An integrated holistic approach to health and safety in confined spaces

Accepted Manuscript An integrated holistic approach to health and safety in confined spaces Lucia Botti, Vincenzo Duraccio, Maria Grazia Gnoni, Cristina Mora PII:

S0950-4230(17)30256-5

DOI:

10.1016/j.jlp.2018.05.013

Reference:

JLPP 3705

To appear in:

Journal of Loss Prevention in the Process Industries

Received Date: 14 March 2017 Revised Date:

30 January 2018

Accepted Date: 22 May 2018

Please cite this article as: Botti, L., Duraccio, V., Gnoni, M.G., Mora, C., An integrated holistic approach to health and safety in confined spaces, Journal of Loss Prevention in the Process Industries (2018), doi: 10.1016/j.jlp.2018.05.013. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT An integrated holistic approach to health and safety in confined spaces

Abstract

Confined space work is a high-risk activity, posing a significant hazard for both workers and rescuers

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involved in the emergency response. Risks due to working in confined spaces can be extremely dangerous. The leading cause of accidents and fatalities in confined spaces is atmospheric condition. Further common causes are fire, explosion, ignition of flammable contaminants, spontaneous combustion and contact with temperature extremes. Although confined space work is a high-risk

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activity, few studies have been oriented aiming to define structured procedures or comprehensive tools to identify and manage the risks of work in confined space. An organized and reliable methodology to assess and control risks associated with working in confined spaces in the process industry is missing.

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The aim of this paper is to propose a structured procedure for analyzing and managing risks in confined spaces in the process industry. After a first literature review on the topic and an historical analysis on accidents in confined spaces, the authors conceptualize a framework to prevent and manage the risks from working in confined spaces. The tool collects the concepts and requirements from the fragmented regulations on safe work in confined spaces, aiming to support both the assessment and the risk management. Two test cases show the application of the proposed framework

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showing an ex-post analysis carried out on a real accident occurred during a task execution in a

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confined space and an ex-ante assessment for risk prevention.

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Keywords: Confined space; risk assessment; risk management; safety procedure; industrial safety; job hazard analysis. 1 Introduction

Every year, confined space work causes fatal accidents and injuries, despite the in force regulatory and standards on such activity. Confined spaces are defined as limited or restricted areas not designed for continuous occupancy where employees enter and perform a specific task. Examples of confined spaces include, but are not limited to tanks, vessels, silos and pipelines. The high risk of confined space work can lead to extremely dangerous situations. Several publications, reports and recent news describe the impact of such risks on workers’ safety and health, showing high accident rates and multiple-fatality incidents (Burlet-Vienney, Chinniah, Bahloul, & Roberge, 2015a; NIOSH, 1994; OSHA, 2017; Sahli & Armstrong, 1992; Wilson & Madison, 2008). Common causes of accident in confined spaces are fire, explosion, spontaneous combustion and contact with high temperature extremes (Botti, Ferrari, & Mora, 2017a; Riaz, Arslan, Kiani, & Azhar, 2014). As an example, in case

ACCEPTED MANUSCRIPT of fire in a storage tank, the hot smoky gases rising from the fire reach the upper part of the confined space, heating the upper surfaces. The smoke layer resulting from the fire and the hot surfaces of the tank radiate down to the lower part of the enclosure, hitting the worker inside the confined space. Experience shows that the activity of the victim within the space is a factor contributing to cause the unfortunate event. Furthermore, ex-post analysis of accidents in confined spaces has revealed that the victim causes the presence of toxic gas or oxygen deficiency in several accidents due to hazardous

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atmospheric conditions, while accidents with entrapment are typically due to the attempt to unclog an accumulated deposit of materials. Several phenomena occurring in confined space greatly enhance deflagration and detonation processes (Salzano, 2014; Salvado, Tavares, Teixeira-Dias, & Cardoso, 2017). A metal tank containing a flammable mixture is capable of generating over pressures of 7e10

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times the initial pressure (McAllister, Chen, & Fernandez-Pello, 2011). This is due to several reasons, such as turbulence inducing acoustic wave reverberations and continuous compression and heating of

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the unburned mixture occurring from the burned products (Kolbe, Simoes, & Salzano, 2017). Recent pilot projects have been developed focusing on the application of Internet of Things technologies for improving safety and emergency management in complex production systems (Elia & Gnoni 2013, Yang et al. 2013). Few applications have demonstrated the potential of such technologies for managing hazards in confined spaces. As an example, portable wireless gas detection systems provide real data on atmospheric conditions within the confined area, allowing a quicker and a more

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efficient emergency response by alerting workers and safety managers in the case of toxic or flammable gas detection. Riaz et al. (2014) have developed a Building Information Modeling (BIM) platform aiming to improve visualization for effective monitoring of confined spaces on construction sites. The platform adopts numerous sensors to monitor real-time temperature and oxygen values,

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sending alerts and notifications to the health and safety manager. Although confined space work is a high-risk activity, few studies have been oriented to define how to

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treat and manage the risks of work in confined space (Botti, Bragatto, Duraccio, Gnoni, & Mora, 2016; Botti, Duraccio, Gnoni, & Mora, 2015; Burlet-Vienney et al., 2015a). Standard job hazard analysis methods do not specifically address the complex risks of working within confined spaces. A structured comprehensive methodology to assess and control risks associated with working in confined spaces, based on confined space regulations and standards, is missing. Worldwide regulation and standardsetting efforts provide fragmented procedures and recommendations for safe confined space work. However, the recent statistics show that several fatal incidents still occur. This paper aims to contribute to such issue by introducing and testing a procedure, based on a holistic approach, for analyzing and managing risks in confined spaces. Following the structure of generic job hazard analysis defined by the Occupational Health and Safety Agency (OSHA 3071, 2002) , the proposed tool gathers the fragmented regulations on safety in confined spaces.

