thailand
Process and Industrial Engineering, Mahanakorn University of Technology, Bangkok, Bangkok, Thailandnantapor@buu.ac.th
Ammonia leaks during ice production can have significant impacts on the health of workers, nearby communities, and the environment. Exposure to ammonia can lead to both acute and chronic adverse effects.
Methods
A basic cause analysis of ammonia leakage in an ice production facility in Chonburi Province was conducted using Fault Tree Analysis (FTA). Boolean algebra equations were applied to construct primary causes, define failure type, and establish prioritization. Risk assessment was performed based on the criteria established by the Department of Industrial Work, incorporating both likelihood and severity to determine the risk level.
Results
The results identified 22 potential scenarios that contributed to ammonia leakage. When prioritizing these scenarios, dust accumulation and clogging of the fan, uninsulated ammonia transport pipes, coil obstruction due to scale build-up, incorrect shaft bearing motor, and the use of non-heat-resistant lubricants were significant contributors. Risk assessment analysis indicated both moderate and high risk of ammonia leakage. The use of incorrect bearing and non-heat-resistant lubricant in pumps was identified as high-risk, with a score of 9.
Conclusions
To mitigate this risk, it is necessary to replace bearings with standard ones and use heat-resistant lubricants to prevent pump failure and reduce cooling inefficiencies, which could lead to ammonia leaks. Regular inspection and maintenance should also be implemented. Furthermore, it is essential to enhance workers’ skills and expertise through training and practice.
risk assessmentammoniafault tree analysisice manufacturingThis research project was supported by a grant (ID02/2566) from Public health, Burapha University, ThailandThis research project was supported by a grant (ID 02/2566) from the Public Health, Burapha University, Thailand .The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.1. Introduction
An analysis of chemical spill accidents in Thailand over the past five years (2017-2021) revealed a total of 237 incidents. These accidents resulted in 414 injuries and 25 deaths, with fire-related accidents being the most frequent, accounting for 49.37 % of all incidents.
1 In terms of chemical leaks, Chonburi was identified as the province with the second highest number of chemical accidents nationwide. The industry with the highest frequency of chemical accidents were ice manufacturing, frozen food production, and cold storage, respectively.
2–
4 These factories use ammonia at various stages of their cooling processes.
Ice production plants, in particular, use ammonia as a refrigerant because of its high efficiency and low cost compared to chlorofluorocarbon (CFC) refrigerants and its non-destructive impact on the ozone layer.
5 However, ammonia is classified as a hazardous substance and poses significant health and safety risks.
6 It is stored under pressure and is classified as Class 2.3, indicating both poisonous and corrosive.
7 Additionally, under Thailand’s Hazardous Substance Act 1992, ammonia is classified as a Type 3 hazardous substance. The primary health and safety risks of ammonia are outlined by its risk phrases: R10 (flammable), R23 (toxic if inhaled), R34 (causing burns), and R50 (highly toxic to aquatic life).
8
The most common causes of ammonia leaks include the use of equipment, such as damaged components (e.g., leaks in pipelines, joints, and valves), inadequate safety procedures, and lack of proper and continuous maintenance.
4 Ammonia can react with water and humidity inside a factory to produce ammonium hydroxide, which is highly corrosive to gas pipelines and valves, leading to ammonia leaks.
9 Additionally, improper storage of ammonia containers, such as failing to designate a specific chemical storage area without neglecting to post warning signs, can also contribute to leakage. Many ice factories are old and are often located in densely populated areas. Ammonia leakage, which is acutely toxic, poses a significant health risk to both employees and the surrounding community.
10 Ammonia exposure can cause eye irritation, conjunctivitis, tearing, eyelid twitching, and skin burns.
11 The inhalation of ammonia can result in headaches, excessive salivation, chest pain, loss of smell (anosmia), and sweating. Chronic exposure may lead to severe health consequences, including premature death.
12
An ammonia leak occurred on April 17, 2024, at approximately 11:40 p.m. inside the ice factory in Bang Lamung District, Chonburi Province, causing ammonia to leak into the surrounding communities. Many individuals experience symptoms such as throat, suffocation, and eye irritation. Governmental officers were able to control the situation by 2:55 a.m., with several workers and nearby residents being affected. On the day of the incident, a total of 63 patients were taken to the hospital, with 160 people affected by ammonia, including 9 in serious conditions.
