CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 1

Safety Bulletin

U.S. Chemical Safety and Hazard Investigation Board

February 2010

Seven Key Lessons to Prevent Worker 

Deaths During Hot Work In and Around Tanks

Effective Hazard Assessment and Use of Combustible Gas Monitoring 

Will Save Lives

No. 2009-01-SB

Depiction of hot work from the CSB’s 2008 safety video “Death in the Oilfield.” 
	CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 2

Emergency response 

efforts following a June 5, 

2006, accident at the 

Partridge Raleigh Oilfield. 

Courtesy of Smith County 

Sheriff’s Office.

“It is usual to test for the presence of flammable gas or vapor with a combustible gas detector before maintenance, 

especially welding or other hot work, is allowed to start.” (Kletz, Trevor, What Went Wrong, 1999, 4th ed., p.16 )2

What is Combustible Gas Monitoring?

Flammable gas and vapor concentrations are generally determined using a portable combustible gas detector, also called 

an LEL3 meter. Combustible gas detectors are relatively inexpensive and widely available. Training in LEL instrument use is a 

key component to effective gas testing and is a critical aspect of an effective hot work safety program.

INTRODUCTION 

The CSB has identified over 60 fatalities since 1990 due 

to explosions and fires from hot work activities on tanks. 

Hot work is defined as “[w]ork involving burning, welding, 

or a similar operation that is capable of initiating fires or 

explosions.”1 Hot work also includes other activities with 

the potential to create a source of ignition such as cutting, 

brazing, grinding, and soldering. Workers are potentially at 

risk not only in the oil and gas industry, where flammables 

are handled regularly, but also in many other sectors within 

general industry, such as food production, paper, and 

wastewater treatment. 

This bulletin summarizes 11 accidents – nine of which 

the agency has investigated – to highlight seven key lessons 

that were found to be applicable to all or most of the 

incidents, especially the need for effective hazard assessment 

and proper monitoring of potentially flammable air 

concentrations in work areas.

The OSHA hot work standard 29 CFR 1910.252, which 

addresses welding, cutting and brazing, and a voluntary 

consensus standard from the National Fire Protection 

Association (NFPA), define practices that should be implemented during the performance of hot work. 

This bulletin, however, focuses on seven key lessons drawn 

from incidents to emphasize recurring safety issues that 

deserve special attention during hot work operations. For 

a broader discussion of general work practices for hot 

work, the reader should consult these standards, as well as 

other informative sources listed in the references section 

of the bulletin. 

This bulletin comes after a number of recent hot work 

accidents that share all or many of the same safety lessons. 

Seven of the accidents have occurred since July 2008. 

While each accident has unique features, all resulted from 

a flammable vapor coming in contact with an ignition 

source created by welding or cutting that was performed 

in, on, or near tanks that contained flammables. In some 

cases, the presence of a flammable material was completely 

unknown to the workers; in all cases, the workers had no 

knowledge that an explosive amount of flammable vapor 

had accumulated. While much can be learned from these 

hot work accidents, this bulletin highlights seven specific 

lessons that the CSB concludes will have the greatest safety 

impact if implemented in the workplace.
	CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 3

SEVEN KEY LESSONS FROM RECENT HOT WORK ACCIDENTS 

The importance of these lessons is evident upon review 

of the 11 accidents briefly described in this bulletin. While 

each lesson will reduce the likelihood of a catastrophic 

hot work accident, special attention should be paid to 

Key Lessons #2 and #3 – the importance of analyzing the 

hazards and utilizing a combustible gas detector to 

monitor for a potential flammable atmosphere.