The remainder of this paper is asACCEPTED follows. AfterMANUSCRIPT the literature review and the legislative overview on the confined space regulations in Section 2, Section 3 describes an accident that involved two workers who perished into a confined space. Furthermore, a brief historical analysis investigates the major causes of accidents in confined spaces and the industries exposed to the risks associated with working in confined spaces. The proposed procedure for the prevention and management of risks in confined spaces is in Section 4, while two applications are in Section 5. Finally, Section 6 and Section 7 discuss

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the results of the case studies and provide the conclusions and the future developments of this research.

2 Literature Review

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Confined space work is a high-risk activity, posing a serious life-threatening hazard to the workers. Hazards in confined spaces are difficult to evaluate and manage, due to the complex characteristics of such particular work environments (Nano & Derudi, 2012). Both the features of the confined area and

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the characteristics of the performed task have direct impact on the overall risk level of a specific confined space activity.

Several accidents and injuries related to confined space work showed that workers access to confined areas without proper training and personal protective equipment, exposing themselves to high levels of hazards (Botti, Duraccio, Gnoni, & Mora, 2015). The lack of situation awareness is an underlying cause of human errors, especially when workers access to areas not designed for continuous occupancy

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as confined spaces. Rescue attempts in confined spaces are also hazardous situations, since emergency response is a low-frequency, high-risk operation. Rescuing a worker from a confined space is a time sensitive and technically challenging operation (Wilson, Madison, & Healy, 2012). Many would-be

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rescuers perish while trying to rescue a victim after a confined space accident. Experience and historical data on accidents in confined space show that a unplanned and hurriedly executed rescue increases the probability that would-be rescuers will become victims (Wilson & Madison, 2008).

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Would-be rescuers victims include trained fire-fighters and competent personnel who had years of experience in emergency response. However, first-responding firefighters are not trained or equipped to effect a confined space rescue (Wilson et al., 2012). Data and statistics reveal that the 60% of confined space fatalities in U.S. occur among would-be rescuers (NIOSH, 1986). The chain of wouldbe rescuer deaths is an on-going phenomenon globally challenging. The Canadian Centre for Occupational Health and Safety and the European Agency for Safety and Health at Work (EU-OSHA) state the same 60-percent statistic (Muncy, 2013). These data reveal a hidden phenomenon, i.e. both employers and workers fail to identify confined space work hazards (Burlet-Vienney, Chinniah, Bahloul, & Roberge, 2015b). In 2017, (Botti, Mora, & Ferrari, 2017b) developed the first version of a tool for the identification of confined spaces in industry. The aim was to realize an effective tool to prevent workers entry into high-risk confined spaces. The tool addresses workers during the complex

ACCEPTED MANUSCRIPT identification of high-risk confined spaces. Furthermore, the tool supports the mandatory risk assessment for confined spaces computing the risk index for the analyzed confined space and task. Despite the worldwide regulation and standard-setting efforts in outlining procedures and recommendations for safe confined space work, the recent statistics show that several fatal incidents still occur (Burlet-Vienney, Chinniah et al. 2014). Confined space work procedures are not internationally standardized. Industrialized countries adopt different approaches to address such issue.

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The local legislation in force reflects the local strategy for addressing the risk of confined space work. American standards and regulations define the confined space geometric characteristics, together with the guidelines for job hazard analysis, hazard elimination, and the procedures for safe confined space work. The U.S. legislation widely investigates the risk of activities within confined spaces, providing

Table 1. Standards for work in confined space.

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the worldwide rules and standards con confined spaces.

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exhaustive guidelines and procedures for safe confined space work. Table 1 shows a brief overview of

Nation

Standard/Guideline

Field of intervention

USA

OSHA 1910.146 (1993)

Definition of confined space in general industry, requirements for practices and procedures to protect employees from the hazards of permit-required confined spaces.

Construction. Extension of the definition of confined space, including open top

(1987)

spaces more than 4 feet in depth.

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OSHA 1926.21(b)(6)(ii)

OSHA 29 CFR 1926 Subpart AA (2015)

OSHA 29 CFR 1910.272

Grain handling facilities.

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(1996)

Standard on confined spaces in construction.

Confined and enclosed spaces and other dangerous atmospheres in shipyard

Subpart B (2011)

employment.

OSHA 3138-01R (2004)

Informational booklet including a decision flow chart to help in identifying

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OSHA 29 CFR 1915

permit-required confined spaces and providing signage requirements.

OSHA 3071 (2002)

Requirements and guidelines for the job hazard analysis.

NIOSH 80-106 (1979)

Criteria for working in confined spaces, investigating the atmosphere characteristics of the confined areas.

NIOSH 86-110 (1986)

Case reports of fatal incidents concerning confined space work.

NIOSH 87-113 (1987)

Guidelines for safe confined space work.

NIOSH 94-103 (1994)

Data and investigative reports of fatal incidents involving workers who entered confined spaces.

ANSI/ISA 92.04.01 Part

Requirements for instruments used to provide a warning of the presence of

I-2007 (2007)

oxygen-deficient or oxygen-enriched atmospheres.

ANSI/ASSE

Z117.1-

Safety requirements to be followed while entering, exiting and working in

2009 (2009)

confined spaces at normal atmospheric pressure.