13
Most ice factories are small operations with fewer than 50 workers, which means that occupational health and safety may not be systematically managed. As a result, safety oversight is often inadequate, with no specific supervisor, professional safety officers, or safety committees in places, as per the Labor Law of 2022.
14 Therefore, the purpose of this study is to analyze the root causes of ammonia leakage in an ice factory using Fault Tree Analysis (FTA) techniques. In the subsequent section, risk assessment is conducted based on the criteria established by the Department of Industrial Work, which serves as a guideline for developing control measures to prevent future chemical leak incidents.
2. Methods
The research team collaborated with industry representatives to investigate the cause of an ammonia leak at an ice factory in Chonburi Province. On May 14, 2024, the team conducted interviews with ice factory executives and administered a survey. The collected data were subsequently used to write a report and perform a Fault Tree Analysis (FTA). This research is a survey-based study that utilizes event analysis through a top-down approach, following deductive logic. The analysis begins with the first event (Top Event), and subsequently identifies the causes at the next level of sub-events (Intermediate Event). The process continues until the root cause of the sub-event (Basic Event) is identified, which typically results from the machinery or equipment failure or human errors . The research employs tree chart analysis techniques in accordance with the regulations of Department of Industrial Work, focusing on the criteria for hazard identification, risk assessment, and risk management outlined in the B.E. 2543 (2000) plan.
15
2.1 Data collection and analysis
The initial or top event was defined as an ammonia leak in Bang Lamung District, Chonburi Province.
A fault tree analysis was conducted to identify the causes, starting with the initial event, and to systematically analyze the contributing factors. The analysis followed the symbols and guidelines outlined by the Department of Industrial Work (2000) as detailed in
Table 1. This process continued until the root cause (basic event) was identified.
The root cause of the problem was determined by assigning symbols to each gate and eliminating duplicate basic events using Boolean Algebra’s law.
The identified problem or root cause were then prioritized.
After the prioritization, the risk assessment considers both the probability of hazard and their severity through hazard identification. The probability of events is classified into four levels based on their frequency of occurrence, as shown in
Table 2. The severity of impacts on people, the community, property and the environment is outlined in
Table 3. The risk level is determined by multiplying the probability level by the severity level. In case where the severity affects different factors (people, the community, property, and environment) at varying levels, the highest severity level should be selected. The risk level can then be classified into fours level, as detailed in
Table 4.
Symbols used in risk assessment by FTA techniques.
<sup>
<xref ref-type="bibr" rid="ref16">16</xref>
</sup>
Event symbols
Name
Description
And Gate
Events occur because of the causes of every sub-event
Or Gate
An event can occur due to any one of the sub-causes
Basic Event
Events can happen normally. There is no need to do a root cause analysis
Fault Tree Event
Sub-events that result in a chain of events until causing an accident
Underdeveloped Event
An event that does not require further analysis to find the cause because there is no supporting information
External Event
External events or external factors that cause various events
Probability level of event.
Level
Description
1
Low chance of occurrence, unlikely to occur within 1 year or more
2
Low chance of occurrence, with a frequency of 1 time within 6 months to 1 year
3
Moderate chance of occurrence, with a frequency of 1 time within 1-5 months
4
High chance of occurrence, with a frequency of more than 1 time per month
Severity ranking according to the criteria of the Department of Industrial Works.
Level
Severity
Description
People
Community
Environment
Property
1
Low
Minor injuries at first aid level
Minor impact on the surrounding community of the factories
Minor environment impact, controllable or resolvable
Minor property damage (less than 50,000 baht), controllable or resolvable
2
Medium
Injury requiring medical treatment
Impact on the surrounding community of the factory resolvable within 7 days or 1 week
Moderate environment impact resolvable within 7 days or 1 week
Moderate property damage allowing production to continue, with costs between 50,000 and 100,000 baht
3
High
Serious injury or illness.