These safety lessons are not new; the Environmental 

Protection Agency (EPA) in 1997 issued a Chemical Safety 

Alert warning of recent serious aboveground atmospheric 

storage tank accidents involving flammable vapor explosions, 

a number of which were ignited by hot work. The EPA 

recommended hazard reduction measures that included 

improved hazard assessment and “proper testing of the 

atmosphere for explosivity.”12 

While the OSHA standard prohibits hot work in an 

explosive atmosphere, it does not explicitly require the use 

of a combustible gas detector. However, other good practice 

guidance documents from the National Fire Protection 

Association (NFPA), American Petroleum Institute (API), 

and FM Global stress the need for gas monitoring to prevent 

fires and explosions. For example, NFPA 326 requires the 

use of gas detectors when conducting cleaning, repairs, 

or hot work on or inside tanks and containers that hold 

or have held flammables. (All 11 accidents described in 

this bulletin involved hot work in, on, or near tanks that 

contained flammables.) Gas testing must be conducted 

“before and during any hot work, cutting, welding, or 

heating operations.”13 If the LEL rises to 10%, NFPA 326 

requires that all work shall be stopped and the source of the 

flammable atmosphere located and eliminated or controlled.

For the cases described in this bulletin, an appropriate 

safety management system, including an analysis of the 

hazards and the proper use of a combustible gas detector, 

would likely have alerted workers to the presence of a 

flammable atmosphere before disaster occurred.

The 11 incidents are divided into two categories: 1) those 

cases where no gas monitoring was conducted; and 

2) those where gas testing was improperly conducted.

1. Use Alternatives – Whenever possible, avoid hot work 

and consider alternative methods.4

2. Analyze the Hazards – Prior to the initiation of hot 

work, perform a hazard assessment that identifies the 

scope of the work, potential hazards, and methods of 

hazard control.5

3. Monitor the Atmosphere – Conduct effective gas 

monitoring in the work area using a properly calibrated 

combustible gas detector6 prior to and during hot work 

activities, even in areas where a flammable atmosphere 

is not anticipated. 

4. Test the Area – In work areas where flammable liquids 

and gases are stored or handled, drain and/or purge all 

equipment and piping before hot work is conducted.7

When welding on or in the vicinity of storage tanks and 

other containers, properly test and if necessary continuously monitor all surrounding tanks or adjacent spaces 

(not just the tank or container being worked on) for the 

presence of flammables and eliminate potential sources 

of flammables. 

5. Use Written Permits – Ensure that qualified personnel 

familiar with the specific site hazards review and 

authorize all hot work and issue permits specifically 

identifying the work to be conducted and the 

required precautions.8

6. Train Thoroughly – Train personnel on hot work 

policies/procedures, proper use and calibration 

of combustible gas detectors, safety equipment, and 

job specific hazards and controls in a language 

understood by the workforce.9

7. Supervise Contractors – Provide safety supervision 

for outside contractors conducting hot work.10 Inform 

contractors about site-specific hazards including the 

presence of flammable materials.11

“Avoid hot work of any kind in areas handling, processing or storing flammable 

liquids or gases.”

“Use a portable combustible gas analyzer before and during the work. If any detectible 

readings are obtained, then work cannot begin or continue until the source is found 

and suitably mitigated such that the concentration is maintained below 10% of the 

LFL.” (FM Global, Property Loss Prevention Data Sheet 10-3, 2006, p.4) 

Example of a combustible 

gas detector used to 

test for the presence of 

flammable gas or vapor.
	CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 4

HOT WORK ACCIDENTS WHERE GAS TESTING 

WAS NOT PERFORMED

In seven of the 11 accidents discussed in this bulletin, 

no gas testing was performed prior to or during the 

hot work activities. In these cases, an effective hazard 

evaluation and the proper use of gas monitoring 

equipment likely would have alerted workers to the 

unsafe work conditions.

