U.S. CHEMICAL SAFETY AND HAZARD INVESTIGATION BOARD

INVESTIGATION REPORT 

REPORT NO. 2003-08-I-RI 

AUGUST 2004

VENT COLLECTION SYSTEM EXPLOSION

(1 Critically Injured, 18 Medical Evaluations, Community Evacuation) 

TECHNIC INC. 

CRANSTON, RHODE ISLAND

FEBRUARY 7, 2003 KEY ISSUES: 

• INCOMPATIBLE CHEMICAL MIXING 

• PROCESS SAFETY REVIEW

• MANAGEMENT OF CHANGE

• PREVENTIVE MAINTENANCE

• EMERGENCY PLANNING AND RESPONSE
Technic Inc. 08-20-04 

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Contents 

EXECUTIVE SUMMARY ..........................................................................................................................8

1.0 INTRODUCTION .........................................................................................................................10

1.1 Background....................................................................................................................................10

1.2 Investigative Process......................................................................................................................10

1.3 Vent Collection System Process Description.................................................................................11

1.4 Technic Inc. ...................................................................................................................................13

2.0 INCIDENT DESCRIPTION..........................................................................................................15

2.1 Employee Injuries..........................................................................................................................15

2.2 Facility Damage.............................................................................................................................16

3.0 INCIDENT RESPONSE................................................................................................................17

3.1 Employee Evacuation ....................................................................................................................17

3.2 Firefighting ....................................................................................................................................17

3.3 Decontamination of Exposed Employees ......................................................................................18

3.4 Community Evacuation .................................................................................................................18

4.0 VENT COLLECTION SYSTEM..................................................................................................19

4.1 Design, Permitting, and Installation...............................................................................................19

4.2 System Modifications ....................................................................................................................20

4.3 Loss Prevention Carrier Review ....................................................................................................21

5.0 INCIDENT ANALYSIS................................................................................................................24

5.1 Explosion and Fire Analysis ..........................................................................................................24

5.2 Chemical Reaction Analysis..........................................................................................................29

5.2.1 Shock-Sensitive Explosive Silver Compounds.................................................................31
Technic Inc. 08-20-04 

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5.2.2 Silver Nitrate Reacting With Another Compound............................................................32

6.0 ANALYSIS OF SAFETY MANAGEMENT SYSTEMS.............................................................34

6.1 Process Safety Review for Projects ...............................................................................................34

6.2 Management of Change .................................................................................................................35

6.3 Process and Equipment Integrity ...................................................................................................37

6.4 Emergency Planning and Response...............................................................................................37

6.4.1 Facility Emergency Planning and Response.....................................................................38

6.4.2 Community Emergency Planning and Response..............................................................40

7.0 REGULATORY AND INDUSTRY STANDARDS ANALYSIS ................................................41

7.1 Environmental, Safety, and Health Regulations ............................................................................41

7.1.1 OSHA Process Safety Management .................................................................................41

7.1.2 EPA Risk Management Program......................................................................................41

7.1.3 OSHA Ventilation Standards............................................................................................42

7.1.4 Clean Air Act....................................................................................................................42

7.1.5 Emergency Planning and Community Right-to-Know Act ..............................................43

7.2 Mechanical Code ...........................................................................................................................43

7.3 Consensus Standards......................................................................................................................44

7.4 Loss Prevention Guidance .............................................................................................................46

8.0 ROOT AND CONTRIBUTING CAUSES....................................................................................48

8.1 Root Causes ...................................................................................................................................48

8.2 Contributing Causes.......................................................................................................................49

9.0 RECOMMENDATIONS...............................................................................................................50

10.0 REFERENCES ..............................................................................................................................52

APPENDIX A: TECHNIC PRODUCTION AND PROCESSES .............................................................55
Technic Inc. 08-20-04 

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APPENDIX B: CALORIMETRIC TESTING ..........................................................................................60

APPENDIX C: CAUSAL FACTORS DIAGRAM...................................................................................63
Technic Inc. 08-20-04 

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Figures 

1 Vent Collection System and Connected Processes........................................................................12

2 Aerial Photo of Technic Facility....................................................................................................14

3 Vent Collection System as of February 7, 2003 ............................................................................22

4 Sharp Fracture of 4-Inch Exhaust Duct Above Tank 8..................................................................24

5 Large Fracture of 10-Inch Branch Duct Above Mezzanine 2 Production Area.............................25

6 Depiction of Explosion and Fire Damage, February 7, 2003 ........................................................26

7 Remains of Acid Hood on Mezzanine 1 ........................................................................................27

8 Collapsed 36-Inch-Diameter Main Header at Scrubber Along East Wall .....................................27

9 Blistered Char Inside 36-Inch-Diameter Main Header Adjacent to Mezzanine 1 .........................29

10 Solid Deposits in Main Header Duct .............................................................................................30

11 Layers of Protection in a Modern Chemical Plant.........................................................................38

A-1 Kestner Unit Exhaust Ventilation ..................................................................................................56

A-2 Silver Nitrate Reactor on Mezzanine 1 With Open Tank Door .....................................................56

Tables 

1 VCS Explosion and Fire Damage Detail .......................................................................................28
Technic Inc. 08-20-04 

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Acronyms and Abbreviations 

ACGIH American Conference of Governmental Industrial Hygienists 

AgCN Silver cyanide 

AgNO3 Silver nitrate 

AIChE American Institute of Chemical Engineers 

AIHA American Industrial Hygiene Association 

ANSI American National Standards Institute 

ASTM American Society for Testing and Materials 

BOCA Building Officials and Code Administrators, Inc. 

CAA Clean Air Act 

CCPS Center for Chemical Process Safety 

CFD Cranston Fire Department 

CFR Code of Federal Regulations 

CSB U.S. Chemical Safety and Hazard Investigation Board 

CWRT Center for Waste Reduction Technology 

DOT U.S. Department of Transportation 

DSC Differential scanning calorimetry 

EPA U.S. Environmental Protection Agency 

EPCRA Emergency Planning and Community Right-to-Know Act 

oF Degrees Fahrenheit 

FEMA Federal Emergency Management Agency 

FM Factory Mutual Insurance Company 

GDC General duty clause (OSHA) 

ICC International Code Council 

IDLH Immediately Dangerous to Life and Health 
Technic Inc. 08-20-04 

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IPCS International Program on Chemical Safety 

ISO International Standards Organization 

LEPC Local emergency planning committee 

MOC Management of change 

NFPA National Fire Protection Association 

ORNL Oak Ridge National Laboratory 

OSHA Occupational Safety and Health Administration 

PSM Process Safety Management (OSHA) 

RI–DEM Rhode Island Department of Environmental Management 

RMP Risk Management Program (EPA) 

SARA Superfund Amendments and Reauthorization Act 

SCBA Self-contained breathing apparatus 

USFA U.S. Fire Administration 

VCS Vent collection system 
Technic Inc. 08-20-04 

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Executive Summary 

On Friday, February 7, 2003, at approximately 9:30 am, an explosion ignited a fire inside a vent 

collection system (VCS) at Technic Inc., a plating chemicals manufacturing and research facility located 

in Cranston, Rhode Island. One employee was critically injured. Eighteen other employees were 

transported to Rhode Island Hospital for medical evaluation. The vent collection system was severely 

damaged, and plant operations were interrupted for several weeks. 

In addition to evacuating plant employees, the Cranston Fire Department (CFD) ordered an evacuation of 

residents and businesses within 0.5 mile of the facility because of concern that cyanide salts and acids 

stored in the plant might combine to create toxic hydrogen cyanide gas. 

According to witness testimony, the incident likely began when an employee—suspecting the plastic 

ventilation duct to be clogged—tapped on it with a small hammer. The resulting explosion severely 

injured his eyes and face. The U.S. Chemical Safety and Hazard Investigation Board (CSB) determined 

that the hammer blow likely initiated an explosive reaction of chemicals inside the duct. 

The CSB investigation determined the following root causes: 

• Technic did not conduct a process safety review to identify and evaluate the hazards associated 

with installing a vent collection system to handle the exhaust from multiple processes. Such a 

review would have likely included a process hazard analysis to identify and evaluate reactive 

chemical hazards. Competent reviewers would have evaluated and verified the design prior to 

and after installation. 

• Technic did not identify and evaluate the hazards created by changes to facility processes and 

equipment (i.e., management of change). Significant changes made to the vent collection system 

were not envisioned in the original design and significantly deteriorated its performance. Such 
Technic Inc. 08-20-04 

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modifications should have been accompanied by a design and engineering review, a process 

hazard analysis, and before-and-after performance testing to ensure that the system was 

operating as intended. 

In addition, the following contributed to the incident and its consequences: 

• Neither Technic nor CFD adequately planned for this type of emergency. 

• Technic did not have process and equipment integrity procedures or training to inspect or 

maintain the vent collection system. 