Impacting surrounding community of the factory resolvable within 7 to 14 days
Severe environment impact, requiring control or resolution within 7 to 30 days
Massive property damage necessitating the shutdown of operational units, with costs between 100,000 and 200,000 baht
4
Extreme
Disabled or dead
Severe impact on the surrounding community and large area, required government assistance for more than 1 month
Extreme environmental impact, requiring extensive time and resources for control or resolution, exceeding 1 month
Extensive property damage halting all production, exceeding 200,000 baht
Risk level.
Level
Multiplication product
Description
1
1-2
Low risk
2
3-6
Acceptable risk, requiring revision of control measures
3
8-9
High risk, requiring action to reduce risk
4
12-16
Unacceptable risk, requiring a cessation of operations
2.2 Process description
In the ice cube production process, the first step involves passing raw water through the conditioning stage. Water is pumped from rivers or groundwater sources into sedimentation ponds. After sedimentation, the water filter and its conditions were adjusted. In the ice production unit, the conditioned water from the storage tank is transferred into template molds, which are maintained at a low temperature of approximately -4 to -8
oC. It takes approximately 48 h (2 days) for the entire volume to freeze into the ice cube. After this period, the water in the mold was completely frozen. To remove the ice, the mold was removed from the brine pond and submerged in water, causing the ice to adhere to the mold’s surface and melt slightly. This allows ice cubes to be released from the envelope. The ice cubes were stored in a cold room until they were ready for distribution or sale. The block flow diagram and cooling system process for producing ice cubes using ammonia are shown in
Figures 1 and
2, respectively.
Block flow diagram of ice production process.
The cooling system process for producing ice cubes.
3. Results and discussions3.1 Basic cause analysis of ammonia leakage
Figure 3 illustrates the analysis of an ammonia accident from an ice manufacturing facility located in Banglamung, Chonburi Province, using fault tree analysis (FTA). As shown in
Figure 3, the primary causes of ammonia leakage are failure of the evaporative condenser and human error. The evaporative condenser failure may result from a broken fan, damaged ammonia transport pipe, or low cooling water level. A broken fan could be caused by a malfunctioning fan motor or dust clogging of the system. Ammonia transport pipes may be damaged by factors such as pipe deterioration, inadequate insulation, material stress, or the use of non-standard pipes. A low coolant level is typically attributed to a non-working pump or clogged cooling pad. Pump failure can result from issues such as using the wrong type of motor shaft bearing, non-heat-resistant lubricants, broken copper coils, and lack of maintenance. Human error can also contribute to leaks, often owing to a shortage of skilled technicians and the absence of daily inspections. In addition, inappropriate environmental conditions, such as insufficient lighting, uneven walkways, and the lack of an inspection system, can worsen the problem. The primary cause of ammonia leakage was identified using Boolean principles, which are placed at the top of the diagram. Sub-events are represented by rectangles (labeled W
1 to W
9), while basic events are depicted by circles (labeled A-O).
Tree structure diagram illustrating of hazard identification using fault tree analysis (FTA) technique.
By substituting
Equation (1) with
Equations (2)–
(10), we obtained the value in
Equation (11). According to
Equation (12), ammonia leakage can occur in 22 scenarios in total.
3.2 Prioritization
The risk assessment of the underlying causes of ammonia leak in Chonburi Province, using the Department of Industrial Works criteria, should consider the basic cause collectively. The criteria for considering which cause is most likely to result in accidents prioritize accordingly. If contains only one event, the minimum cut set is considered before the set containing two or three events. If multiple sets have the same number of basic events, human error is prioritized first, followed by active equipment failure, and then passive equipment failure.
Table 5 summarizes the basic causes, number of events, and priorities. All 22 scenarios were ranked according to their level of importance. The scenarios ranked first in importance are 4,5,8, and 9; those ranked second are 1, 3, 6, 7, 10, and 11; those ranked third are 3, 13, 15, 16, 19, and 20; and those ranked fourth are 12, 14, 17, 18, 21 and 22, respectively.
The primary cause, type of failure, and priority.