A.V. Thomas Produce

Atwater, California, March 31, 2009

2 Workers Severely Burned

Two employees at A.V. Thomas Produce were using an 

oxygen-acetylene torch to loosen a fitting on an old fuel 

tank, which the company hoped to refurbish for field 

storage of diesel fuel. The workers, however, were 

unaware that the tank contained residual hydrocarbon 

liquid and vapor from an unknown prior use. The tank 

was not cleaned or purged before work began. Shortly 

after applying heat to the tank, an explosion occurred, 

blowing the end of the vessel off. Both employees were 

airlifted to a regional burn center, where they were treated 

for burns covering 30 to 50% of their bodies.

The facility had no formal hot work program, and no 

permit was issued for the hot work being performed. 

No combustible gas testing was performed prior to 

commencement of the hot work; the company did not 

have a policy that required it. In addition, many workers 

were mono-lingual Spanish speakers and had not been 

trained on safe hot work procedures or on the proper use 

of gas detectors in their native language.

Exterior and interior views of the fuel tank involved in the hot work accident at A.V. Thomas Produce. 

Applicable Key Lessons

Analyze the Hazards, Monitor the Atmosphere, 

Test the Area, Use Written Permits, Train Thoroughly
	CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 5

EMC Used Oil Corporation

Miami, Florida, December 2, 2008

1 Worker Killed, 1 Injured

An explosion killed a contract welder who was 

repairing a two-compartment oil tanker and injured 

another worker at the EMC Used Oil facility. The 

welder was in the process of welding transfer piping 

onto the tanker when residual hydrocarbon vapor from 

the 2,500-gallon rear compartment ignited, causing a 

powerful explosion. 

Damage to an oil tanker 

sustained from the 

December 2, 2008, 

explosion at EMC Used 

Oil Corporation.

The surviving worker stated that the contractors did not 

perform combustible gas monitoring and relied upon the 

host company to assure that tanks were safe for hot work. 

However, EMC indicated that it relied on contractors 

to monitor for gas; although the company owned a multiple gas detector, it was used only for confined space entry. 

EMC did not have a formal hot work permitting or 

authorization system. 

Applicable Key Lessons

Use Alternatives, Analyze the Hazards, Monitor the 

Atmosphere, Test the Area, Use Written Permits, 

Supervise Contractors
	CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 6

MAR Oil

La Rue, Ohio, October 19, 2008

2 Workers Killed

An explosion killed two contract workers while they were 

welding above a series of three interconnected crude oil 

storage tanks at a MAR Oil site. The explosion occurred 

when the workers attempted to weld a bracket on top of 

one of the tanks, near an atmospheric vent. Because the 

tanks were interconnected, oil flowing into an adjacent 

tank likely displaced flammable vapor into the tank being 

welded. The vapor escaped through the vent and was 

ignited by welding sparks.

The CSB investigators found that combustible gas monitoring was not performed prior to or during the welding. There 

is conflicting evidence as to whether or not the welding job 

was authorized by the host company. MAR Oil lacked a 

formal hot work program that required the hot work be 

identified in a written permit and be authorized by a person 

responsible for hot work management. The company had 

no formal program to select or oversee contractors, and the 

two contractors lacked documented training on safe hot 

work practices. 

Oil storage tanks involved in fire and explosion at MAR Oil.

Applicable Key Lessons

Use Alternatives, Analyze the Hazards, Monitor 

the Atmosphere, Test the Area, Use Written Permits, 

Train Thoroughly, Supervise Contractors

Philip Services Corporation14

Kapolei, Hawaii, October 7, 2008

1 Worker Killed, 3 Injured

A contract welder was killed while welding on a 

catwalk located over a 9,300-gallon waste oil storage 

tank at the Philip Services Corporation (PSC). Following 

an investigation, the Honolulu Fire Department (HFD) 

concluded that, during the welding, sparks dropped in 

and around the vent area of the tank. The contents of the 

tank ignited, resulting in an explosion and fire. The force 

of the explosion hurled the contract welder about 120 

feet, fatally injuring him. Three others were injured, and 

the tank was thrown about 30 feet.