CSB makes recommendations to Technic Inc., the National Fire Protection Association, the American 

Industrial Hygiene Association, and the American Conference of Governmental Industrial Hygienists. 
Technic Inc. 08-20-04 

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1.0 Introduction 

1.1 Background 

A February 7, 2003, explosion and fire inside a vent collection system (VCS) at Technic Inc., in 

Cranston, Rhode Island, critically injured one employee, who suffered permanent eye damage and 

chemical burns to his face and upper body. Eighteen other employees were sent to the hospital for 

medical evaluations, and the fire department evacuated the surrounding community. Facility operations 

were interrupted for several weeks. 

The explosion and fire were caused by a violent chemical reaction inside the vent collection system, 

which was likely initiated when the employee tapped on a duct with a small hammer. The building where 

the incident occurred housed several chemical processes that were connected to the ventilation system. 

1.2 Investigative Process 

The U.S. Chemical Safety and Hazard Investigation Board (CSB) arrived at the facility on the evening of 

February 7. CSB investigators examined physical evidence, conducted interviews, and reviewed relevant 

company documents. Samples of residue chemicals from interior surfaces of the vent collection system 

and associated equipment were collected and analyzed. CSB coordinated its investigation with the 

Occupational Safety and Health Administration (OSHA), U.S. Environmental Protection Agency (EPA), 

and Rhode Island State Fire Marshal. 

The Rhode Island General Assembly passed a house resolution on February 26, 2003, requesting that 

CSB prepare a report of its findings regarding the Technic plant explosion. The report would contain the 

Board’s recommendations and proposed policy changes to avoid further mishaps. 
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1.3 Vent Collection System Process Description 

The vent collection system was installed in conjunction with a 1990 plant expansion. The system 

consisted of interconnected polyvinyl chloride duct segments, gradually decreasing in diameter, 

suspended approximately 20 feet above the floor. The purpose of the collection system was to transport 

vapors, gases, and mists emitted from various processes to a scrubber, in compliance with EPA air 

emission standards (Section 4.0). 

The following processes connected to the vent collection system may have contributed to the incident 

(Figure 1): 

• Five silver nitrate solution batch reactors located on mezzanine 1. 

• The Kestner unit (a vessel used to manufacture silver nitrate solutions). 

• Four potassium silver cyanide solution batch reactors located on mezzanine 2. 

• More than 20 plating solution-mixing tanks/reactors located in the kettle room. 

• Two lump removal and packaging stations for silver cyanide and potassium silver cyanide 

powders located in the weigh room. 

• Eleven open surface tanks for gold/silver solutions in the metals reclaim areas. 

With the addition of vent ducts from over 20 process vessels from 1992 to 2003, the demand on the vent 

collection system increased significantly from the time of the plant expansion in 1990. These additions 

were designed and installed without engineering analysis. See Appendix A for detailed descriptions of 

the chemical processes and emissions. 
Technic Inc. 08-20-04 

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Kettle room

Kestner unit

Weigh

room

Technic Inc.

88 Spectacle Street

Cranston, RI

Metals reclaim

areas

Mezzanine 2

Mezzanine 1

Scrubber

Tank 8

(Drawing not to scale or detail.)

VCS ducts & direction of airflow

1990 expansion project

Legend:

Figure 1. Vent collection system and connected processes. 
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1.4 Technic Inc. 

Technic is a privately owned plating chemical and equipment manufacturing company founded in the 

1940s. It is one of the largest volume producers of plating chemicals in the United States. Technic 

products are used for plating precious and nonprecious metals in the electronics and jewelry industries. 

In addition to the Cranston facility, Technic has four other U.S. facilities—located in Anaheim, 

California; Plainview, New York; Clearwater, Florida; and Pawtucket, Rhode Island. The Anaheim and 

Plainview facilities conduct plating research and development, while the Pawtucket and Clearwater 

facilities make specialty equipment for the plating industry. Technic also has facilities in Europe and 

Asia, and employs over 500 people worldwide. 

The Cranston facility employs 150 people, including several chemists. It supplies chemicals to over 

1,000 customers in the United States and abroad. It is located in a mixed residential/industrial 

neighborhood alongside Rhode Island Route 10 (Figure 2). The facility includes two buildings, one of 

which houses the corporate offices and main research laboratories (1 Spectacle Street); the other houses 

the plating chemical manufacturing processes and related laboratories (88 Spectacle Street). The 

manufacturing building was expanded in 1990 to accommodate new production operations. The 

surrounding area included dwellings, businesses, and a recreational center 2 miles from the Technic 

facility. 
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Figure 2. Aerial photo of Technic facility. 

N

Spectacle 

Pond Route 10 

1 Spectacle 

Street 

88 Spectacle 

Street

1990

addition

Guard 

station 
Technic Inc. 08-20-04 

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2.0 Incident Description 

Manufacturing operations at Technic were significantly reduced on the day of the explosion. The 

production of silver cyanide salts had been temporarily suspended due to an employee absence. As a 

result, management had instructed employees to clean up their work areas. 

The employee who was severely injured told CSB investigators that he was cleaning on mezzanine 2 

when he heard a whistling sound coming from the exhaust duct connected to tank 8. He said it sounded 

as if the duct was blocked. After tapping on the duct with a small hammer, he thought he heard some 

loosened material fall into the tank. However, because the duct still sounded blocked, he tapped on it 

again. An instant later—at approximately 9:30 am—the duct exploded, knocking him to the floor. 

Subsequent to the explosion, a fire involving accumulated combustible materials broke out inside the 

main vent header duct. The fire propagated through the main header duct to the branch ducts on 

mezzanine 1 and eventually consumed a plastic acid hood. According to the CFD report, the fire was 

knocked down by 11:34 am, and fire department personnel left the scene at 1:00 pm. 

2.1 Employee Injuries 

Five employees were working in the production area at the time of the explosion, but only the person who 

tapped the pipe was injured. Chemicals from inside the duct struck his face and upper body. After trying 

to flush his face and eyes at two inoperable eyewashes, he made his way to a sink-mounted eyewash in 

the adjacent building, where he was able to splash water onto his face until emergency responders arrived. 

He told CSB investigators that he was wearing wrap-around safety glasses at the time of the explosion 

and that he removed them sometime shortly afterward. 

Emergency medical technicians from the Cranston Fire Department (CFD) arrived within 10 minutes of 

the explosion and began treating the victim. They cut off his shirt, washed his face and upper body with 
Technic Inc. 08-20-04 

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water, and used a saline-soaked cloth to remove chemicals and debris from his eyes, nostrils, and mouth. 

They did not flush his eyes with water because they were unable to determine from the employee, or other 

Technic personnel, exactly what chemicals he had been exposed to. Approximately 30 minutes after the 

first explosion, they decontaminated1

 the victim and placed him in an ambulance for transport to Rhode 

Island Hospital. 

The ambulance crew irrigated his face and eyes for the duration of the transport. Although the hospital 

was only 4.3 miles away, the trip took 45 to 60 minutes due to snow-covered roads. After being 

decontaminated a second time at the hospital, the injured employee was treated for chemical burns to his 

face, neck, and eyes. He also suffered lacerations to his face, respiratory tract irritation, and a broken 

finger. He remained in the hospital for 14 days and was discharged with diminished sight in both eyes. 

His right eye required multiple surgical procedures and extended treatment over the next year.

2.2 Facility Damage 

The effects of the explosion and fire were largely confined to the vent collection system, with minor 

damage to connected equipment (acid hood, vent hood, scrubber). The CFD cut away a small section of 

the roof above the process area to access the smoldering fire beneath the roof deck. Section 5.0 presents a 

detailed analysis of the explosion and fire damage. 

 

1

 Decontamination involved stripping the employee’s remaining clothes and washing him with soap and water. 
Technic Inc. 08-20-04 

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3.0 Incident Response 

3.1 Employee Evacuation 

According to Technic employees working in the production building at the time of the incident, the fire 

was preceded by a series of loud explosions. Smoke started to fill the building, and the sprinkler alarm 

sounded. The administrative assistant called the CFD at approximately 9:34 am. Employees evacuated to 

the guard station (see Figure 2) for a headcount. Two people were missing. Management personnel, 

including one person with self-contained breathing apparatus (SCBA), entered the building to search for 

missing employees; they found no one and exited. 

3.2 Firefighting 

Within 10 minutes of notification, CFD arrived on scene to find that the building’s sprinkler system was 

operating, and the fire was confined to the new addition. An incident command post was established at 

the corner of Spectacle and Russe Streets. CFD began fighting the fire from the exterior with hoses. 

Technic’s president approached the operations officer to introduce himself and began to discuss the 

situation; however, he was turned away because the officer was busy and did not recognize him as 

someone with pertinent facility information. 