Scenario
Primary cause
Failure type
Priority
Scenario
Primary cause
Failure type
Priority
1
A,L
P,H
2
12
A,M,N,O
P,P,A,H
4
2
B,L
A,H
1
13
B,M,N,O
A,A,A,H
3
3
C,L
P,H
2
14
C,M,N,O
P,P,A,H
4
4
D,L
A,H
1
15
D,M,N,O
A,A,A,H
3
5
E,L
A,H
1
16
E,M,N,O
A,A,A,H
3
6
F,L
P,H
2
17
F,M,N,O
P,P,A,H
4
7
G,L
P,H
2
18
G,M,N,O
P,P,A,H
4
8
H,L
A,H
1
19
H,M,N,O
A,A,A,H
3
9
I,L
A,H
1
20
I,M,N,O
A,A,A,H
3
10
J,L
P,H
2
21
J,M,N,O
P,P,A,H
4
11
K,L
P,H
2
22
K,M,N,O
P,P,A,H
4
3.3 Risk assessment
Risk assessment is a process that analyzes the factors considering the likelihood and severity.
The consideration of hazard likelihood involves identifying equipment failures and human errors in operation. For hazard severity, data from identification hazards are used to assess the severity level and to evaluate the potential impact on people, property, community, and the environment.
Table 6 presents the risk assessment and corresponding levels derived from the prioritization section. It was found that scenarios 2, 5, 8, and 9 exhibited the highest likelihood of occurrence, as these scenarios were anticipated to occur once every to 1-5 years. Conversely, scenarios 2 and 12 demonstrated the lowest likelihood, with occurrence expected once every five to ten years. For severity assessment, scenarios 4, 8, 9, and 12 showed the highest severity (level 3) because of their significant impact on worker injuries and severe illnesses, as well as their effects on the factory, property, environment, and interruptions in ice production. For scenarios 2 and 5, the severity is classified as moderate (level 2) because of the potential for worker injuries, which require a short time to mitigate their impact on the factory, community, property, and environment. Consequently, ice production can be continuous without significant interruption. The results from the risk assessment indicate that scenarios 8 and 9 are classified as high-risk levels, whereas scenarios 2,4, 5, and 12 are classified as moderate levels. According to the Department of Industrial Work regulation on hazard classification, risk assessment and management operations with high-risk levels must be halted for improvements and maintenance. As shown in
Table 3, the use of an improper bearing type and a lubricant lacking heat resistance necessitates the adoption of standard bearings in the pump and the application of heat-resistant lubricants to minimize pump damage and maintain adequate cooling levels. In addition, moderate-risk levels, such as accumulation of dust, absence of pipe insulation, and fouling of the evaporator cooling pad, should be addressed through inspection, cleaning, and maintenance every two months. Training and reskilling are required to enhance worker knowledge and expertise.
Suggestion and risk assessment of ammonia leak accident.
Scenario
Hazard or consequences
Preventive measures and control/suggestion
Risk assessment
Likelihood
Severity
Risk level
2
Accumulation of dust obstructing the fan functionality
Inspection and maintenance fan
Cleaning the fan bland every 2 months
3
2
6 (Moderate)
4
Absence of insulation pipe
Implementation of pipe insulation
Inspection every 2 months
2
3
6 (Moderate)
5
Fouling of the evaporators cooling pad
Inspection and maintenance
Cleaning the evaporator and cooling pad
3
2
6 (Moderate)
8
Utilization of an incorrect bearing type
Used the standard bearing
Assess the efficiency of bearing and pump
Inspection every 2 months
3
3
9 (High)
9
Used of a lubricant that lack heat resistant
Used heat-resistant lubricants
3
3
9 (High)
12
The worker lacks necessary knowledge and expertise
Provide training to worker
Training every 6 months
2
3
6 (Moderate)
4. Conclusion
The fault tree analysis was applied to identify the basic events of ammonia leakage during ice manufacturing, and a risk assessment was conducted. The conclusions of this study are as follows:
FTA identified 22 scenarios related to ammonia leakage. Among these, scenarios, 2,4,5,8, and 12 are prioritized as the most critical.
The risk assessment revealed that ammonia leakage from evaporative condenser failure, caused by the use of nonstandard bearings and improper lubricants, is classified as high-risk.