According to the HFD investigation, a PSC official 

asserted that the contractors were not authorized to 

weld within the dike area surrounding the tank, a hot 

work permit had not been issued for the welding, 

and combustible gas monitoring was not conducted. 

Conversely, the contracting company’s personnel asserted 

that they believed that the work was authorized and that 

PSC had conducted combustible gas monitoring prior to 

the welding activity.

View of Philip Services Corporation following a October 7, 2008, 

waste oil storage tank explosion.

Applicable Key Lessons

Use Alternatives, Analyze the Hazards, Monitor 

the Atmosphere, Test the Area, Use Written Permits, 

Supervise Contractors 
	CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 7

Packaging Corporation of America 

Tomahawk, Wisconsin, July 29, 2008

3 Workers Killed, 1 Injured 

Three workers were killed in an explosion at the 

Packaging Corporation of America (PCA) fiberboard 

manufacturing facility while they were welding on 

a temporary metal clamp to stabilize a damaged flange 

connection. The flange was located on top of an 

80-foot tall storage tank that contained recycled water 

and fiber waste.

Facility personnel were unaware of the potential presence 

of flammable gas from the decomposition of the organic 

material in the tank, and combustible gas monitoring 

was not typically required or performed prior to starting 

work. At the time of the accident, three workers were 

on a catwalk above the tank; one began welding the 

flange into place when sparks from the welding ignited 

flammable vapors inside the tank. The resulting explosion 

ripped open the tank lid, knocking two of the workers 

to the ground 80 feet below. All three workers died 

of traumatic injuries. A fourth worker, who had been 

observing the work from a distance, survived with 

minor injuries.

The CSB analysis of the tank contents determined that 

anaerobic bacteria had multiplied inside the tank and 

water recycle system over time, feeding on organic waste 

material. The bacteria likely produced hydrogen, a 

highly flammable gas, which ignited during the welding 

work. The CSB found that at the time of the incident, 

PCA supervisors and workers were unaware of the risks 

of flammable gas production from anaerobic bacteria 

growth. PCA did not perform a hazard analysis or 

recognize fiber waste tanks as potentially hazardous. 

Combustible gas monitoring was not required for 

the work. 

Applicable Key Lessons

Analyze the Hazards, Monitor the Atmosphere, 

Test the Area

Views of the storage tank involved in the 2008 explosion at Packaging Corporation of America.
	CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 8

Bethune Point Wastewater Plant

Daytona Beach, Florida, January 11, 2006

2 Workers Killed, 1 Critically Injured

Two workers were killed and another critically injured 

in an explosion involving a methanol storage tank at a 

municipal wastewater treatment facility in Daytona Beach, 

Florida. The explosion occurred while the three workers 

were cutting a metal roof located directly above the tank 

vent. Sparks showered from the cutting torch and ignited 

methanol vapor escaping from the vent, creating a fireball 

on top of the tank. A corroded and ineffective flame 

arrester15 on the vent allowed the fire to propagate through 

the device, igniting methanol vapors and air inside the 

tank, resulting in an explosion.

Daytona Beach public employees were not covered by 

OSHA standards, which is typical for local and state 

governments in a number of jurisdictions. The city had 

no formal permitting system for hot work or non-routine 

maintenance activities, and workers had not received any 

training on methanol hazards in the previous 10 years. 

Combustible gas monitoring was not performed or required.

Partridge-Raleigh Oilfield

Raleigh, Mississippi, June 5, 2006

3 Killed, 1 Seriously Injured

On June 5, 2006, contract workers were installing 

a new pipe between two oil tanks at a rural oilfield 

when sparks from a welding torch ignited flammable 

hydrocarbon vapor venting from one of the tanks. That 

tank and another nearby tank exploded, killing three 

workers who were standing above the tanks and seriously 

injuring a fourth. As in the MAR Oil accident, all of the 

tanks were interconnected by piping and one of the tanks 

contained crude oil, the source of the vapor that fueled 

the explosions.

