Health Hazard Evaluation Report 2014-0042-3216 Page 1

Evaluation of Exposures and a Potential 

Hydrogen Sulfide Release Event at an Aircraft 

Engine Services Facility, West Virginia

Report No. 2014-0042-3216

July 2014

Jenna L. Armstrong, PhD

Kristin J. Cummings, MD, MPH

Randy Boylstein, MS, REHS

Jason Ham, PhD

David Blackley, DrPH

U.S. Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health
Page 2 Health Hazard Evaluation Report 2014-0042-3216

Contents

Highlights...............................................i

Abbreviations ..................................... iii

Introduction......................................... 1

Assessment .......................................... 2

Results .................................................. 2

Discussion ............................................ 2

Conclusions.......................................... 3

Recommendations............................... 3

Appendix.............................................. 4

References............................................ 6

Acknowledgements............................. 9

The employer is required to post a copy of this report for 30 days at or near the 

workplace(s) of affected employees. The employer must take steps to ensure 

that the posted report is not altered, defaced, or covered by other material.

The cover photo is a close-up image of sorbent tubes, which are used by the HHE

Program to measure airborne exposures. This photo is an artistic representation that may

not be related to this Health Hazard Evaluation.
Health Hazard Evaluation Report 2014-0042-3216 Page i

We evaluated an aircraft engine services 

facility for potential respiratory exposures 

leading to health problems. We learned 

about an incident in July 2013 in which 

overgrowth of sulfate-reducing bacteria 

led to the release of hydrogen sulfide 

gas in the waste water treatment plant. 

From existing records of pulmonologist 

diagnoses, we identified four cases of 

reactive airways dysfunction syndrome, a 

form of irritant-induced asthma, that were 

diagnosed within six months of the incident 

in workers who were in or near the waste 

water treatment plant. We reviewed the 

facility’s incident response and actions with 

the facility management, industrial hygiene 

consultants, and waste water treatment 

plant manager. After learning about the 

incident in July 2013, the facility has taken 

multiple steps to mitigate exposures to 

hydrogen sulfide and prevent similar 

incidents in the future. During informal 

interviews with workers at the facility, we 

learned that at the time of the incident 

there was some confusion about incident 

reporting channels, which contributed 

to a delay in the facility’s response. In 

addition, we learned that some workers 

were concerned about the potential for heat 

stress during the summer months. On the 

basis of these findings, we recommended a 

number of actions focused on engineering 

and administrative controls.

Highlights of this Evaluation

The National Institute for Occupational Safety and Health (NIOSH) received a confidential 

request from employees at an aircraft engine services facility in West Virginia. The 

requestors were concerned about potential air quality issues, proper ventilation on chemical 

electroplating tanks, and cleanliness in the blast room. They felt these exposures, which 

included an incident in July 2013 involving potential exposure to hydrogen sulfide gas, had 

caused respiratory disease and breathing problems.

What NIOSH Did

● We interviewed employee requestors, 

current managers, and the facility’s 

former environmental health and safety 

manager.

● We reviewed documents, including past 

industrial hygiene reports and medical 

records.

● In February 2014, we visited the facility.

● During the visit, we met with company 

management, waste water treatment 

plant operators, consultant industrial 

hygienists, and the facility nurse.

● We conducted private, in-person 

interviews with workers selected from a 

variety of departments.

● We toured the facility and observed 

workers performing their tasks. 

● We sampled the air for hydrogen sulfide 

gas, total and respirable dusts, and 

other gases using real-time monitoring 

and short-term sampling equipment 

throughout the facility.

● We reviewed and discussed with 

management the findings from an 

internal investigation of the July 2013 

incident involving potential exposures to 

hydrogen sulfide gas.

● We reviewed several breathing test 

(spirometry) reports done as part of the 

facility’s medical surveillance program for 

chemists and plate line workers.
Page ii Health Hazard Evaluation Report 2014-0042-3216

● We provided our initial findings and recommendations in a closing meeting and an 

interim letter. 

What NIOSH Found

● Management was cooperative and workers were willing to talk with us. 

● In July 2013, overgrowth of sulfuate-reducing bacteria in a tank in the waste water 

treatment plant led to the release of hydrogen sulfide gas into the air. However, the 

hydrogen sulfide monitors located in the basement of the plant did not alarm.

● Due to poor communication between workers and management (which involved 

confusion about utilizing the company’s Near Miss Cards and/or Incident Reports), the 

problems concerning strong odors and unusual presence of black sludge in the waste 

water treatment plant were not addressed for at least one week. 