Additionally, fan failure and damage to ammonia transport pipes resulting from dust accumulation and the absence of pipe insulation, respectively, were identified as medium risks.
To address these high-risk issues, ice production equipment should be upgraded to meet standards and subjected to regular inspection and maintenance to prevent ammonia leakage.
Implementing safety training programs on the use, storage, packaging, and transport of ammonia, as well as proper equipment and operation in ice production, will help mitigate future ammonia leakage.
Ethics and consent
Ethical approval were not required. We would like to confirm that we have received written consent from the interviewees to provide information regarding the ammonia leak in the ice plant.
Data availabilityUnderlying data
Figshare: Risk assessment of ammonia leakage by fault tree analysis: Case study in the ice manufacture, Chonburi Province.
https://doi.org/10.6084/m9.figshare.27979271.
17
This project contains the following underlying data:
Underlying data.xlsx. (Causes of ammonia leaks and labels and equipment failure image)
Data are available under the terms of the
Creative Commons Attribution 4.0 International license (CC-BY 4.0).
Extended data
Figshare: Risk assessment of ammonia leakage by fault tree analysis: Case study in the ice manufacture, Chonburi Province.
https://doi.org/10.6084/m9.figshare.28068950.
17
This project contains the following extended data:
Extended data_Interview guides_English
Extended data_Interview guides_Thai
Data are available under the terms of the
Creative Commons Attribution 4.0 International license (CC-BY 4.0).
Acknowledgments
The author would like to thank the Faculty of Public Health, Burapha University, for the research fund.
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A Review of Safety Issues and Risk Assessment of Industrial Ammonia Refrigeration System.ACS Chem. Health Saf.2022;29(5):394–404.
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The Potential Impact Analysis of Ammonia Gas Leakage On Refrigeration System Using Aloha Software (Case Study At PT. Cahaya Gunung Foods).IOP Conf. Ser. Earth Environ. Sci.2020;448:012103.
10.1088/1755-1315/448/1/012103AnjanaNSAmarnathAHarindranathan NairMV:
Toxic hazards of ammonia release and population vulnerability assessment using geographical information system.J. Environ. Manag.2018;210:201–209.
2935311410.1016/j.jenvman.2018.01.021HuLNiuJWuW:
Quantitative analysis of toxicity risks in the operation of ammonia-fueled tugboats.Ocean Eng.2024;310:118759.
10.1016/j.oceaneng.2024.118759Department of Industrial Works, Ministry of Industry: Handbook for the Management of High Hazardous Chemicals: Ammonia.2010. Accessed June 15, 2024.
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Risk assessment of ammonia leakage by fault tree analysis: Case study in the ice manufacture, Chonburi province.[Dataset].
Figshare.2024.
10.6084/m9.figshare.2806895010.5256/f1000research.175697.r421536Reviewer response for version 1RahmahAnisa Ur1Refereehttps://orcid.org/0000-0002-0990-1660
Universitas Muhammadiyah Surakarta, Sukoharjo, Indonesia
Competing interests: No competing interests were disclosed.
The article presents its objectives and methodology clearly in structure, but the clarity and accuracy of presentation are only partial. The paper follows a logical sequence—introduction, methods, results, discussion, and conclusion—but several sections lack linguistic precision and depth of explanation. For instance, the description of the Fault Tree Analysis (FTA) and its integration with the risk assessment process is brief and at times ambiguous. The paper does not clearly explain how Boolean algebra was applied or how the top event probability was quantified, which limits reproducibility and technical accuracy. In the literature reviews section, authors include a range of relevant and recent sources (e.g., studies from 2020–2024 on ammonia risk, dispersion, and refrigeration system hazards). These citations demonstrate awareness of current developments in the field. However, key methodological references on FTA theory and quantitative risk assessment are missing, and the link between past research and the current study’s novelty is not well established. The introduction lacks a clear articulation of the research gap—why another FTA-based ammonia case study is needed when similar analyses already exist.