The workers had not performed combustible gas 

monitoring prior to or during the hot work, instead 

relying on the unsafe and unreliable practice of 

using a lit torch to check one of the tanks for flammable 

vapor. Workers did not empty or isolate the tank that 

contained crude oil prior to initiating hot work activities.

Neither the contract company nor Partridge-Raleigh 

required written hot work permits. The contractor 

company did not provide hot work safety training to 

employees. Furthermore, Partridge-Raleigh did not 

have safety requirements for its oilfield contractors.

Applicable Key Lessons

Use Alternatives, Analyze the Hazards, Monitor the 

Atmosphere, Test the Area, Use Written Permits, 

Train Thoroughly

The CSB issued a report and safety video on the Bethune 

Point Wastewater Plant accident in March 2007. Both the 

report and video are available from www.CSB.gov. 

Tanks involved in the 2006 accident that killed three workers at the 

Partridge-Raleigh Oilfield.

Applicable Key Lessons

Use Alternatives, Analyze the Hazards, Monitor 

the Atmosphere, Test the Area, Use Written Permits, 

Train Thoroughly, Supervise Contractors 

The CSB issued a report and safety video on the 

Partridge-Raleigh accident in 2007. Both the report and 

video are available from www.CSB.gov. 

Depiction of hot work from the CSB’s 2007 “Public Worker Safety” 

video illustrating the accident at Bethune Point.
	CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 9

HOT WORK ACCIDENTS WHERE 

IMPROPER GAS TESTING WAS PERFORMED

gas monitoring are performed improperly. The ineffective 

hazard assessment and monitoring practices used in these 

cases failed to identify the presence of a flammable atmosphere in the area where hot work was being conducted.

The accidents reviewed thus far demonstrate the need to 

monitor the atmosphere for dangerous levels of flammable 

vapor. The next four accidents demonstrate how hot work 

can have catastrophic results when hazard assessments and 

TEPPCO Partners, LP

Garner, Arkansas, May 12, 2009

3 Workers Killed

Three contractors were using a cutting torch on top of the 

internal floating roof of a 67,000-barrel capacity gasoline 

storage tank at the TEPPCO Partners McRae Terminal 

when an internal explosion blew both the top of the floating 

roof and the secondary dome-shaped lid off the tank. All 

three were killed. The contractors were preparing to install 

a gauge pole. The gauge floats within the pole and measures 

the quantity of product within the tank. Part of the installation process involved cutting an opening into the floating 

roof for the pole to be inserted. The torch-cutting activity 

most likely ignited flammable vapor within the tank. 

Prior to commencing work, the contractors had been issued 

both a confined space permit to enter the tank and a hot 

work permit to torch-cut the roof. The hot work permit 

indicated that gas testing occurred at 7:00 am, the start of 

the work shift. However, no documentation exists indicating 

that gas testing was conducted after the workers returned 

from lunch or when they started the hot work activities just 

prior to the explosion at approximately 2:30 pm. Work 

atmospheres can change rapidly; gas monitoring needs to 

be conducted immediately prior to and during hot work 

activities to ensure that workers are constantly aware of 

the potential development of an explosive atmosphere.

The gasoline storage tank at the 

TEPPCO McRae Terminal following the 2009 hot work accident 

that killed three workers.

To effectively use a combustible gas detector, consider the characteristics of the gas 

(lighter or heavier than air) as well as the appropriate locations and frequency of test. 

Training of personnel and proper maintenance, adjustment and calibration of the device are 

also crucial for effective gas detector use. (API Recommended Practice 2009, 2002, p.12) 

Applicable Key Lessons

Analyze the Hazards, Monitor the Atmosphere, 

Test the Area, Supervise Contractors
	CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 10

ConAgra Foods

Boardman, Oregon, February 16, 2009

1 Worker Killed

A welding contractor was killed while repairing a 1 1⁄4 

by 1⁄2 inch crack on the bottom of a water clarifier tank at 

a ConAgra Foods facility. The 23-foot-tall tank was used 

to separate dirt and debris from wastewater in a potatowashing process area. The tank was open at the top and had 

a metal skirt around its cone-shaped base. While the welder 

was working inside the tank, an explosion occurred; the 

internal tank structures collapsed, resulting in his death. 