ASTM D4276-02 (2012)

Procedures to protect the health and safety of workers required to enter

confined spaces, and practice with specific safety steps to ACCEPTED MANUSCRIPT

be taken for entry

into confined spaces. UK

HSE (1997)

Requirements for safe confined space work. Apply where the assessment identifies risks of serious injury from work in confined spaces.

HSE (1999)

Require employers and self-employed people to identify the hazards present in confined spaces, assessing the risks and determining what precautions to take.

HSE (2014)

Approved Code of Practice (ACOP) and guidance for those involved in work

represent them. Swiss

SUVA 01416 (2004)

Guidelines for safe confined space work.

SUVA 44040.i (2010a)

Guidelines and checklist for maintenance activities in enclosed areas.

SUVA 44062.i (2010b)

Guidelines for activities in pits, sewers and pipelines.

SUVA

Checklists for inspection and maintenance in confined spaces.

CFSL:6806i

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(2012) SUVA 67103.i (2013)

Checklist for welding, cutting and other hot work.

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Regulation on occupational safety and health in general industry.

D.Lgs.

81/2008

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Italy

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within confined spaces, those who employ or train such people and those that

(2008) DPR 177/2011 (2011)

Requirements for confined space personnel and operating companies.

The 29 CFR 1910.146 (1993) standard of the American Occupational Health and Safety Administration (OSHA) is widely known as the Permit-Required Confined Spaces (PRCS) standard

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for confined space work in general industry. Such standard provides a general definition of “confined space”, together with requirements for practices and procedures to protect employees in general industry from the hazards of entry into permit-required confined spaces. The PRCS defines “Confined space” as a space that is large enough and configured that an employee can enter and perform work,

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has limited openings of entry or exit and is not designed for continuous occupancy (U.S. Department of Labor, Occupational Safety and Health Administration 1993). The OSHA 29 CFR 1910.146 is

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considered one of the most difficult OSHA’s standards to comprehend, likely is the hardest with which to comply (Taylor 2011). Confined spaces are not limited to enclosed spaces as storage tanks, process vessels, sewers and pipelines. The OSHA 1926.21 enlarges the definition of confined spaces. For purposes of such standard, confined or enclosed space means any space having a limited means of egress, which is subject to the accumulation of toxic or flammable contaminants or has an oxygen deficient atmosphere. Consequently, confined or enclosed spaces include open top spaces more than 4 feet in depth such as pits, tubs, vaults, and vessels. The 29 CFR 1910.146 protects employees who enter confined spaces while engaged in general industry work. This standard has not been extended to cover employees entering confined spaces while engaged in specific industries, as construction work or confined space workers in agriculture because of unique characteristics of such worksites. The US legislation provides precise standards for industries exempt form OSHA’s 29 CFR 1910.146, such as construction, agriculture and shipyard

ACCEPTED MANUSCRIPT work. For example, the OSHA 29 CFR 1926 Subpart AA (2015) protects construction workers in confined spaces, while the OSHA 1910.272 (1996) applies to grain handling facilities and the OSHA 29 CFR 1915 is for confined spaces in shipyard employment. Despite the numerous directions of the OSHA’s standards, employers in general industry have difficulty determining if spaces are permit-required confined spaces. The OSHA 3138-01R (2004) provides a decision flow chart to help identifying permit-required confined spaces and providing

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signage requirements. The main cause of accidents in confined spaces is the need of entering the high-risk area. The most effective risk control measure for work in confined space is not to enter the confined area. A recent study has collected innovative non-man entry technologies for work in confined spaces. The research

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focused on automated entry technologies for high-risk activities as cleaning, inspecting and maintenance (Botti et al., 2017a). However, effective and affordable non-man entry technologies are available for a limited number of industrial operations. Experience shows that several industrial

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applications require man entry into the confined space. When entry is not avoidable, organizations are required to perform a risk assessment. The US legislation explores the risk of confined space work from multiple perspectives, to help employers and employees in recognizing such hazardous workplaces. The risk of confined spaces is due to both the characteristics of the confined area and the characteristics of the task to be performed. Activities such as cleaning, repairing and welding can create a hazardous environment, when performed within the confined area.

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The American National Institute for Occupational Safety and Health (NIOSH) provides criteria and guidelines for preventing occupational fatalities in confined spaces (see in Table 1). The NIOSH publication 80-106 (1979) outlines a classification system for confined spaces, investigating the

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atmosphere characteristics of the confined area. The publication provides a checklist of factors to consider for the analysis of hazardous atmospheres, based on the content of oxygen, flammable substances and potential or toxic air contaminants. Further NIOSH publications provide guidelines for

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the recognition of confined spaces and their general physical hazards, together with statistics and findings on fatalities in confined spaces (NIOSH 1986, NIOSH 1987, NIOSH 1994). The American National Standard Institute (ANSI) and the American Society for Testing and Materials (ASTM) provide further standard practices for confined spaces and performance requirements for instruments used to detect the atmosphere of confined areas. A European Standard for confined space work is not yet available. The European Regulation on confined spaces is fragmented. The procedures and practices for safe confined space work apply to the country where the rules are published. The Britain legislation on confined spaces is based on The Management of Health and Safety at Work Regulations (1999) and the Confined Spaces Regulations (1997), which require workers to identify the hazards present, to assess the risks and to determine what precautions to take. The Swiss approach to confined space issues is based on the type of confined

ACCEPTED MANUSCRIPT space and activity to perform. The Swiss National Accident Insurance Fund (SUVA) provides several checklists for different confined space activities. Such checklists help confined space workers to analyze the hazard of typical confined spaces and activities to perform (SUVA 2004, SUVA 2010a, SUVA 2010b, SUVA 2012, SUVA 2013). The Italian legislation does not provide a specific regulation addressing the multiple risks of confined space work as it provides general requirements for work in polluted-suspected environments. Italian employers and employees are required to follow the

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directions of the TU D.Lgs. 81/2008 (2010), the Italian regulation on occupational safety and health. Such regulation provides requirements for occupational safety and risk assessment methods in general industry. The Italian specific rule for confined spaces defines the requirements for confined space

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personnel and operating companies, but no guidelines for safe confined space work are provided.