The sprinkler system was operating when the firefighters arrived. However, it was turned off after some 

discussion among the firefighters, Technic management, and the Rhode Island Department of 

Environmental Management (RI–DEM) inspector because of concern that cyanide salt and acid might 

mix to form hydrogen cyanide, a toxic gas. The fire flared up again on mezzanine 1. CFD unrolled the 

hose from the truck parked in the street and put it in position at the overhead door on the east side of the 

storage shed on mezzanine 1. After testing the air for organic vapors, the CFD hazmat team entered the 

building and extinguished the smoldering fires inside the ventilation duct near the scrubber using portable 
Technic Inc. 08-20-04 

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extinguishers. The maintenance supervisor—wearing SCBA and accompanied by firefighters—then 

entered the building to shut down a process unit. 

3.3 Decontamination of Exposed Employees 

The CFD hazmat team set up a decontamination station as a precaution. Eighteen Technic employees 

who may have been exposed to cyanide or other potentially toxic chemicals were decontaminated and 

transported to Rhode Island Hospital for medical evaluation. At the hospital, they were decontaminated a 

second time, examined, and released; no one exhibited any symptoms of chemical exposure. 

3.4 Community Evacuation 

This incident occurred at mid-morning on a weekday, when many residents were away from their homes. 

However, because of concerns about smoke and potential cyanide gas moving in the general direction of 

the nearby community, the CFD incident commander directed the Cranston police to evacuate several 

businesses and residents downwind of the Technic plant. This decision was made approximately 15 

minutes after CFD arrived on scene. At that time, the wind direction was from the northeast at 6 miles 

per hour. One dozen residents were bused to the Cranston Recreation Center, 2 miles away, in 

accordance with evacuation plans previously developed by the Region 8 Local Emergency Planning 

Committee (LEPC). The residents were sheltered for about 4 hours. 
Technic Inc. 08-20-04 

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4.0 Vent Collection System 

4.1 Design, Permitting, and Installation 

In response to Clean Air Act (CAA) emissions standards, in 1990 Technic began a project to design the 

vent collection system to collect process exhausts and transport them to a scrubber. Using process 

descriptions and information supplied by Technic, a design consultant created a preliminary VCS design 

package to collect gases, mists, and vapors.2

 Although not accounted for in its design, the vent collection 

system also collected dusts. Duct size ranged from 36 inches in diameter at the entry to the scrubber to 4 

inches at the process vessels. 

By interviewing the design consultant and reviewing relevant ventilation design information, CSB 

investigators determined that the initial design did not provide capacity for processes that were added at a 

later date. Additions to the vent collection system after the original construction included the following: 

• Ventilation ducts from the process reactors on mezzanine 1 

• Plating tanks in the waste storage area 

• Grinding and packaging operations in the weigh room 

• Tanks in the kettle room 

• Tanks in the silver oxide area. 

In a cover memorandum accompanying the preliminary design package, dated December 21, 1991, the 

consultant asked Technic to clarify several process issues pertaining to hood design and airflow, and fire 

 

2

 The minimum transport velocity required for gases, vapors, and mists is 2,000 feet per minute. The Technic VCS 

design package indicated that the main header duct was designed to this standard. 
Technic Inc. 08-20-04 

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and explosion protection. According to the consultant, Technic did not respond; and the consultant had 

no further involvement with the project. 

Using the preliminary design information, Technic applied to RI–DEM for a minor source construction 

permit on October 24, 1991, for the new vent collection system and scrubber. It was approved on January 

16, 1992. The approval letter advised Technic to notify RI–DEM in writing before making any 

significant physical or operational changes to the system or connected process equipment. 

Using information from the consultant’s preliminary design package, workers from the Pawtucket facility 

fabricated and installed the vent collection system because they had experience constructing and installing 

ventilation ducts for plating systems. Once the ducts were installed, a licensed sprinkler contractor added 

a water sprinkler system inside the larger-diameter duct sections in accordance with the City of Cranston 

mechanical code.3

4.2 System Modifications 

The minor source construction permit for the vent collection system included only the processes on 

mezzanine 2, the Kestner unit, the kettle room, the weigh room, and the metals reclaim areas. Technic 

had made a number of significant changes to the ventilation system since its installation in 1992. These 

modifications were not anticipated by the original design and construction permit4

 and diminished the 

system’s performance capacity. Examples of significant changes include: 

• Connecting seven process reactors and an acid hood on mezzanine 1. 

 

3

 At the time the sprinklers were installed, the City of Cranston had adopted and was enforcing the 1987 edition of 

the Building Officials and Code Administrators, Inc. (BOCA), National Mechanical Code.

4

 In reviewing files, CSB found no evidence of notifications to RI–DEM for proposed changes to the ventilation 

system. When questioned on this point, Technic management personnel explained that they believed the changes 

did not trigger the major modification requirement of RI–DEM air pollution regulations. CSB believed that the 

modifications were major. 
Technic Inc. 08-20-04 

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• Connecting dust-producing delumpers with simple filters and packaging equipment with an inline baghouse in the weigh room.5

• Connecting additional process reactors and blend tanks in the kettle room. 

• Connecting hoods for the three plating tanks in the metals reclaim areas. 

• Removing the in-line baghouse for the delumpers in the weigh room in an attempt to increase 

the dust capture efficiency of the packaging equipment. 

Technic maintenance personnel made these modifications in-house without consulting ventilation design 

or engineering professionals, and without referencing good ventilation practice guidelines. The result was 

a diminished transport velocity that allowed substances to settle out and accumulate inside the vent 

collection system. 

Figure 3 depicts the vent collection system and its connected equipment as it was configured on the day of 

the explosion. This diagram is based on the original design drawings, with added observations and 

information obtained from CSB interviews.6

4.3 Loss Prevention Carrier Review 

In April 2001, the Technic loss prevention insurance carrier recommended the installation of additional 

sprinkler heads inside all VCS ducts of 10-inch diameter or greater. This recommendation was referred to 

senior management but no action was taken. The 10-inch branch duct connected to the acid hood on 

mezzanine 1—which was destroyed in the fire—did not have sprinklers. In addition, the carrier had also 

asked that any future VCS changes be submitted to its field engineering group for review and comment. 

 

5

 CSB was unable to determine the efficiency of these filtering devices or their capacity to prevent dusts from being 

deposited inside the vent collection system. The devices were added in 1992. 

6

 Only the original design drawings were available to CSB; the drawings had not been updated to include 11 years 

of modifications. 
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Figure 3. Vent collection system as of February 7, 2003 

(modifications to original design are shown by dashed lines). 
Technic Inc. 08-20-04 

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From April 2001 until the date of the explosion, additional kettles were added in the kettle room, and the 

baghouse in the weigh room was disconnected in an attempt to increase the duct capture efficiency of the 

packaging equipment. Discussions with the loss prevention carrier revealed that none of these 

modifications were submitted to the carrier for review. 
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5.0 Incident Analysis 

CSB investigated the explosion and fire damage, and analyzed chemical reactions to determine the origin 

and causes of the explosion and fire. 

5.1 Explosion and Fire Analysis 

The explosion likely originated at the vertical exhaust duct connected to tank 8 on mezzanine 2 (Figures 1 

and 3). This section of duct was shattered into small fragments that dispersed in all directions. Figures 4 

through 8 show the extent of the explosion and fire damage to the vent collection system and its 

connected equipment. Table 1 outlines the sequence of events in the explosion and fire. 

Figure 4. Sharp fracture of 4-inch exhaust duct above tank 8. 
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Figure 5. Large fracture of 10-inch branch duct above mezzanine 2 production area. 
Technic Inc. 08-20-04 

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Kettle room

Kestner unit

Weigh room

Technic Inc.

88 Spectacle Street

Cranston, RI

Metals reclaim

areas

Mezzanine 2

Mezzanine 1

Tank 8

(Drawing not to scale or detail.)

Legend:

Fire damage

Acid hood

Explosion

damage

Explosion

Roof VCS damage

junction box

Start of

fire damage

 VCS ducts & direction of airflow

 Damage to VCS ducts

 Damaged process equipment

 Fire & explosion damage area

Scrubber

Figure 6. Depiction of explosion and fire damage, February 7, 2003. 
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 Figure 7. Remains of acid hood on mezzanine 1. 