The CSB determined that approximately 14 inches of 

debris-laden water had leaked through the crack in the 

tank and accumulated in the hidden space under the tank 

skirting. Examination of a sample of the liquid indicated 

that bacterial decomposition of the organic matter likely 

produced flammable gas, which was then ignited by the 

welding activity. 

In this case, ConAgra personnel had tested for combustible 

gas inside the tank prior to the hot work, but only from the 

entrance of the tank and no flammable gas was detected. 

Monitoring for combustible gases was not conducted in 

the immediate area of the crack just prior to the initiation 

of the welding or in the adjacent space where flammable 

gas was present. Personnel were inadequately trained on 

the use of the specific combustible gas detector that was 

used and no hot work permit had been issued prior to 

commencing the welding.

Applicable Key Lessons

Analyze the Hazards, Monitor the Atmosphere, 

Test the Area, Use Written Permits, Train Thoroughly

Potato-washing tank involved in the February 2009 accident at ConAgra Foods.
	CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 11

Motiva Enterprises Refinery

Delaware City, Delaware, July 17, 2001

1 Killed, 8 Injured 

A massive explosion destroyed a large storage tank 

containing a mixture of sulfuric acid and flammable 

hydrocarbons at the Motiva Enterprises Delaware City 

Refinery. One contract worker was killed, eight others 

were injured, and sulfuric acid from collapsed and 

damage tanks polluted the Delaware River. The explosion 

occurred during welding operations to repair a catwalk 

above the sulfuric acid tank, when flammable hydrocarbon 

vapor was ignited by welding sparks. This resulted in a 

powerful explosion inside the tank, which had holes in its 

roof and shell and a deficient inerting system.

On the day of the accident, combustible gas testing was 

performed only at the start of the hot work, but monitoring 

was not conducted for the duration of the hot work 

activities. Throughout the five hours between the last gas 

test and the explosion, the ambient temperature warmed 

by 14 degrees. This warming increased the evaporation of 

hydrocarbons inside the tank, and the resulting flammable 

vapor leaked out the tank’s holes into the work area.

Motiva had a hot work program that included written 

permits, but the program was inadequate. Hot work was 

allowed near tanks that contained flammables including 

those that had known holes due to corrosion. Continuous 

atmospheric monitoring and the control of welding sparks 

were not required.

The CSB issued its final report on the causes of the 

Motiva Refinery accident in August 2002. It is available 

from www.CSB.gov.

Pennzoil Refinery

Rouseville, Pennsylvania, October 16, 1995 

5 Killed 

While this case was not investigated by the CSB 

because the agency was not yet funded and operational, 

the catastrophic nature of this hot work accident and the 

lessons learned from it support the case’s inclusion in this 

bulletin. An explosion and fire resulted during hot work 

activities, killing five employees; the ensuing fire forced 

the evacuation of the refinery and nearby residents. 

The EPA investigated the incident and found that a welding 

operation was in progress on a service stairway located 

between two liquid storage tanks that contained mixtures 

of waste hydrocarbons and water. The explosion was 

attributed to the ignition of flammable vapor from one of 

the tanks. The EPA report found that “the tanks containing 

combustible or flammable vapors were not thoroughly 

isolated from the hot work site .... Although combustible 

gas testing prior to the start of hot work early in the 

morning indicated vapors were not present, gradual 

warming could make the presence of combustible vapors 

more likely.”16 According to the report, gas monitoring 

was apparently not repeated during the midmorning hours 

when the explosion occurred. The EPA recommends that 

facilities evaluate the need for continuous combustible gas 

monitoring during hot work activities.