3 Accidents in confined spaces ACCEPTED MANUSCRIPT Incidents in confined spaces frequently lead to multiple fatalities as would-be rescuers perish while trying to rescue the first victim of the accident. Two major risks associated with working in confined spaces are asphyxiation and intoxication (Frensh ministry for sustainable development -SRT / BARPI, 2009). These risks are present in several sectors, e.g. chemical industry, agricultural industry, food processing and wastewater industry. Accidents in chemical processing and refining frequently

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implicate the introduction of nitrogen for inerting purposes or toxic gases (H2S, NH3, Cl2, etc.) used or released during the various processes. Specifically, gaseous releases might occur during process implementation.

Before introducing an historical analysis of accidents in confined spaces, this section describes a tragic

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event in which two workers were asphyxiated inside a nitrogen filled confined space in a U.S. refinery in 2005. The event is sadly known as the “Valero Refinery Asphyxiation Incident”. The workers were engaged in reinstalling a large pipe elbow on the top of a pressure vessel, called a

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hydrocracker reactor, during the overnight shift. The uninstalled pipe left an opening on a work platform 24 inches in diameter, surrounded by two-foot high steel bolts. The reactor was performing a purification process which removes oxygen and hazardous gas from equipment by flowing nitrogen through it. The investigations revealed that the workers decided to attempt to remove a roll of duct tape lying inside the reactor with a long wire hook. The roll was five feet below the opening. The workers repeated numerous attempts to remove the tape with no success. Investigators concluded that one

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worker stepped over the bolts and sat on the narrow ledge around the opening, to improve his chance

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of hooking and removing the tape.

Fig. 1. Reactor MANUSCRIPT opening (CSB, 2006). ACCEPTED

The worker intentionally entered or fell into the reactor, where the oxygen-depleted environment created by the nitrogen flow overcame him. He immediately collapsed. The second worker quickly inserted a ladder through the opening and climbed inside, trying to rescue the colleague. He too was overcome by the oxygen-depleted environment and also succumbed. The oxygen content in the

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atmosphere was less than one percent. Efforts by properly-equipped emergency responders to revive

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the men were unsuccessful and the men were declared dead at the hospital (CSB, 2006).

Fig. 2. Reactor work platform (CSB, 2006).

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The U.S. Chemical Safety Board (CSB) stated that the accident could have been avoided through better hazard awareness training and proper confined space rescue actions. The Valero incident shows that workers are not properly trained on the dangers of confined spaces in the complex plants of process industry. Nitrogen asphyxiation caused 80 deaths and 50 injuries in U.S. from 1992 to 2002

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(CSB, 2006).

ACCEPTED This section shows a quantitative analysis on MANUSCRIPT incidents in confined spaces, aiming to identify the major causes of accidents and fatalities. The main databases and archives collecting data on occupational safety have been verified to gather and analys accidents and fatalities due to work in confined space. Such databanks include the CSB, Facts (Failure and ACcidents Technical information System), the OSHA (US Occupational Safety and Health Administration), CRED (International Disaster Database), ARIA (Analysis, Recherche et Information sur les Accidents) and the NIOSH (The

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National Institute for Occupational Safety and Health) archives, which provided the most updated data on confined space fatalities. In particular, NIOSH data report that the total number of accidents in confined spaces in US between 1985 and 2015 was 141, which have caused 197 fatalities and a consequent average fatality rate per accident of 1.39 (NIOSH 2016).

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Data have been arranged in relation to the type of industry: chemical (e.g. accidents in reaction vessels), food (e.g. accidents in silos) and utility (e.g. accidents in sewers). Figure 3 shows the results of the accident analysis. Left side of Figure 3 (A) refers to NIOSH data (NIOSH 2016) while right side

A

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(B) shows Italian accidents in confined spaces by industry (Botti et al., 2015).

B

12%

Wastewater industry

Wastewater

19%

Chemical

29%

38%

15%

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Construction

Other Food industry

Mechanical

24%

10%

12%

Chemical industry

Other

15%

8%

Agricultural Pharmaceutical

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3% 15%

Agriculture

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Fig. 3. Classification of accidents in confined spaces by industry ( A: NIOSH data, B: Italian data).

Both US and Italian data in Figure 3 show that the highest number of accidents in confined spaces are in wastewater industry. The collection and treatment of industrial or agricultural wastes, in addition to their associated wastewater networks, causes the production of gaseous effluent by means of physicochemical reactions or fermentation (H2S). Furthermore, wastewater treatment technologies and plants are located below ground level. Workers enter into such confined areas by access stairways to perform routine maintenance, inspection, testing, sampling and repairing operations. NIOSH data (Figure 3A) revealed high prevalence of confined space fatalities in agriculture, i.e. farming activities use tanks and silos associated with the phenomena of normal or accidental evaporation or fermentation (e.g. CO, CH4, CO2, alcohol) of organic materials. The analysis of Italian data (Figure 3B) revealed a significant number of accidents in confined spaces in the food industry,

MANUSCRIPT that involved workers in storageACCEPTED tanks, grape presses, fermentation tanks, utility vaults and vessels. Accidents in food processing industries are due to intoxications from ammonia used in refrigeration installations, accidental mixes of incompatible chemical substances (e.g. acid and bleach) and fermentation phenomena (CH4, H2S, etc). Seven main causes of accident have been identified as asphyxiation, engulfment, poisoning, oxygen deficiency, drowning, explosion, and electrocution. Data classification is proposed in Figure 4.