Figure 8. Collapsed 36-inch-diameter main header at scrubber along east wall. 
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Table 1 

VCS Explosion and Fire Damage Detail 

Location Damage Discussion 

Mezzanine 2 4-inch-dia vertical duct connected to tank 8 

fractured and shattered (Figure 4) 

Explosion originated inside exhaust 

duct, initiated by hammer blow 

Mezzanine 2 10-inch-dia overhead horizontal branch duct 

connecting tanks 5, 6, and 7 (Figure 5) had a 

large crack at main header connection and 

sharp fractures where vertical ducts were 

attached 

Pressure from explosion traveled 

against airflow 

Mezzanine 2 4-inch vertical ducts connected to tanks 5, 6, 

and 7 blown off overhead horizontal branch 

duct 

Damage limited to western overhead 

branch duct 

Area between 

mezzanines 2 

and 1 

4-inch vertical duct connected to silver 

cyanide reactor blown off where it connected 

to horizontal branch header 

Pressure from explosion traveled 

against airflow 

Area between 

mezzanines 2 

and 1 

Hole blown out of 90-degree elbow 

connecting 4-inch vertical duct to silver 

cyanide centrifuge 

Pressure from explosion traveled 

against airflow 

On roof, 

large-diameter 

horizontal branch 

duct to metals 

reclaim areas 

Roof junction box blown out on all sides Pressure from explosion traveled 

against airflow 

Mezzanine 1 Main header duct separated and collapsed 

(Figure 9) 

Second explosion in main header duct; 

subsequent fire melted duct; deposited 

solid material provided fuel for fire 

Mezzanine 1 Westernmost branch duct leading to tanks 

blown out at its connection to main header 

and in several other locations 

Force generated by second explosion 

blew out branch junctions upstream, 

against airflow 

Mezzanine 1 Portions of easternmost branch duct blown 

out at tank junctions (a) 

Force generated by second explosion 

blew out branch junctions upstream, 

against airflow 

Mezzanine 1 Plastic acid hood and its contents totally 

destroyed by fire (Figure 7) 

Fire traveled to acid hood, against 

airflow, and destroyed plastic hood 

and its combustible contents 

Above northernmost end of 

mezzanine 1 

Firefighters opened this section of roof to 

extinguish fire 

Radiant heat from burning acid hood 

charred building roof 

Main header 

from mezzanine 

1 to scrubber 

50 feet of duct melted and collapsed (Figure 

8); hazmat team opened section of duct to 

extinguish smoldering fire 

Duct contained large amount of 

deposited combustible material that 

continued to smolder and flare 

(a) CSB investigators were unable to examine a large portion of the branch duct connecting the acid hood to the main 

header because it was missing. 
Technic Inc. 08-20-04 

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The initial explosion likely ignited fuel (e.g., dusts or accumulated residue) inside the main header. The 

resulting flame moved downstream toward the scrubber, causing at least one additional explosion. The 

presence of shiny, blistered char inside the duct indicates that the fire burned intensely for an extended 

time (Figure 9).7

.

Figure 9. Blistered char inside 36-inch-diameter main header adjacent to mezzanine 1. 

The fire destroyed approximate 50 feet of the main header. No explosion or fire damage was identified 

upstream of mezzanine 2. 

5.2 Chemical Reaction Analysis 

CSB examined all of the process areas connected to the vent collection system and the chemicals used in 

each area. Through years of accumulation of solids (Figure 10) and mixing, many materials could have 

resulted in violent reactions such as the one that caused this incident. CSB evaluated only a sample of 

 

7

 Char is a carbonaceous material that has been burned and has a blackened appearance. When char is shiny with 

interlaced cracks, it is commonly referred to as “alligator char.” 
Technic Inc. 08-20-04 

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those materials that are used in large quantities and might have accumulated in the collection system—

silver nitrate, silver cyanide, sodium hydrosulfite, ammonium citrate, carbon (representing the many 

organic chemicals in the plant), and ammonia. 

Figure 10. Solid deposits in main header duct. 

The injured employee was the only eyewitness who provided CSB with information pertaining to the 

initiating event—namely, that he tapped on the duct with a small hammer, and the explosion immediately 

followed. The CSB investigation focused on substances capable of reacting violently following the 

application of a relatively small amount of energy.8

In collaboration with a reactive chemical expert hired by CSB, OSHA analyzed more than 70 samples 

from locations inside the vent collection system and affected areas, and from the injured employee’s shirt. 

Two scenarios emerged that could account for the initial explosion: 

 

8

 Tapping of the hammer would produce significantly less energy than a lighted cigarette, electrical spark, or open 

flame. 
Technic Inc. 08-20-04 

31 

• A violent reaction of a shock-sensitive material 

• A violent reaction between silver nitrate and another compound. 

Although neither scenario can be conclusively identified as the initiating event, CSB asserts that the 

factors were present to support either reaction. Several other reaction scenarios were considered and 

discarded. 

The International Chemical Safety Card9

 for silver nitrate states that it is a “strong oxidant” and “reacts 

violently with combustible and reducing materials,” forming “shock-sensitive compounds” (International 

Program on Chemical Safety [IPCS], 1993). Silver nitrate is routinely carried into the vent collection 

system together with combustibles and reducing materials. 

5.2.1 Shock-Sensitive Explosive Silver Compounds 

This scenario examines the potential for the presence of shock-sensitive explosive silver compounds 

inside the vent collection system. These compounds are highly unstable materials—even a small amount 

of energy (e.g., the force created by a hammer blow) can cause detonation. 

• Compounds formed from silver nitrate and ammonia—“Many unstable silver compounds are 

known whose decomposition can occur spontaneously and explosively.” Renner (1993) lists 

two compounds—silver azide and silver amide—that could have been formed from silver nitrate 

and ammonia. 

- Silver nitrate is produced daily on mezzanine 1 and in the Kestner unit. It is transferred 

to tank 8 before being used in potassium silver cyanide production. 

 

9

 International chemical safety cards are designed to supply workers with information on the properties of chemicals. 

They are authoritative documents written and extensively peer reviewed by internationally recognized safety 

experts. 
Technic Inc. 08-20-04 

32 

- Ammonia is emitted from two plant processes. It is produced in the reactors on 

mezzanine 2 and during treatment of potassium silver cyanide solutions in the metals 

reclaim areas. 

Although a trace amount of silver azide was identified in one sample taken from inside the vent 

collection system, none was found in any of the ducts involved in the explosion or fire. 

Therefore, it is uncertain whether silver azide played a role in the initial explosion. The force of 

the explosion, subsequent pressure waves, and heat from the fire would likely have initiated and 

consumed any trace amounts of the substance. 

• Metallic silver and silver nitrate—Shock-sensitive explosive silver compounds can form 

interlinked mixtures of metallic silver and silver nitrate (Ennis and Shanley, 1991). Although 

elemental silver was found in several samples—and silver nitrate was routinely introduced into 

the vent collection system—analytical results did not identify any shock-sensitive metallic silver 

or silver nitrate compounds. 

5.2.2 Silver Nitrate Reacting With Another Compound 

There is some evidence to support the possibility that silver nitrate reacted directly with another 

compound: 

• Silver nitrate is a known oxidizer and will react with organic compounds (National Fire 

Protection Association [NFPA], 1998). 

• Silver nitrate is present in the manufacturing process and likely in the vent collection 

system. 

• Various organic compounds have been introduced into the vent collection system over the 

years—many of which were in the form of dusts. 
Technic Inc. 08-20-04 

33 

• Ammonium citrate and sodium hydrosulfite—compounds used in the manufacturing process 

in significant quantities—were tested with silver nitrate using differential scanning and 

accelerating rate calorimeters. In each case, it was determined that a hammer blow could 

initiate the reaction and produce the damage observed in this incident. (See Appendix B.) 

• Elemental silver was found in the vent collection system, though it is not used in the 

manufacturing process in a form likely to be deposited. Elemental silver is produced from 

the reaction of silver nitrate with another organic compound. 
Technic Inc. 08-20-04 

34 

6.0 Analysis of Safety Management Systems 

Process safety management systems help ensure that facilities are designed, maintained, and operated in a 

safe manner (Center for Chemical Process Safety [CCPS], 1989). Although neither the OSHA Process 

Safety Management (PSM) Standard nor the EPA Risk Management Program (RMP) was applicable to 

the Cranston Technic facility, management systems are necessary to ensure that process safety procedures 

are followed. 

In comparing Technic management systems with CCPS and other industry guidance and standards, CSB 

concluded that safety management system failures were the underlying cause of the explosion and fire at 

Technic. CSB reviewed the following safety management systems: 

• Process safety review for projects 

• Management of change (MOC) 

• Process and equipment integrity 

• Emergency planning and response. 

6.1 Process Safety Review for Projects 

Good engineering practices include the use of appropriate codes and standards. As part of the 

engineering process, formal documented process safety review procedures are necessary to ensure an 

effective safety management program and the application of good engineering procedures. Competent 

engineering and safety personnel must be involved to ensure that these procedures explicitly cover the 

identification and mitigation of hazards. Although the Cranston facility had the technical and operational 

personnel to conduct a process safety review, there was no system in place that required the review. 
Technic Inc. 08-20-04 

35 

An initial hazard review should be conducted during the early stages of a project to identify incompatible 

materials and the need to separate them. CSB found no evidence of such a review for the vent collection 

system, though the company asserts that there were several safety discussions during the VCS project. 

Because of the failure to follow a formalized process safety review procedure, Technic installed a vent 

collection system that: 

• Did not meet regulatory or industry good practice guidelines 

• Was not capable of being modified without degrading performance 

• Allowed incompatible chemicals to accumulate in the duct and mix. 

• Did not address the concerns of the insurance carrier and the ventilation design contractor. 