Applicable Key Lessons

Use Alternatives, Analyze the Hazards, Monitor 

the Atmosphere, Test the Area, Supervise Contractors 

Applicable Key Lessons

Analyze the Hazards, Monitor the Atmosphere, 

Test the Area

A view of the flammable storage tank involved in the accident at the 

Motiva Refinery.
	CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 12

CONCLUSION

Although the hazards of hot work are well established 

and both regulatory and good-practice guidance exist, 

frequent deaths and serious injuries continue to occur in 

hot work-related fires and explosions. The CSB has found 

that hot work is one of the most common causes of worker 

deaths among accidents it investigates. Following the seven 

key lessons in this bulletin – along with other good safety 

practices – can prevent deaths and injuries from hot work.

In particular, host companies, contractors, permit 

writers, welders, and other maintenance workers should 

effectively analyze the hazards and conduct combustible 

gas monitoring before and during hot work to provide 

advance warning of flammable atmospheres. Training 

on the proper use of such devices is imperative for future 

hot work accident prevention.

REFERENCES AND ADDITIONAL INFORMATION

American Petroleum Institute (API). Safe Welding, 

Cutting and Hot Work Practices in the Petroleum and 

Petrochemical Industries, Recommended Practice (RP) 

2009, Washington, DC, 2002. 

Association of Energy Service Companies (AESC). 

Hot Work, Health, Safety, and Environmental Committee 

Technical Advisory Group publication, retrieved on-line at 

http://www.aesc.net/pdf/Hotwork.pdf on August 25, 2009.

Environmental Protection Agency (EPA). Catastrophic 

Failure of Storage Tanks Caused by Vapor Explosion, 

Chemical Safety Alert, EPA 550-G-97-002b, May 1997.

EPA. Chemical Accident Investigation Report, Pennzoil 

Company Refinery, Rouseville, Pennsylvania, March 1998.

FM Global. Property Loss Prevention Data Sheet 10-3: 

Hot Work Management, FM Global, Norwood, MA, 2006. 

Kletz, Trevor. What Went Wrong? Case Histories of 

Process Plant Disasters, 4th Ed., Woburn, MA, 1999.

Levine, Steven P. & Thornton James, R. LEL monitoring 

during hazard surveys for issuance of hot work permits: 

the need for definitive requirements, Professional Safety, 

February 2004.

National Fire Protection Association (NFPA). Standard 

for Fire Prevention During Welding, Cutting and Other 

Hot Work, NFPA 51B, 2009.

NFPA. Standard for the Safeguarding of Tanks and 

Containers for Entry, Cleaning, or Repair, NFPA 326, 

2005.

Occupational Safety and Health Administration (OSHA). 

General Requirements for Welding, Cutting, and Brazing, 

29 CFR 1910.252.

Rescue efforts following the February 16, 2009, hot work accident at ConAgra Foods in Boardman, Oregon.
	CSB • Seven Key Lessons to Prevent Worker Deaths During Hot Work In and Around Tanks 13

The U.S. Chemical Safety and Hazard Investigation Board (CSB) is an independent federal agency charged with investigating industrial 

chemical accidents. The agency’s board members are appointed by the president and confirmed by the Senate. CSB investigations 

look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in regulations, 

industry standards, and safety management systems. 

The Board does not issue citations or fines but does make safety recommendations to companies, industry organizations, labor groups, 

and regulatory agencies such as OSHA and EPA. Please visit our website, www.csb.gov. 

No part of the CSB’s conclusions, findings, or recommendations may be admitted as evidence or used in any action or suit for damages; 

see 42 U.S.C. § 7412(r)(6)(G).

 1 NFPA 51B, 2009, p. 51B-5.

 2 In What Went Wrong, Kletz describes a number of accidents that 

demonstrate the serious consequences resulting from a failure to 

conduct combustible gas testing.