● Four workers who worked in or near the waste water treatment plant in July 2013 

developed breathing problems following the incident and were diagnosed by a 

pulmonologist with reactive airways dysfunction syndrome, a form of irritant-induced 

asthma. 

● Facility management performed an internal investigation following the July 2013 

incident and organized a number of corrective and preventive actions. The affected 

workers did not actively participate in the internal investigation. 

● Although the facility uses some electroplating chemicals with respiratory toxicity, 

there are many administrative and engineering controls in place. During the visit, the 

effectiveness of the engineering controls was confirmed with short-term samples taken 

directly over the electroplating tanks, which were all below limits of detection. 

● During the walk through, the blast room was found to be clean and real time sampling 

equipment indicated low particulate levels.

● Safety labeling was clear throughout the facility, and workers we spoke with were aware 

of personal protective equipment and respirator use guidelines. 

● A few workers we spoke with were concerned about the potential for heat stress in the 

electroplating and clean line departments during the summer months. These workers 

asked us about the feasibility of personal cooling fans. 

● The facility has taken steps to address the concerns about heat stress, such as scheduling 

work/rest cycles and providing workers with a variety of drinks (water and electrolyte 

drinks).

● Spirometry was conducted at an offsite clinic and had multiple quality problems. The 

facility’s onsite nurse has attended a NIOSH-approved spirometry course, but the 

facility did not have a functioning spirometer. Following our visit, the facility purchased 

a new spirometer.
Health Hazard Evaluation Report 2014-0042-3216 Page iii

What the Employer Can Do

● Continue to educate workers about the differences between Near Miss Cards and 

Incident Reports. 

● Whenever possible, include the workers involved in an incident in the subsequent 

internal investigation. 

● Before installing or permitting the use of personal fans or cooling devices, perform 

a review of potential cross ventilation effects to ensure ventilation is not adversely 

affected. 

● Work with health and safety committees, supervisors, and workers to increase 

awareness about hydrogen sulfide gas. 

● When evaluating future process changes, including changes to the waste water system, 

consider how they may affect occupational health and safety. Continue to examine all 

scenarios of potential failures in the system, and develop strategies for how these can be 

avoided.

● Continue to routinely monitor for sulfate-reducing bacterial growth in the waste water 

treatment plant.

● Continue to track hydrogen sulfide monitoring results from the real time monitors 

installed in the waste water treatment plant and near the prep room areas.

● Ensure that all spirometry testing conducted on workers is high quality and monitor for 

changes in lung function over time to identify workers with abnormal declines. 

What Workers Can Do

● Report conditions that appear to be unsafe to supervisors, health and safety 

representatives, or the emergency response team right away. 

● Participate in incident investigations if it is possible to do so.

● Check the real time monitors or wear personal sampling badges for hydrogen sulfide gas 

if unusual odors are detected. Inform a supervisor or health and safety representative if 

levels greater than 1 ppm are present. 
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Health Hazard Evaluation Report 2014-0042-3216 Page v

Abbreviations

LOD Limit of Detection

MMF Multi-Media Filter

NIOSH National Institute for Occupational Safety and Health 

NOAA National Oceanic and Atmospheric Administration

OSHA Occupational Safety and Health Administration

PPE Personal Protective Equipment

ppm Parts Per Million

RADs Reactive Airways Dysfunction Syndrome

STEL Short Term Exposure Limit
Health Hazard Evaluation Report 2014-0042-3216 Page 1

Summary

In December 2013, the National Institute for Occupational Safety and Health received a 

confidential health hazard evaluation request from employees of an aircraft engine services 

facility in West Virginia. The requestors were concerned about potential air quality issues, 

proper ventilation on chemical electroplating tanks, cleanliness in the blast room, and 

breathing problems. Five NIOSH investigators (two industrial hygienists, one chemist, one 

physician, and one epidemiologist) visited the facility on February 5 and 12, 2014. During 

these two visits, we met with workers, medical staff, and facility management. In addition, 

we toured the facility and performed real-time and short-term industrial hygiene monitoring. 

The monitoring was performed for screening rather than compliance purposes so that our 

industrial hygienists could better understand typical levels throughout the facility. We also 

reviewed documents provided by the company, including the company’s environmental 

health and safety program manual, results of recent industrial hygiene sampling, injury and 

illness logs, and information about how unsafe conditions are reported. 