6.2 Management of Change 

MOC is a system of managing process system changes (e.g., chemistry, equipment, procedures, or 

organization) to prevent catastrophic consequences. MOC allows for the identification of hazards so that 

they can be limited or mitigated. Even a minor process change may trigger a formal process hazard 

review to identify and evaluate its effects. Process hazards created by such changes must be documented 

and mitigated through engineering or work-practice controls. 

Technic did not conduct process hazard reviews in conjunction with process changes. Significant 

modifications made to the vent collection system over its 11 years of operation severely degraded 

transport velocity and introduced a host of chemicals—including dusts—that were not evaluated for 

compatibility. A process hazard review would likely have identified silver nitrate and organic compounds 

as incompatible, signaling the need for separate ventilation control systems. 
Technic Inc. 08-20-04 

36 

For example, the vent collection system was not designed with enough velocity to transport dusts 

generated in the weigh room to the scrubber; it was designed only for gases, vapors, and mists. In-house 

maintenance personnel installed filtering devices near the dust-generating equipment.10 However, the 

large amount of accumulated debris in the main VCS header—downstream of the weigh room branch 

duct—indicates that the filtering devices were either improperly sized or inadequately maintained. 

Process modifications and duct additions to the ventilation system over the years further deteriorated 

transport velocity—which was inadequate for dusts to begin with. The large amounts of dust that 

accumulated were available to react with other substances passing through the system and also provided 

fuel for the February 7 fire. 

In December 2002, OSHA cited Technic for employee overexposure to silver dusts in the weigh room. 

After receiving the citation, Technic attempted to eliminate these exposures by removing the baghouse 

that captured dusts generated during packaging and weighing. Technic management told CSB that the 

baghouse created a drag on the system; by removing it, they expected the capture velocity to improve 

enough to reduce employee exposure to within acceptable limits. 

This change did not trigger a process hazard review by Technic management. Silver levels in the silver 

recovery area—which handles effluent from the scrubber—immediately spiked, signaling a significant 

increase in silver-containing dusts being introduced into the vent collection system.11 This result was 

likely due to removal of the filters. 

 

10 A baghouse was installed 10 to 15 feet downstream of the weigh room, and household heating system filters were 

installed approximately 5 feet downstream of the delumpers. 

11 There is some controversy as to the relationship between disconnecting the baghouse and the spike in silver levels. 

The Technic waste treatment technician claims that he noticed the spike immediately, which was confirmed by 

Technic management. A review of the scrubber water treatment logs, however—though indicating a noticeable 

increase seemingly associated with disconnect of the baghouse—also reveals that in several periods while the 

baghouse was connected and in use, there were also spikes in silver effluent. It is worth noting that these spikes 

may have been due to inconsistent baghouse maintenance or other operator-related factors. 
Technic Inc. 08-20-04 

37 

6.3 Process and Equipment Integrity 

The objective of a process and equipment integrity program is to identify process and equipment defects 

that could result in a catastrophic failure. A comprehensive program will ensure the safe operation of 

processes and equipment throughout their life cycles. Technic had some elements of a process and 

equipment integrity program on other equipment, but there was no formal, scheduled, and documented 

inspection and preventive maintenance program for the vent collection system. 

Because the actual performance of the vent collection system was not measured, the facility had no 

baseline—other than theoretical values in the original design drawings—against which to measure VCS 

performance. The collection system had no inspection ports or cleanout doors, and it had not been 

cleaned since 1996. These design features—combined with a routine inspection and maintenance 

program—would have facilitated the detection and elimination of accumulated material that CSB 

observed and believes likely contributed to the initial explosion and fueled the fire. In summary, Technic 

had no established inspection, cleaning, or maintenance program for the vent collection system. 

6.4 Emergency Planning and Response 

Facilities that handle highly hazardous materials should be designed with multiple layers of safety 

protection to ensure the safety of workers and the surrounding community (CCPS, 1995; Figure 11). On 

the day of the incident, the inner layers of protection at Technic failed (i.e., design and engineering, and 

process and safety controls), causing the facility to rely on mitigation and emergency response. Although 

the inner layers of protection offer more prevention than the outer layers, all layers are necessary. 
Technic Inc. 08-20-04 

38 

Figure 11. Layers of protection in a modern chemical plant. 

6.4.1 Facility Emergency Planning and Response 

6.4.1.1 Emergency Plan

Emergency plans are mandatory under both OSHA and EPA12 regulations; generally accepted industry 

guidance is available from sources such as CCPS (1995). Prior to the incident, Technic had provided the 

municipal fire department (CFD) with an emergency plan for its facility. However, as the incident 

revealed, the plan did not stand well on its own and did not meet minimum regulatory requirements. 

Prior coordination and rehearsal by Technic and CFD would have revealed the plan’s shortcomings and 

likely improved response. 

 

12 The OSHA standard for emergency action plans is codified at 29 CFR 1910.38(a)(2). EPA requirements are 

codified in the Emergency Planning and Community Right-to-Know Act of 1986 (EPCRA), 40 CFR 350–372. 

Community emergency response 

Plant emergency response 

Mitigation (e.g., sprinklers, 

chemical showers) 

Safety controls and alarms 

Design 

Process controls 
Technic Inc. 08-20-04 

39 

For instance, the emergency plan did not describe the exact quantities and locations of cyanides and acids, 

or the provisions taken by Technic to safeguard them. CFD may have responded less aggressively to the 

fire than it otherwise would have because the firefighters feared that hydrogen cyanide—an extremely 

toxic gas—could be generated if sprinkler water accumulating on the floor somehow allowed the mixing 

of cyanide salt and acids. The sprinkler system was perhaps shut off prematurely. If the plan had 

specified that hazardous materials were invulnerable to firefighting because they were separated or 

contained (as was the case at Technic)—or if the plan had been rehearsed or coordinated in advance—

CFD may have taken more aggressive action sooner. 

Likewise, the emergency plan did not outline important roles and responsibilities—such as the Technic 

point of contact, the incident commander, the person responsible for notifications, or the person 

responsible for corrective action (e.g., shutting down critical processes and ensuring that all personnel are 

counted for). As discussed in Section 3.2, the CFD operations officer did not know who was in charge at 

Technic. Planning, coordination, and training can help minimize stress and confusion by removing 

uncertainty and improving confidence. 

6.4.1.2 Search and Rescue 

The employee evacuation was disorganized and confusing, which resulted in unnecessary, hazardous 

actions by Technic employees. A preliminary head count revealed that two employees were missing. A 

supervisor donned SCBA and reentered the process building to search for them. This was in violation of 

established OSHA regulations pertaining to fire prevention and respiratory protection, as discussed below. 

OSHA considers search and rescue conducted during a fire to be advanced firefighting, which is 

addressed in the Fire Brigade standard (29 CFR 1910.156). Technic did not have a fire brigade, or the 

requisite equipment or training to carry out its functions. Technic personnel were trained only in the use 

of portable fire extinguishers to put out incident stage fires (29 CRF 1910.157). In addition, the 

procedures for the use of SCBA in firefighting situations—outlined in the OSHA Respiratory Protection 
Technic Inc. 08-20-04 

40 

standard (29 CFR 1910.134 (g) (3))—were not followed. These procedures require at least four persons 

(two to enter and two as standby) to be equipped with SCBA when entry is made into an unknown 

atmosphere (e.g., immediately dangerous to life or health [IDLH]) during firefighting. Periodic 

evacuation drills would have likely resulted in employees being accounted for and thus precluded 

unnecessary search and rescue efforts. 

6.4.2 Community Emergency Planning and Response 

According to EPA, no one was exposed to hazardous substances. CFD initiated community evacuation at 

the first sign of any hazards, and all residents in the zone of danger were successfully evacuated to a point 

of safety. CFD prepared an annual emergency plan for Technic, which was carried on its fire trucks. The 

community emergency response was consistent with established guidelines (Federal Emergency 

Management Agency [FEMA], 2002). 

The Cranston Fire Chief is also chairman of the Rhode Island District 8 LEPC. The purpose of the LEPC 

is to plan and coordinate community protection against catastrophic chemical releases based on EPCRA 

requirements (see Section 7.1.5). The fire chief told CSB investigators that, based on Technic’s chemical 

inventory submissions, it is among the top 10 facilities of concern within District 8. 

Because of other priorities such as homeland security, the LEPC had not held public meetings in a year, 

was behind in its EPCRA-required community emergency response plan, and had never conducted an 

emergency response exercise with Technic. Specifically, the community plan lacked facility-specific 

information for an adequate emergency response, such as location of chemicals, hazards of mixing 

chemicals, and details on the containment and segregation of chemicals. The fire chief told CSB 

investigators that these deficiencies were due to a lack of funding, personnel, and computer equipment—

and to conflicting national priorities for terrorism planning among some LEPC members (e.g., police, fire 

department, hospitals). The involvement of the LEPC and CFD in the planning process, as required, 

would have improved emergency response. 
Technic Inc. 08-20-04 

41 

7.0 Regulatory and Industry Standards Analysis 

CSB reviewed environmental, safety, and health guidance applicable at the time (1992) Technic installed 

the vent collection system. The review included government regulations, local building and mechanical 

codes, and industry consensus standards (guidelines) relevant to the explosion and fire. CSB also looked 

at currently applicable guidance to determine if revisions are warranted. Only the guidance applicable to 

the Technic incident is discussed below. 