The study design is partly appropriate but technically limited. The article applies Boolean equations to identify the possible leakage scenarios, it does not include quantitative probabilities or failure data, which limits its predictive and analytical strength. The FTA is treated mainly as a qualitative cause–effect mapping tool, not as a quantitative reliability assessment. The authors also do not include the validation steps of the causes and also data sources for failure probabilities, since FTA used generally as qualitative tools not quantitative assessment. The combination of FTA with Department of Industrial Works risk criteria (likelihood × severity) is conceptually acceptable, but the transition from FTA findings to risk scoring is not clearly justified mathematically. The assignment of likelihood and severity levels appears expert-based rather than evidence-based. No discussion is provided on the uncertainty of the assumptions, human error estimation, or potential model limitations.
The article provides incomplete methodological detail, hence replication by others would be difficult. No information on data collection instruments (interview/survey questions) and no explanation of how event codes (A–O, W1–W9) were assigned. The authors may add a flowchart or stepwise methodology illustrating how field data → FTA diagram → Boolean equation → risk matrix. Include sample data (e.g., interview themes or equipment failure logs). Justification for risk scoring (was it based on DIW manual tables, expert consensus, or historical data?) should also provided. The human error identification method (currently oversimplified). Boolean equation
s are shown in articles but not interpreted step-by-step.
Statistical analysis, not applicable.
The authors have made the underlying and extended data publicly available through Figshare, as stated in the
Data Availability section of the article. Therefore, even though the method description is limited, the source data themselves are available and accessible, fulfilling the criterion for reproducibility in terms of data transparency.
The conclusions are generally consistent with the research finding, but are only partially supported by the results due to the limited depth of analysis. Hence, the discussion section should merge results and discussion with the analytical comparison to prior research
Is the work clearly and accurately presented and does it cite the current literature?
Partly
If applicable, is the statistical analysis and its interpretation appropriate?
Not applicable
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Is the study design appropriate and is the work technically sound?
Partly
Are the conclusions drawn adequately supported by the results?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
Partly
Reviewer Expertise:
Risk assessment
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.
10.5256/f1000research.175697.r367487Reviewer response for version 1KetsakornArroon1Referee
Thammasat University, Bangkok, Bangkok, Thailand
Competing interests: No competing interests were disclosed.
According to the title, the manuscript describes risk assessment by applying the fault tree analysis in the ice manufacturer in Chonburi province. Partly due to language issues, the manuscript is not easy to read and understand, especially regarding the fault tree analysis. It is unclear how to use both fault tree analysis and risk assessment. Why did the authors choose to use those tools? However, this study has many good and important aspects but the manuscript needs some major, but I view, very “do-able” revisions.
Title
Please remove one letter from the address for Bangkok.
Abstract
-
Introduction
Please update the accident statistics by 2024
Please support the ammonia leak accident at factory with citations or literature sources when elaborating the aspects. This is an important step to find out the gap of research.
What is the gap of research? Because FTA is a tool that is already used for accident analysis.
Please send the manuscript to a native speaker to check before submission.
What are the advantages and disadvantages of using FTA?
Why did the authors choose the fault tree analysis? Please provide supporting reasons.
Objective
-
Methods
What kind of risk assessment does this research provide? Probabilistic risk assessment or quantitative risk assessment
How do the authors or teams identify human errors because human error do not have the reliability. Please give me details.
Please add the citation in Table 2-4
Please add more details on how to calculate the top event or undesired event
How do the authors prove the FTA diagram? Please add the details
Please specify the key qualifications or experience of the FTA team.
Results
Please give an example of manual calculation for FTA including minimal cut set
Discussion
The results should be discussed in the FTA section and risk assessment.
The discussion part should not be written in duplicate with the results of the study.
Authors must first discuss the study's findings and then explain how the study's results are similar or different from other studies.
Conclusion
The conclusion should not be written in duplicate with the results of the study.
References
Harmonize format with F1000Research style requirements.
Is the work clearly and accurately presented and does it cite the current literature?
Partly
If applicable, is the statistical analysis and its interpretation appropriate?
Partly
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Is the study design appropriate and is the work technically sound?
Partly
Are the conclusions drawn adequately supported by the results?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
Partly
Reviewer Expertise:
Occupational health and safety
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.