We learned about an incident that occurred in July 2013 that involved potential exposure 

to hydrogen sulfide gas, and about the four workers that sought medical attention for 

respiratory illnesses afterward. The incident occurred when overgrowth of sulfate-reducing 

bacteria led to the release of hydrogen sulfide gas in the waste water treatment plant. The 

four workers were diagnosed with Reactive Airways Dysfunction Syndrome (RADs), a form 

of irritant-induced asthma that is associated with one or more exposures to high levels of 

chemical irritant(s). We requested and reviewed the pulmonologist diagnoses records for 

these workers. We reviewed the facility’s incident response and actions with the facility 

management, industrial hygiene consultants, and waste water treatment plant manager. We 

also confirmed the effectiveness of ventilation over the electroplating tanks by sampling the 

air above the tanks.

In conversations with workers, we found that most reported they were comfortable speaking 

to management about health and safety concerns. Several workers were concerned about the 

potential for heat stress during the summer months in the electroplating and clean line areas. 

After the incident occurred in July 2013, the facility management took multiple steps to 

prevent similar incidents from happening. These steps included elimination of a primary 

acidic descaler from the waste water treatment system, addition of an agitator to the main 

media filtration system, scheduling of periodic tests for sulfate-reducing bacteria in the waste 

water treatment plant, installation of additional hydrogen sulfide monitors, and changes to 

the ventilation system. We agreed with these steps and recommended additional worker 

training on hydrogen sulfide gas and incident reporting, as well as inclusion of affected 

workers in future incident investigations. 

 

 
Page 2 Health Hazard Evaluation Report 2014-0042-3216

Introduction

In December 2013, The National Institute for Occupational Safety and Health (NIOSH) 

received a confidential health hazard evaluation request from employees of an aircraft engine 

services facility. The requestors were concerned about potential air quality issues, proper 

ventilation on chemical electroplating tanks, cleanliness of the blast room, and breathing 

problems. During the initial phase of our evaluation, we learned of an incident in July 2013 

that involved potential exposure to hydrogen sulfide gas. On February 5 and 12, 2014, five 

NIOSH investigators visited the facility, met with workers and management, toured the 

facility, and performed real time and short-term industrial hygiene monitoring for screening 

purposes. In March 2014, we sent an interim letter to the company explaining the visit and 

stating recommendations made verbally during the visit. 

Background

The facility is a 200,000 ft2 aircraft engine maintenance, repair, overhaul and assembly facility 

that first opened in 1971. Several engine models are maintained, repaired and overhauled, and 

one model is fully assembled and tested onsite. 

Process Description

Engines in need of repair or maintenance are either shipped to the facility as freight or flown 

to a local hangar and disassembled from the aircraft. They are initially processed in the 

disassembly area of the facility. After disassembly, engines and/or engine parts are evaluated 

in the inspection area. If an engine has external parts that the facility does not handle, these 

parts are removed and returned to the customer. Sometimes, in order to identify breakage 

or abnormalities in engine structure (e.g., metal pitting), the engine part is coated with 

a fluorescent tracer during inspection. Engineers and technicians will then develop an 

individual plan for the repair and overhaul of each engine and engine part.

If needed, the engine parts will first be stripped clean of any oils, grease, carbon build-up, 

grime, or coatings to expose the metal surface. Stripping may be performed physically by 

abrasive blasting and/or chemically by applying alkali solutions or solvents to the part. The 

abrasive blasting materials include aluminum oxide and plastic beads, and the process utilizes 

fully enclosed glove-box blasters. In the clean line area, engine parts may be rinsed, cleaned, 

or deburred with alkaline rust removers and descaling products.

After the engine is stripped and cleaned, it is again inspected, and a repair criterion is 

developed. This means the parts may go to the machine shop (for repairs), welding, 

electroplating, or paint/plasma spray booth areas, as applicable. In the plasma spray booth 

area, a robot is programmed to apply plasma inside a closed booth. The engine parts may also 

be recoated with metals or paints. In the electroplating area, the part is submerged in a tank 

specific to the type of metal or alloy needed for coating.

At the end of the repair process, the engine parts are sent to the build area where they are 
Health Hazard Evaluation Report 2014-0042-3216 Page 3

reassembled and sent to test cells for performance analysis. Finally, engines are packed and 

shipped back to the customer. For engines that undergo overhaul and repair the typical 

turnaround time (back to the customer) is 40-60 days.