7.1 Environmental, Safety, and Health Regulations 

7.1.1 OSHA Process Safety Management 

The OSHA PSM Standard (29 CFR 1910.119) is a systematic approach to process safety and the 

prevention of catastrophic incidents. It requires adherence to 14 elements of good safety management for 

processes containing specific chemicals or flammables if they are present in quantities greater than 10,000 

pounds. The PSM Standard does not apply to Technic because listed chemicals are not present at the 

required threshold quantities. 

7.1.2 EPA Risk Management Program 

The EPA RMP is a product of the CAA Amendments of 1990. In many ways, RMP mirrors the PSM 

Standard. However, RMP focuses on protecting the public and the environment from offsite 

consequences, while PSM addresses consequences for workers. RMP does not apply to Technic because 

listed chemicals are not present at the required threshold quantities. 
Technic Inc. 08-20-04 

42 

7.1.3 OSHA Ventilation Standards 

Although OSHA has no general safety or health regulations that apply to vent collection systems, it does 

have specific ventilation regulations for dipping and coating operations.13 These regulations apply to the 

Technic metals reclaim areas, which are connected to the ventilation system. They require separate 

exhaust systems to prevent mixing of incompatible materials, as well as periodic inspection and 

maintenance. 

For other types of ventilation systems, OSHA relies on the general duty clause (GDC) to enforce safe use. 

This clause—found in Section 5(a)(1) of the Occupational Safety and Health Act, promulgated in 1970— 

requires employers to eliminate recognized hazards in their workplaces, even when there is no specific 

OSHA rule or standard. According to OSHA, employers must take whatever abatement actions are 

feasible to eliminate hazards. 

For the February 7 explosion and fire, OSHA cited Technic:14

• For its actions that created fire and explosion hazards within the vent collection system, under 

the GDC. 

• For not providing independent exhaust systems for tanks in the silver recovery area, under the 

dipping and coatings standard. 

7.1.4 Clean Air Act 

Under authority of the CAA of 1970, RI–DEM administers a new source permitting program for air 

pollution sources like the vent collection system. This State program requires applicants to apply for a 

permit if they create a new source that generates any one of the EPA-listed hazardous air pollutants, or if 

 

13 29 CFR 1910.123, Dipping and Coating Operations: Coverage and Definitions; and 29 CFR 1910.124, General 

Requirements for Dipping and Coating Operations. 

14 Citations were issued on July 28, 2003, and settled on August 11, 2003. 
Technic Inc. 08-20-04 

43 

they intend to significantly modify an existing pollution source. The program focuses on compliance 

with air emissions regulations and does not address process safety hazards from incompatible chemical 

mixing. 

RI–DEM conducted a technical review of the design drawings—but only from the perspective of 

emissions reduction. RI–DEM also conducted a post-installation site visit, but did not attempt to identify 

process changes or minor variations between design and actual installation. 

7.1.5 Emergency Planning and Community Right-to-Know Act 

The Superfund Amendments and Reauthorization Act (SARA), Title III, was enacted in 1986. EPCRA 

codifies EPA requirements—which call for each state governor to set up a State Emergency Response 

Commission, which establishes LEPCs. 

LEPCs are charged with developing community emergency response plans for incidents involving 

hazardous materials. They also routinely coordinate chemical release incident exercises and facility visits 

so that emergency response team members become familiar with the unique challenges of each facility. 

These activities help pinpoint plan deficiencies and promote confidence among team members and plant 

management. 

As noted in Section 6.4.2, the Rhode Island Region 8 LEPC has been delayed in implementing the 

requirements of its community emergency response plan. 

7.2 Mechanical Code 

A mechanical code requires engineers and design professionals to incorporate safety features into the 

design, engineering, and construction of mechanical systems installed inside buildings. The State of 

Rhode Island had a mechanical code in effect when the Technic consultant designed the vent collection 

system, but the code did not prohibit incompatible reactive chemical mixing or require designers to 
Technic Inc. 08-20-04 

44 

ascertain whether such mixing might occur.15 The City of Cranston building department—the local 

agency that reviews and enforces the code—reviewed the Technic VCS design, but relied heavily on the 

permit review conducted by RI–DEM. Like RI–DEM, the city did not assess chemical compatibility. 

In 2002, the State of Rhode Island adopted a mechanical code that requires incompatible materials to be 

exhausted through separate exhaust systems.16 Although this requirement provides much needed 

guidance to designers and engineers, and to building department officials and building inspectors who 

review VCS designs and installations, it has not been applied retroactively. 

7.3 Consensus Standards 

Consensus standards are voluntary compliance guidelines created by balanced working groups of 

interested and diverse experts and stakeholders. NFPA, the American National Standards Institute 

(ANSI), and the International Standards Organization (ISO) are examples of respected standard-making 

organizations. Although consensus standards are generally nonmandatory, they are often referred to (or 

adopted) in regulations and codes, and are used extensively throughout industry. 

Rhode Island has adopted the Uniform Fire Code (NFPA 1), which incorporates NFPA 91 and NFPA 654 

by reference. There are currently four widely used consensus standards pertaining to vent collection 

systems: 

• NFPA 91, Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and 

Noncombustible Particulate Solids: NFPA 91 applies to all exhaust systems—except those 

designed for combustible particulates—and is intended to provide life and property protection 

against fires and explosions. This standard specifically prohibits incompatible materials from 

 

15 As noted in Section 4.1 of this report, Cranston used the BOCA National Mechanical Code, 1987 edition. 

16 The Rhode Island Building Code Standards Committee adopted the International Code Council (ICC) 

International Mechanical Code on September 1, 2002. Section 510.5 addresses incompatible materials. 
Technic Inc. 08-20-04 

45 

being mixed. Other requirements of the standard are access doors in horizontal ducts every 12 

feet; automatic fire extinguishing systems inside ducts; and testing, inspection, and maintenance 

of these systems at regular intervals (NFPA, 1999). NFPA 91 is deficient in that it does not 

reference appropriate methods for such evaluation, such as ASTM E-2012-0. 

• NFPA 654, Prevention of Fire and Dust Explosions From the Manufacturing, Processing, and 

Handling of Combustible Particulate Solids: NFPA 654 supplements NFPA 91 by specifically 

addressing hazards associated with systems that handle combustible dusts. It requires 

conformance with all the provisions of NFPA 91, in addition to preventive measures to eliminate 

the accumulation of materials in ducts and the propagation of explosions through the duct 

system (NFPA, 2000). 

• ANSI Z9.2, Design and Operation of Local Exhaust Ventilation Systems: ANSI Z9.2 applies to 

vent collection systems used to control employee exposures to harmful substances. It requires 

that separate exhaust systems be used when incompatible material mixing may result in health or 

explosion hazards, or destructive corrosion (ANSI, 1991). ANSI Z9.2 is deficient in that it does 

not reference appropriate methods for such evaluation, such as ASTM E-2012-0. 

• Industrial Ventilation: A Manual of Recommended Practice: This American Conference of 

Governmental Industrial Hygienists (ACGIH) manual is widely used to design and evaluate new 

and existing industrial ventilation systems. Although it instructs designers to take preliminary 

steps to ascertain toxicity, and physical and chemical characteristics, it does not specifically call 

for consideration of chemical compatibility (ACGIH, 2001). 

The mechanical code and some consensus standards underscore the need to identify incompatible 

materials. However, none of these resources outlines a method to conduct such analyses. The CSB 

hazard study Improving Reactive Hazard Management (USCSB, 2002) suggests using ASTM E 2012-00, 
Technic Inc. 08-20-04 

46 

Standard Guide for the Preparation of a Binary Chemical Compatibility Chart (American Society for 

Testing and Materials [ASTM], 2003). 

The ASTM guide provides a systematic method for determining whether two chemicals will react with 

one another under a stated scenario. If used during the planning and design phases, or in conjunction with 

a process hazard review, this particular binary evaluation system will often identify incompatibility 

hazards that would otherwise be missed. Although the method applies only to two materials, it can be 

adapted to include multiple materials. Moreover, in addition to providing a structure for incompatibility 

analysis, it documents the steps necessary to identify and evaluate hazards. It also can be used to 

demonstrate to regulatory agencies that such an analysis has been conducted. 

7.4 Loss Prevention Guidance 

The Technic loss prevention insurance carrier published a property loss prevention data sheet that lists 

recommendations for industrial exhaust systems (FM Global, 2000). It addresses the following: 

• Transport velocities 

• Materials of construction 

• Sprinkler protection 

• Incompatible materials 

• Inspection and maintenance. 