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Specifically, when the total number of occurrence is less than 3, data have been grouped in the “Other” category. Results show that Asphyxiation is the most frequent cause of death when an accident in confined space occurs.

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100 90 80

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N° fatalites

70 60 50 40 30 20

0

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10 Asphyxiation Engulfment Poisoning

Oxygen deficiency

Drowning

Explosion

Other

Electrocution

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Fig. 4. NIOSH accidents classification based on causes and number of fatalities occurred in confined space from 1985 to 2015.

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These results confirm the statistics reported by Wilson, Madison & Healy (2012) on confined space emergency response. Italian statistics on accidents in confined spaces from 2001 to 2016 show similar results. Specifically, the total number of accidents in the analyzed period is equal to 20 accidents, which have caused 60 fatalities; in this case, the average fatality rate is equal to 2.25 fatalities per accident. Results are in the Figure 5.

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35 30

N° fatalites

25 20 15 10 5 Asphyxiation

Poisoning

Falling

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0 Explosion

Drowning

Fig. 5. Italian accidents classification based on causes and number of fatalities occurred in confined space from 2001 to

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2016.

Aiming to provide a reference tool for the prevention and management of the risks associated with

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working in a confined space, Section 4 introduces a procedure for safe work in confined space.

4 The procedure for safe work in confined space

Structured procedures and technical guidelines on risk assessment and management for confined space work are not standardized and not effectively integrated. Thus, a stepwise procedure for the prevention

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and management of confined spaces risks is now discussed in detail aiming to provide technicians, practitioners as well as researchers with a reliable tool for the analysis of the dangerous scenario in confined spaces. Specifically, the procedure consists of a framework that collects the concepts and requirements from the fragmented regulations for safe confined space work. The aim is to support both

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the assessment and the risk management phases.

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Fig. 6. The proposed framework

The stepwise approach in Figure 6 addresses safety managers and risk analysts during the design of work procedures and risk assessment for work in confined space. Firstly, the framework proposes the analysis of the characteristics of the confined area, the characteristics of the task and the requirements of the emergency response plan. Next, the overall risks that could affect a confined space work are analyzed in detail. The risk assessment includes the analysis of both the causes and the consequences of the activities performed within the confined area. The procedure terminates with the analysis of the engineering and administrative controls for risk elimination or reduction.

Phase 1: Analysis.

ACCEPTED MANUSCRIPT The first step of the procedure guides safety specialists and practitioners through the analysis of the confined space characteristics. The analysis investigates the characteristics of the confined space, the characteristics of the task and the requirements for safe emergency response in case of accident. The first analysis includes the analysis of the characteristics of the confined space. Both the geometric characteristics and the atmospheric characteristics of the confined space affect the safety conditions of the confined area. Particularly, confined spaces are restricted areas with limited openings for entry and

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exit. Consequently, the restricted airflow and the hazardous contents may determine atmospheric conditions immediately dangerous to life or health (OSHA 1993). The second analysis investigates the characteristics of the task performed in the confined space. Both the adopted equipment and the performed activity may affect the atmospheric conditions of the confined area and contaminate the

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atmosphere. Finally, the third analysis includes the study of the requirements for safe emergency and rescue operations. The emergency response plan analysis aims to ensure high performances of both the emergency response plan and the emergency and rescue procedures, in case of accident in the confined

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area. Particularly, the preplan of the confined space incident helps emergency response team in identifying the causes and the consequences of possible incidents. The analysis of emergency and response plan concludes with the preplan of the emergency and rescue operations. The aim is to identify an effective approach for confined space rescue operations. This phase involves the design of a standard emergency and rescue procedure, and the phases from the request for emergency response

Phase 2: Risk assessment

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to the termination of the emergency intervention (Hansen 1999).

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Risk identification and assessment for work in confined spaces are difficult and complex. The second step of the framework analyses the multiple risks of confined space work. The aim is to identify the leading causes of confined space incidents and the possible hazards in such workplaces. Three main

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types of risk characterize confined spaces: electrical, mechanical and chemical risk. Electric shock injuries and deaths are frequent consequence of electrocution in confined spaces. Mechanical risks include the risk of entrapment, asphyxiation and engulfment due to drowning or falling objects. Finally, hazardous atmospheric conditions lead to fire, explosion, poisoning and other hazardous consequences of the chemical risk in confined spaces. Other possible risks of work activity in confined spaces include temperature extremes, noise, vibration and communication problems (see Figure 6).

Phase 3: Risk elimination or reduction

The information obtained from the hazard analysis in Phase 1 and the risk assessment in Phase 2 allow to identify the control measures for risk prevention. The aim of Phase 3 is to define the control

ACCEPTED MANUSCRIPT methods to eliminate or to reduce the risks identified in the first two phases of the framework. The most effective control methods are engineering controls, which physically change the characteristics of the work activity preventing the exposure of the workers to the risks arising from work in confined space. Engineering controls for risk elimination are preferred control methods, rather than engineering controls for risk minimization, enclosure, isolation or redirection. Such control measures include the use of static electricity for the risk elimination or the use of continuous forced air ventilation for risk

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redirection (Garrison & Erig 1991). If engineering controls are not feasible, administrative controls may be appropriate. Such controls involve operating procedures or organizational methods, e.g. written operating procedures, safe work practices and training. Finally, PPE is an acceptable control method if engineering controls are not feasible or when administrative controls do not provide adequate

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additional protection. Safety plans and procedures may include engineering control methods rather than administrative controls or PPE, aiming to provide protection and to abate the hazards in confined

of all the three types of control method.