 3 The LEL, or Lower Explosive Limit, is the concentration of a 

combustible material in air capable of propagating a flame in the 

presence of an ignition source. It is also known as the Lower 

Flammability Limit (LFL). 

4 FM Global Data Sheet 10-3, 2006, p. 2-3. OSHA 1910.252 

requires moving the hot work or fire hazard to a safe location. This 

guidance applies to hot work conducted outside of a designated 

area approved for hot work such as a maintenance shop. If the 

hot work or hazard cannot be relocated, OSHA requires guards to 

confine the sources of ignition and the protection of fire hazards. 

For additional guidance, see NFPA 51B, 2009, p. 51B-6. 

 5 For more information on conducting hot work hazard analyses, see 

OSHA’s 1910.252(a)(2)(xiv)(A) and (B); NFPA 51B, 2009, p. 51B-6; 

Levine, S. P. & Thornton J. R., 2004, p. 31-39, and API RP2009, 

2002, p. 5.

 6 For more information about the recommended use of a 

combustible gas detector, see FM Global, 2006, p. 4; Levine, S. P. 

& Thornton J. R., 2004, p. 31-39; and the Association of Energy 

Service Companies (AESC) safety guidance “Hot Work.” Additionally, 

API RP2009, 2002, p. 12 states “(a) competent person using 

an appropriate combustible-gas meter should perform tests to 

determine flammable vapor concentrations before hot work is 

started.” While the API RP2009 applies expressly to the petroleum 

and petrochemical industries, it provides persuasive guidance 

to general industry on safe hot work management practices 

especially where flammables may be present.

 7 OSHA in 1910.252(a)(3)(i) prohibits hot work on drums, tanks, 

and other containers until they have been thoroughly cleaned to 

remove flammable materials or other substances that when 

subject to heat may produce flammable or toxic vapors. For more 

information on proper cleaning and inerting of equipment, see FM 

Global Data Sheet, 10-3, 2006, p. 4. 

 8 For more information, see OSHA 29 CFR 1910.252(a)(2)(iv). 

This regulation prefers but does not require a written permit for hot 

work; however, good practice guidance NFPA 51B, 2009, p. 51B6 and API RP2009, 2002, p. 13 both recommend written work 

permits for hot work. However, for facilities covered under OSHA’s 

Process Safety Management Standard, 1910.119 a permit is 

required for hot work conducted on or near a process covered by 

the standard (1910.119(k)(1)).

 9 OSHA 29 CFR 1910.252(a)(2)(xiii)(C); NFPA 51B, 2009, p. 51B-5; 

and FM Global Data Sheet 10-3, 2006, p. 4 require training on 

hot work safe practices.

10 FM Global Data Sheet 10-3, 2006, p. 8 states: “FM Global loss 

history shows the risk of fire can increase over 100% when outside 

contractors are involved in hot work without facility supervision.”

11 OSHA 29 CFR 1910.252(a)(2)(xiii)(D) requires and NFPA 51B, 

recommends that management inform all contractors about the 

presence of all flammable materials, hazardous processes, and 

potentially hazardous conditions.

12 EPA, Catastrophic Failure of Storage Tanks Caused by Vapor 

Explosion, May 1997, p. 4.

13 NFPA 326, 2005, p. 326-8. The text of NFPA’s general hot work 

standard 51B does not require combustible gas testing but the 

Explanatory Material of 51B (A.5.3) references NFPA 326. 

14 The CSB did not deploy investigators to the Philip Services 

Corporation site in Hawaii but reviewed case evidence, including a 

report provided by the Honolulu Fire Department, Incident Report 

2008-0038474-000.

15 Flame arresters are safety devices that, when properly maintained, 

stop a flame while allowing gases and vapors to flow freely.

16 EPA, 1998, Chemical Accident Investigation Report, Pennzoil 

Company Refinery, p. iii.

ENDNOTES

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