Although this data sheet was not available during design and construction of the vent collection system, it 

was presented to Technic prior to the incident (April 2001) in support of a recommendation to install 

additional sprinkler heads in the VCS ducts. Receipt of the data sheet should have signaled the need to 

evaluate fire and explosion hazards by conducting a process safety review. Technic took no action, 
Technic Inc. 08-20-04 

47 

explaining to CSB that it believed the system was performing adequately. Emissions were being reduced 

to permit levels, and there had been no prior incidents that signaled potential safety hazards. 
Technic Inc. 08-20-04 

48 

8.0 Root and Contributing Causes 

8.1 Root Causes 

1. Technic did not conduct a process safety review as a part of the engineering process to identify 

and evaluate the hazards associated with installing a vent collection system to handle the 

exhausts from multiple processes. 

• The ventilation consultant hired to design the system posed several questions to Technic 

regarding the materials it intended to introduce into the system. Technic did not respond to these 

questions and did not use the consultant during the remaining phases of the project. 

• Despite having chemists on staff, Technic did not take advantage of their expertise in assessing 

process chemical compatibility. 

• Such a review would have likely included a process hazard analysis to identify and evaluate 

reactive chemical hazards. It would have also involved competent reviewers to evaluate and 

verify the design prior to and after installation. 

2. Technic did not identify and evaluate the hazards created by changes to facility processes and 

equipment (i.e., management of change). 

• Technic maintenance personnel modified the vent collection system without applying good 

engineering practices. Significant changes were made to the vent collection system that were not 

envisioned in the original design and deteriorated its performance. Such modifications were not 

accompanied by a design and engineering review, a process hazard analysis, or before-and-after 

performance testing to ensure that the system was operating as intended. The relative effects of 

these modifications were not evaluated against baseline performance measurements. 
Technic Inc. 08-20-04 

49 

• Technic did not take advantage of the expertise and engineering review services of its loss 

prevention insurer. 

8.2 Contributing Causes 

1. Technic did not have process and equipment integrity procedures or training to inspect or 

maintain the vent collection system. The system was built without cleanout doors and was not 

capable of easily being inspected. It had not been cleaned since 1996. 

2. Neither Technic nor the Cranston Fire Department (CFD) adequately planned for this type of 

emergency. 

• The emergency plan Technic provided to CFD did not include key facility information, and CFD 

was not familiar with the facility or its managers. This led to confusion and uncertainty during 

the response and likely accounted for the severity of the fire damage. 

• Neither Technic nor CFD had ever conducted a chemical release exercise. Technic was unable to 

account for all its employees, which led a supervisor to take risky actions to reenter the building. 
Technic Inc. 08-20-04 

50 

9.0 Recommendations 

Technic Inc.

1. As a part of the engineering process, implement formal process safety review procedures for 

projects involving chemical processes—including the vent collection system. Incorporate a 

process hazard analysis, reactive chemical hazard evaluation, and design evaluation consistent 

with applicable codes and standards. (2003-08-I-RI-R1) 

2. Implement a management-of-change program and ensure that reviews are conducted for any 

proposed changes to the vent collection system and its connected processes. (2003-08-I-RI-R2) 

3. Implement a preventive maintenance program for the vent collection system that includes regular 

inspections training and troubleshooting. (2003-08-I-RI-R3) 

4. Work with the Cranston Fire Department to improve the facility’s emergency response plan, 

including emergency response procedures and interface with the surrounding community. Submit 

the plan to the fire department for review. (2003-08-I-RI-R4) 

National Fire Protection Association (NFPA) 

Revise the appendix of NFPA 91, Standard for Exhaust Systems for Air Conveying of Vapors, Gases, 

Mists, and Noncombustible Particulate Solids, emphasizing the need to evaluate potential 

incompatibilities when dusts, fumes, or vapors are intermixed in vent collection systems to ensure that 

they do not result in fire or explosion hazards, or destructive corrosion. Reference appropriate methods 

for such evaluations, such as the ASTM E 2012-00 standard. (2003-08-I-RI-R5)
Technic Inc. 08-20-04 

51 

American Industrial Hygiene Association (AIHA) 

Revise the appendix of ANSI Z9.2, American National Standard Fundamentals Governing the Design 

and Operation of Local Exhaust Systems, emphasizing the need to evaluate potential incompatibilities 

when dusts, fumes, or vapors are intermixed in local exhaust ventilation systems with common headers to 

ensure that they do not result in fire or explosion hazards, or destructive corrosion. Reference appropriate 

methods for such evaluations, such as the ASTM E 2012-00 standard. (2003-08-I-RI-R6) 

American Conference of Governmental Industrial Hygienists (ACGIH) 

Update the preliminary steps in the chapter on exhaust system design in the next revision of the Industrial 

Ventilation Manual, emphasizing the need to evaluate potential incompatibilities between dusts, fumes, or 

vapors that are likely to be intermixed in main header ducts of a ventilation system to ensure that they do 

not result in fire or explosion hazards, or destructive corrosion. Reference appropriate methods for such 

evaluations, such as the ASTM E 2012-00 standard. (2003-08-I-RI-R7) 

By the 

U.S. Chemical Safety and Hazard Investigation Board 

Carolyn W. Merritt 

 Chair 

 John S. Bresland 

 Member 

 Rixio Medina 

 Member 

Gerald V. Poje, Ph.D. 

 Member 

 Gary Lee Visscher 

 Member 

August 20, 2004
Technic Inc. 08-20-04 

52 

10.0 References 

American Conference of Governmental Industrial Hygienists (ACGIH), 2001. Industrial Ventilation: A 

Manual of Recommended Practice, Sections 5.1–5.2. 

American National Standards Institute (ANSI), 1991. Design and Operation of Local Exhaust Ventilation 

Systems, ANSI Z9.2. 

American Society for Testing and Materials (ASTM), 2003. Standard Guide for the Preparation of a 

Binary Chemical Compatibility Chart, ASTM E 2012-00. 

Building Officials and Code Administrators International, Inc. (BOCA), 1987. National Mechanical 

Code. 

Bodurtha, F. T., 1976. “Explosion Hazards in Pollution Control,” Loss Prevention, Vol. 10, American 

Institute of Chemical Engineers (AIChE). 

Bretherick, Leslie, P. G. Urben, and Martin J. Pitt, 1999. Bretherick’s Handbook of Reactive Chemical 

Hazards, Sixth Edition, Vol. 1, Butterworth-Heinemann. 

Center for Chemical Process Safety (CCPS), 1995. Guidelines for Technical Planning for On Site 

Emergencies, AIChE. 

CCPS, 1993, Guidelines for Engineering Design for Process Safety, AIChE. 

CCPS, 1989. Technical Management of Chemical Process Safety, AIChE. 

Center for Waste Reduction Technology (CWRT), 2003. Practical Solutions for Reducing Volatile 

Organic Compounds and Hazardous Air Pollutants, AIChE. 
Technic Inc. 08-20-04 

53 

Clark, D. G., and R. W. Syvester, 1996. “Ensure Process Vent Collection System Safety,” Chemical 

Engineering Progress, January 1996, pp. 65–77. 

Ennis, John L., and, Edward S. Shanley, 1991. “On Hazardous Silver Compounds,” Journal of Chemical 

Education, Vol. 68, January 1991, p. A6. 

Factory Mutual Insurance Company (FM Global), 2000. Industrial Exhaust Systems, Property Loss 

Prevention Data Sheet 7-78. 

Federal Emergency Management Agency and U.S. Fire Administration (FEMA–USFA), 2003. Risk 

Management Planning for Hazardous Materials: What It Means for Fire Service Planning, USFATR-124, January 2003. 

FEMA, 2002. Planning Protective Action Decision-Making: Evacuate or Shelter-in-Place? prepared by 

Oak Ridge National Laboratory, ORNL/TM-2002/144, June 2002. 

International Code Council (ICC), 2000. International Mechanical Code, Section 510.5. 

International Program on Chemical Safety (IPCS), 1993. International Chemical Safety Card, Silver 

Nitrate, www.cdc.gov/niosh/ipcsneng/neng1116. 

National Fire Protection Association (NFPA), 2000. Prevention of Fire and Dust Explosions From the 

Manufacturing, Procesing, and Handling of Combustible Particulate Solids, NFPA 654. 

NFPA, 1999. Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and 

Noncombustible Particulate Solids, NFPA 91. 

NFPA, 1998. Liquid and Solid Oxidizers, Vol. 7, Standard 430. 
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Nichols, F. P., 1998. “Design of Vent Collection and Destruction Systems,” International Symposium on 

Runaway Reactions, Pressure Relief Design, and Effluent Handling, G. A. Melhem and H. G. Fisher, 

eds., AIChE. 

Ogle, R. A., A. R. Carpenter, and D. Morrison, 2004. “Lessons Learned From Fires and Explosions 

Involving Air Pollution Control Systems,” 38th Annual Loss Prevention Symposium, AIChE. 