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spaces. If engineering controls can not eliminate the risk, the optimal control measure is a combination

Section 5 introduces the application of the proposed framework to two test cases. Specifically, the first test case shows data and information from the investigative report on a fatal accident involving an employee while he was working into a confined space. The second test case describes the manufacturing process of a metal tank and the phases in which the worker is required to enter into the

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tank.

5 Test of the proposed framework

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Two test cases are discussed to show the application of the framework described in previous Section 4. The aim is to validate the global effectiveness of the proposed tool by its application in two different case studies: an ex-post analysis carried out on a real accident occurred during a task execution in a

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confined space and an ex-ante assessment for risk prevention. 5.1 Test case 1: fatal incident in a tank This Section introduces summary data and investigative reports of a fatal accident involving a worker who entered an oil storage tank. Specifically, the following case study is from the NIOSH State Face Report (NIOSH 2014). The investigations revealed the wrong application of safety procedures during maintenance activity in an oil storage tank. The unsafe operations caused the death of a welder who was repairing the tank. The worker was inside the confined space to weld a defect that caused the oil leakage from the tank. After detecting the leak position, the site manager activated the procedure for the tank recovery. The recovery process included four different phases:

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MANUSCRIPT Aspiration of the liquids inACCEPTED the four tank compartments;

•

High pressure steam cleaning (90 minutes);

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Inspection of the tank (worker entry);

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Maintenance and repair operations inside the tank (worker entry).

During the first two phases, the welder prepared the welding equipment. A fan was introduced inside the damaged compartment of the tank to decrease the inner temperature. The welder entered the tank to

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set the fan when an explosion killed him instantly. The investigation reported the cause of the explosion as lack of refrigeration of the adjacent compartment. Consequently, the temperature increased triggering the residual vapours inside the tank.

The proposed framework suggests analysing the characteristics of the confined space and the task to be

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performed, aiming to identify and manage the risks of confined space work.

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Phase 1: Analysis.

The tank capacity is about 50,800 l, divided in four compartments of 15,990 l, 6,430 l, 9,460 l and 18,930 l. Four manholes (0.45 m diameter) allow the access to each compartment. Furthermore, each compartment is provided with an inspecting hatch (0.25 m diameter) on the top. Repair and maintenance are performed inside a building with four garage doors. The characteristics of the tank

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identify a confined space. Different maintenance operations may be performed. Welding tasks are performed with an MIG welding torch.

The first two phases of the recovery process (aspiration of residual liquids and high pressure steam

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cleaning) are completed outside the building (Figure 7) and prior to inspection.

Fig. 7. Oil storage tank (on the left) and the extractor fan (on the right) (Center for Disease Control and Prevention, 2015).

A metal canopy protects the tank outside the building (Figure 7). A supervisor oversees the whole recovery process and the actuation of each phase.

ACCEPTED MANUSCRIPT Phase 2: Risk assessment

The worker enters the tank to perform inspecting operations. During such activity, the tank can contain vapour and liquid residuals potentially harmful. These agents may cause worker asphyxiation. Furthermore, fumes and gas from welding operations may displace the oxygen in the tank to the extent

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that it will asphyxiate workers almost immediately. Finally, the high temperature inside the tank and the adoption of electric equipment (e.g., welding torch) expose the worker to the risk of explosion, fire, thermal shock and electrical shock.

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Phase 3: Risk elimination or reduction

The risk elimination or reduction is obtained through residuals aspiration and high pressure steam cleaning. In case of worker entry, an extractor fan is placed inside the tank (see Figure 7 on the right

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side). The extractor provides mechanical ventilation, refrigerates materials after steam cleaning and increases the air content inside the tank compartment. The investigative report showed that no preventive measures for explosion hazard triggering were taken. Internal procedures require the adoption of air monitoring equipment inside the tank. Such tool was not available when the accident occurred. Further possible risks concerning electrocution have been considered. The accident and the related investigative reports have shown lack of confined space risk management.

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The company did not include the recovery operation among the activities performed in confined space. No documents described the operations performed by the workers and no air monitoring equipment was available during the operations. Finally, workers were not prepared to work in confined space.

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Consequently, specific safety procedures and operations for safe confined space work were omitted.

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The result was the explosion of the tank (Figure 8).

Fig. 8. Tank conditions after the explosion (Center for Disease Control and Prevention, 2015).

ACCEPTED MANUSCRIPT 5.2 Test case 2: metal tank manufacturing process This Section shows an application of the proposed procedure to a test case concerning the manufacturing process of a big-sized metal tank (Figure 9). The tank is included in the filtration process for the treatment of potable water. Once the treatment system is in service, raw water goes

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through the filtering layers contained within the tank.

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Fig. 9. Metal tank for water treatment (on the left side) and worker entry into the metal tank (on the right side).

The tank manufacturing process requires a worker to enter a cylindrical tank to perform welding of the metal components of the tank (e.g. top, lateral metal sheet, bottom and other small components). Specifically, the worker accesses inside the confined space twice for performing welding operations

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(see Figure 9 right side).

Following the step-wise procedure of the framework in Figure 6, the characteristics of the tank and the

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characteristics of the welding operations are analysed to identify the risks of the introduced confined space work and the risk control measures to adopt.

Phase 1: Analysis.