Ozog, H., and W. J. Enry, 2000. “Safety Hazards Associated with Air-Emission Controls,” Process 

Safety Progress, Vol 19, Spring 2000, pp. 25–31. 

Renner, H., 1993. “Silver, Silver Compounds, and Silver Alloys,” Ullman’s Encyclopedia of Industrial 

Chemistry, Vol. A24, VCH Publishers, p. 138. 

 Shanley, Edward S., and John L. Ennis, 1991. “The Chemistry and Free Energy of Formation of Silver 

Nitride,” I&EC Research, Vol. 30, pp. 2503–2506. 

U.S. Chemical Safety and Hazard Investigation Board (USCSB), 2002. Hazard Investigation, Improving 

Reactive Hazard Management, Report No. 2001-01-H, December 2002. 

U.S. Environmental Protection Agency (USEPA), 1998. Air Pollution Operating Permit Program 

Update, No. 451-K-98-002, February 1998. 
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APPENDIX A: Technic Production and Processes 

Appendix A describes the processes connected to the vent collection system and associated chemicals, 

and their status immediately prior to the explosion. 

A.1 Silver Nitrate 

Silver nitrate is produced using the Kestner unit (an enclosed vessel) and three jacketed batch reactors 

located on mezzanine 1. The vent collection system transports entrained silver nitrate, nitrogen oxides 

(NOx), nitric acid vapor, and water vapor. 

• Kestner unit: Interviews with employees revealed that during occasional process upsets, fumes 

from this distillation vessel overwhelmed the vent collection system and vented into the plant. 

In-house maintenance personnel connected the Kestner unit to the vent collection system as 

shown in Figure A-1. This unit was in full operation on the day of the explosion. 

• Mezzanine 1: Employees stated that on occasion dark red smoke overwhelmed the vent 

collection system and escaped through the loose-fitting tank access door into the plant (Figure 

A-2). On the day of the explosion, three batches of silver nitrate were being held on mezzanine 

1 for future use, but none were being processed. 
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Figure A-1. Kestner unit exhaust ventilation. 

Figure A-2. Silver nitrate reactor on mezzanine 1 with open tank door 

 (following explosion and fire). 
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A.2 Silver Cyanide/Potassium Silver Cyanide 

Silver cyanide is produced in a reactor located on the ground level between mezzanines 1 and 2. This 

process is manually operated without any process alarms, interlocks, or automatic shutoffs. It produces 

very little gas or vapor because it is not heated and does not produce heat during the reaction; however, it 

is connected to the vent collection system. No silver cyanide was being produced on the day of the 

incident. 

Potassium silver cyanide is produced in three batch reactors on mezzanine 2. The solution used in this 

process is reused approximately 15 times. It is prepared for reuse by heating and evaporating in jacketed 

reactors. Evaporation concentrates the silver cyanide and reduces the batch volume so that more reactants 

can be added. As the solution nears the end of its usefulness, it starts to exhibit an ammonia odor that 

signals the need to discard it and mix up a new batch. Discarded solutions are taken to the metals reclaim 

areas for silver reclamation and treatment. 

This process generates silver cyanide, water vapor, potassium cyanide vapor, and ammonia vapor—all of 

which are extracted by the vent collection system. No batches of potassium silver cyanide were being 

processed or evaporated on the day of the explosion. 

A.3 Plating Solution Mixtures (Kettle Room) 

The kettle room is used to process made-to-order batches of some 1,700 different plating-related 

chemicals. It contains 20 jacketed process kettles, ranging from 60 to 1,000 gallons; and four product 

mixing and storage tanks, ranging from 500 to 1,000 gallons. Each of the kettles is used for a variety of 

batch recipes. All of the kettles and mixing tanks are connected to the vent collection system. 

The most common chemicals associated with the most frequently produced batches include ammonium 

citrate, sulfonates, ethers, aldehydes, aliphatics, amines, alcohols, and various salts and acids. On the day 

of the incident, three small batches of plating chemicals were being prepared in the kettle room. 
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A.4 Other Connected Process Areas 

The following process areas are located in the older portion of the facility and were connected to the vent 

collection system during the 1990 expansion. 

A.4.1 Metals Reclaim Areas 

Technic recovers precious metals from various waste materials in two metals reclaim areas. These wastes 

include spent solutions and discarded electronic components from other Technic plants. In addition, 

Technic receives spent plating solutions that are classified and shipped as hazardous waste under EPA 

and U.S. Department of Transportation (DOT) guidelines. All tanks are equipped with exhaust hoods 

directly connected to the vent collection system. 

A.4.1.1 Silver Electroplating

During the silver electroplating1 process, solutions are chemically treated with a formaldehyde solution to 

remove residual cyanide.2

 Once the formaldehyde is added, the solution is heated to approximately 180 

degrees Fahrenheit (oF). The electrodes are then energized and the solution sits undisturbed overnight 

with the ventilation system running. Each morning, at the beginning of the shift, these solutions are 

pumped back into drums for disposal, and the silver is harvested from the copper cathodes. Technic 

performs silver electroplating daily in four to six tanks. 

 

1

 At Technic, electroplating is accomplished by passing a direct electrical current through the spent solution; the 

dissolved silver attaches to copper plates (cathodes) submerged in the solution. 

2

 Para-formaldehyde prills are a powdered form of formaldehyde added to cyanide-containing solutions to reduce 

the threat of generating hydrogen cyanide gas (which is extremely toxic) and to make the solutions less hazardous 

for disposal. 
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A.4.1.2 Gold Precipitating

Waste gold-plating solutions are chemically treated to prevent toxic gas generation and to precipitate the 

dissolved gold out of solution.3

 Once pretreated, sodium hydrosulfite is added to the solution to activate 

the precipitation process. The solution is then allowed to sit overnight. At the beginning of the next shift, 

the reacted cyanide is skimmed off and the remaining solution is pumped into barrels for disposal. The 

gold is then pumped from the bottom of the tank. 

A high pH cyanide solution is used to strip the gold from plated electronic circuitry. This process creates 

potassium gold cyanide, which is then put through the gold precipitation process (described above) to 

recover the dissolved gold. 

A.4.2 Cyanide Salt De-lumping and Packaging (Weigh Room) 

Silver cyanide and potassium silver cyanide pastes produced on mezzanines 1 and 2 are dried in two 

ovens in this area.4

 After drying to the consistency of caked powder, the materials are de-lumped in 

grinders and then poured into 55-gallon drums equipped with auger-type dispensers for packaging. The 

exhausts from the grinders pass through filters that exhaust to the vent collection system. The exhaust 

vents from the dispensers pass through an in-line baghouse (removed in December 2002) connected to the 

vent collection system. 

 

3

 Potassium hydroxide flakes are added to stabilize the pH of the solution and to prevent the generation of hydrogen 

cyanide and chlorine gases. 

4

 Oven exhausts are not connected to the ventilation system. 
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APPENDIX B: Calorimetric Testing 

Under contract to CSB, ioMosaic Corporation, Salem, New Hampshire, conducted three accelerating rate 

calorimetry (ARC) tests to explore the stability and chemical reaction characteristics of silver nitrate with 

other organics that were present in the facility in large quantities and could have been present in the vent 

collection system: 

• Sodium hydrosulfite/silver nitrate, equimolar mixture. 

• Ammonium citrate/silver nitrate, equimolar mixture. 

• Carbon/silver nitrate, 1.5:1 molar ratio. 

The ARC was selected as a test instrument because of its ability to detect exothermic activity at low selfheating rates in a near-adiabatic test environment. 

The ARC test data indicate that the sodium hydrosulfite/silver nitrate was the most sensitive mixture. 

Small levels of self-heating were detected at 35 degrees Celsius (oC), as evident by the ARC trace. 

Mixture 3 had the highest onset temperature (170oC; less sensitive than mixture 1), but once initiated led 

to an actual explosion that destroyed the test cell. Mixture 2 onset was detected at 130oC. The data 

clearly show that a violent reaction between silver nitrate and other organics can be initiated at 

temperatures as low as 35oC. Although these tests were conducted in a near adiabatic environment, the 

results are directly applicable to the Technic vent collection system because the reacting materials could 

have been present in the system under inertial confinement. 
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APPENDIX C: Causal Factors Diagram 
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Blast knocks

employee to floor of

mezzanine 2

Employee is injured

and staggers off

mezzanine

Employee seeks

eyewash

BRANCH A

Employee injuries

Employee moves to

guard shack

Waited until

paramedics arrived

Paramedics treat

victim

Employee give

statement to RI–

Told RI–DEM t

hammer tappi

produced explo

at tank 8

Paramedics

decontaminate victim,

use saline-soaked

cloth on face

Medical treatment

provided by

paramedics LTA

One broken eyewash

delays employee in

flushing eyes,

splashes water on

eyes at sink in the

laboratory
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