The tank diameter is 3 m. During welding operations, a positioning device sustains the tank with the diameter perpendicular to the floor, as in Figure 9. The width of the internal space where worker welds components is about 1.3 m, while the height is 3 m (tank diameter). The worker accesses the tank through a manhole of DN 500. The manhole is the same for both the entry and the exit. Such features identify a condition of high confinement for both the confined space and the access. An additional opening is positioned on the top of the tank. The dimensions are 420 x 320 mm. The airflow is restricted.

ACCEPTED MANUSCRIPT The welder performs welding operations by means of a welding torch. A pipe positioned on the additional opening is connected to an artificial ventilation system to suck the welding fumes. The temperature inside the tank and close to the welding point is about 40°C. The worker keeps a kneeling or crouching position for the whole duration of the welding operations. Specifically, the welding task inside the confined space requires up to 45 minutes. The worker accesses the confined space wearing proper protections (e.g., gloves, leather clothes, mask, kneepads and ear plugs) and equipment to

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monitor the atmosphere (e.g. portable multi gas detector). A second worker, the attendant (OSHA, 1993), is stationed outside the tank, monitoring the entrant and the position of the pipe connected to the ventilation system. The victim removal equipment is a pulley arranged on a removable metal base. The connections on the ground for the installation of the metal base are arranged close to the point

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where the worker accesses the tank. During the welding operations, the pulley and the base are stored close to the tank. In case of emergency, the attendant retrieves the rescue equipment and fixes the rescue equipment with the connections on the ground, hooks the worker inside the tank and pulls by

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means of the pulley.

Phase 2: Risk Assessment.

The welder assumes awkward and static postures for extended periods of time while welding. Consequently, welding inside the tank exposes the welder to ergonomic risk factors. Such conditions

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are associated with the development of work-related musculoskeletal injuries and disorders (Stack, Ostrom et al. 2016). Welding operations produce fumes and gases that could cause a reduction in the oxygen percentage content inside the tank and asphyxiate the worker. Furthermore, the high

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temperature inside the tank and the use of an electric device expose the welder to the risks of fire, explosions, thermal shock and electric shock.

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Phase 3: Risk Elimination or Reduction.

The complete elimination of the hazard is possible by preventing worker entry, as required by regulations on confined space work. Non-man entry technologies are automated solutions that replace the workers for activities in confined spaces. Examples of non-man entry technologies for welding operations in confined spaces are automated welding robots. Welding robots are widely adopted in industry. Such robots consist of a programmable manipulator arm equipped with welding automation equipment. The welding task is pre-programmed by the worker outside the confined area or guided by machine vision, or by a combination of the two methods. Either way, the welder is not required to enter the confined space and the risk of confined space work is eliminated. The adoption of written operating procedures and permits for work in confined space are further effective risk control methods.

MANUSCRIPT Specifically, the PRCS standard ACCEPTED defines “Permit-required confined space” a confined space that has one or more of the following characteristics: contains or has a potential to contain a hazardous atmosphere; contains a material that has the potential for engulfing an entrant; has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward and tapers to a smaller cross-section; or contains any other recognized serious safety or health hazard. The permit-to-work certificate identifies the tools allowed in the

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confined space and the requirements for work implementation. The issue of the permit ensures a safe atmosphere inside the confined space prior to entry and during work in progress. The validity of the permit is limited to the time stipulated on the certificate, after which workers are required to leave the confined space. Permit-to-work certificates and risk assessment reports should be accessible and

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visible within the immediate vicinity of the confined space. Leather and flame-resistant treated cotton clothing is recommended in welding environments, as they provide durability and fire resistance. PPE protect welding operators from injury, such as burns, which are the most common welding injury. The

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use of hearing devices and protective gloves reduces the exposure of the worker to noise and to the risk of electrocution. Furthermore, the welder should wear a respiratory mask for welding operations, provided with a self contained breathing apparatus. Finally, proper and adequate PPE allow freedom of movement while providing sufficient protection from welding hazards.

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6 Discussion

This paper has conceptualized a procedure for preventing and managing confined space risks. Although confined space work is a high-risk activity, few studies and technical reports have been

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oriented to define how to treat and manage the risks of work in confined space. Regulations on occupational safety and health provide directions and stepwise procedures to identify hazards before they occur and to eliminate or reduce them to an acceptable risk level. As an example, the OSHA 3071

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(2002) Standard proposes a stepwise procedure for the job hazard analysis in general occupational worplaces: task description, hazard description and hazard controls. After reviewing the task characteristics and the types of hazard, the procedure considers the control methods for the elimination or the reduction of the identified hazards. Control methods include engineering controls, administrative controls and Personal Protective Equipment (PPE), such as respirators and protective clothing. Engineering controls physically change a machine or work environment to prevent employee exposure to the hazard. If engineering controls are not feasible, the OSHA 3071 encourages the adoption of administrative controls, e.g. written operating procedures, work permits, and safe work practices. Finally, PPE is an acceptable control method when engineering controls do not totally eliminate the hazard or when safe work practices do not provide sufficient additional protection.

ACCEPTED MANUSCRIPT Job hazard analysis aims to identify hazards before they occur, eliminating or reducing them to an acceptable risk level. However, a structured and reliable methodology to assess and control risks of confined space work is missing. Recent statistics on accidents in confined spaces has shown that, despite current job hazard analysis procedures and risk assessment methods, confined space fatalities still occur. Confined spaces regulations widely address the problem of safety and risks in confined spaces. Table 1 has provided a list of world-wide regulations on work in confined spaces.

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Previous studies have investigated the problem of safety in confined spaces, aiming to realize a comprehensive risk identification and to categorize interventions by means of checklists and questioners (Burlet-Vienney et al., 2015a). This paper has introduced a framework to address risks of confined space work adopting a holistic approach to safety in confined spaces. The aim is to help

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employers and safety professionals during the design of work activity in confined spaces, supporting the risk management and addressing critical aspects of safety in confined spaces. The proposed framework collects the concepts and requirements from the fragmented regulations for safe confined

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space work. As required from regulations on general job hazard analysis, risk analysis and risk assessment are addressed in the first step of the framework. Specifically, Step 1 includes the analysis of three critical aspects of safety in confined spaces, i.e. the characteristics of the area, the characteristics of the task and the analysis of the emergency response plan. Step 2 investigates causes and consequences of risks in confined spaces. Finally, the third step of the framework addresses the choice of engineering and administrative risk control measures, and PPE to eliminate or reduce the

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identified risks. The application of the proposed framework to two case studies from industry has proved its effectiveness in preventing hazardous situations and accidents in confined space.

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7 Conclusions

This paper has introduced a structured and effective procedure for risk assessment and risk

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management of work activity in confined spaces. Every year, this activity causes fatal accidents and injuries. Incidents in confined spaces frequently lead to multiple fatalities as would-be rescuers perish while trying to rescue the first victim of the accident. The results of historical analysis on accidents in confined spaces in Section 3 show that the major cause of fatalities in confined spaces is asphyxiation. Despite the rising accident rates and the statistics on multiple-fatality incidents, confined space work procedures are not internationally standardized. Industrialized countries adopt several standards, regulations and codes of practice on confined space work, based on their local legislation: a unified methodology to analyze and control the risks of confined space work is missing. This paper has introduced a structured procedure to address the risks associated with working in confined space. The procedure adopts a holistic approach to safety in confined spaces in the process industry. Specifically, the framework proposed in Section 4 gathers the directions and the guidelines from the fragmented

ACCEPTED MANUSCRIPT regulations, addressing safety managers and practitioners during the design of work procedures for safe work in confined spaces. Three phases define the structure of the framework: analysis, risk assessment, and risk elimination and reduction. The first phase includes the analysis of the characteristics of the confined area, the characteristics of the task and the characteristics of the emergency and response plan. The second phase investigates the causes and consequences of risks in confined spaces. Finally, the third phase analyses the risk control measures (e.g., engineering controls,

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administrative controls and personal protective equipment). Two test cases have been introduced to verify the effectiveness of proposed procedure: an ex-post analysis carried out on a real accident occurred during a task execution in a oil storage tank, and an exante assessment for risk prevention during the manufacturing process of a metal tank. Specifically, the

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ex-post analysis shows that essential safety parameters and requirements were omitted during the planning and the design of the intervention in the first confined space. The application of the proposed framework ensures the identification of high-risk confined spaces in industry and the proper

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application of control measures for the elimination or the reduction of the risk. The application of the proposed methodology ensures the recognition of high-risks of confined spaces in industry and the proper identification of control measures for the elimination or the reduction of the risk of confined space work. Employers, employers and safety professional should adopt the proposed framework during planning activities in confined spaces.

Future developments of this study include the validation of the proposed framework through its

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application to multiple case studies from different industries. Many workplaces contain areas that are considered “confined space”, from agriculture to construction industry. Future developments of this study include the test with different work environments, e.g. to investigate the risks of cleaning a grain

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storage silo and to study the risk of inspecting the hull of a ship. Specifically, the framework will be tested in different types of confined spaces, e.g. sewers, tunnels and vessels, to ensure its effectiveness

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and validation in a wide field of applications.

Acknowledgement

This research has been partially funded by the Azienda Unità Sanitaria Locale (AUSL) of Bologna, Italy. The authors are grateful for this support.

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ACCEPTEDforMANUSCRIPT ANSI/ISA (2007). Performance Requirements Instruments Used To Detect OxygenDeficient/Oxygen-Enriched Atmospheres. ANSI/ISA-92.04.01, Part I-2007 (R2013). American National Standards Institute (ANSI), Instrumentation Systems and Automation Society (ISA). ASTM (2012). Standard Practice for Confined Area Entry. ASTM D4276-02(2012). West Conshohocken, PA: American Society for Testing and Materials (ASTM) International.

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Botti, L., Duraccio, V., Gnoni, M. G., & Mora, C. (2015). A framework for preventing and managing risks in confined spaces through IOT technologies. In Safety and Reliability of Complex Engineered Systems - Proceedings of the 25th European Safety and Reliability Conference, ESREL 2015. Botti, L., Ferrari, E., & Mora, C. (2017a). Automated entry technologies for confined space work activities: A survey. Journal of Occupational and Environmental Hygiene, 14(4). https://doi.org/10.1080/15459624.2016.1250003

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Botti, L., Bragatto, P.A., Duraccio, V., Gnoni, MG.G., Mora, C. (2016). Adopting IOT technologies to control risks in confined space: a multi-criteria decision tool. Chemical Engineering Transactions 53, 127-132. Burlet-Vienney, D., Chinniah, Y. & Bahloul, A. & Roberge B. (2015a). Design and application of a 5 step risk assessment tool for confined space entries, Safety Science, 80, pp. 144-155, ISSN 0925-7535.

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ACCEPTED MANUSCRIPT Safe confined space work in the process industry: a structured procedure

Lucia Botti, Vincenzo Duraccio, Maria Grazia Gnoni, Cristina Mora

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Highlights Procedure for analyzing and managing risks in confined spaces.

The procedure includes a stepwise framework to assess and control risks of confined space work.

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The framework collects the concepts and requirements from the fragmented regulations on confined space work.

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Two test cases show the application of the proposed procedure to different confined spaces in industry.