During these processes, waste water discharges from the stripping, cleaning, and plating are 

treated onsite at a waste water treatment plant that is located next to the plate line. Separate 

tanks are used to treat cyanide and chromium wastes. Many of the treatment tanks in this area 

are enclosed and ventilated. Some of the tanks, including the main equalization, multi-media 

filter (MMF) feed, flocculation, and pre-ion exchange tanks are not enclosed. The large, open 

equalization tank collects chrome, silver, and other metal wastes after they undergo individual 

pre-treatment. Typically, the organic acid descaling products that are used for engine 

cleaning are also treated and added to the main equalization tank. Afterward, this solution 

is sent to another series of treatment tanks, where the solution is balanced (using sodium 

metabisulfite and/or sulfuric acid, depending on the pH). During pre-treatment, all of the 

metals from electroplating processes are precipitated out in solution and a polymer is added 

to settle out aggregate waste materials. This polymer residue is then discarded as hazardous 

waste. Finally, the mixture is pressed and the remaining water is flushed through a complex 

MMF system. In the final treatment tank, sodium hydroxide may be added to rebalance the 

pH before final discharge from the facility. The waste water treatment process is operated by a 

contracted environmental services company.

Emergency Response and Incident Investigation 

Some hourly employees are assigned to be members of an Emergency Response Team (ERT). 

This team responds to incidents requiring immediate attention that have been properly 

reported. The company’s definition of such an “incident” can include both near misses (if 

serious), and actual events like detection of strange odors. In 2013, there were approximately 

12 incident investigations at the facility. 

Following the incident in July 2013, a team of worker representatives and management 

performed an incident investigation and organized a number of corrective and preventive 

actions. The affected workers did not actively participate in the internal investigation. The 

steps in the investigation were to 1) define the incident and establish the sequence of events; 

2) investigate the cause or reason; 3) verify what happened; and 4) insure that a similar 

incident does not happen again. 

Some important actions following the July 2013 internal investigation included the 

elimination of a primary acidic descaler from the waste water treatment system, the addition 

of an agitator to the main media filtration system to prevent stagnant conditions which 

support bacterial growth, scheduling of periodic tests for sulfate-reducing bacteria in 

the waste water treatment plant, the installation of additional hydrogen sulfide monitors 

(in the electroplating area and prep room where workers spend a large amount of their 

time), provision of real time personal hydrogen sulfide monitors for plate line workers to 

voluntarily monitor their own exposures, reduction of the warning and alarm signal levels on 

the hydrogen sulfide monitors (to 1 and 5 ppm, respectively), and re-routing the ventilation 
Page 4 Health Hazard Evaluation Report 2014-0042-3216

system so that make-up air in the electroplating prep room is supplied from the machine shop 

area instead of the waste water treatment plant and electroplating line area. 

Personal Protective Equipment and Respiratory Protection Program

Required personal protective equipment (PPE) in receiving and machine shop areas may 

include safety glasses, steel toe shoes, and gloves. During tank additions in the electroplating 

areas, workers typically wear gloves, face shield, apron, and protective sleeves if needed. 

Additional PPE and respiratory protection may be required in the paint and plasma rooms, 

including a supplied air respirator, Tyvek or heat-resistant suits, and protective chemical 

gloves during sprays and applications. 

Respiratory protection consists of disposable filtering facepiece respirators, full facepiece 

respirators with cartridges, and tight-fitting full facepiece masks used with a self-contained 

breathing apparatus or supplied air. At the facility, the workers involved with handling 

cadmium compounds are enrolled in the cadmium-related Occupational Safety and Health 

Administration (OSHA) Medical Surveillance Program (29 CFR 1910.1027). Spirometry is 

conducted routinely at an off-site clinic for the workers enrolled in this program.

Methods

Prior to Site Visit

Prior to our visit to the facility, we interviewed the requestors to better understand their 

health concerns, safety practices, and potential exposures at the facility. We also had two 

telephone conversations with facility management from environmental health and safety and 

human resources departments. 

In addition, we contacted the regional OSHA office in Charleston, WV to learn more about 

a complaint that was filed concerning an incident on July 16 and 17, 2013 that involved 

potential exposure to hydrogen sulfide gas in the waste water treatment plant. We learned 

that the waste water treatment area was located in the same building and next to the 

plating and clean line areas. At the time of the incident, the waste water treatment plant 

was being operated by a contracted environmental services company. We learned from the 

complaint that four workers had experienced sore throat, mucus, cough, irritated eyes, chest 

congestion, and nausea during the incident. One worker reported having ulcers in his mouth 

following the incident. We learned that some workers were still seeing an occupational 

health physician for persisting respiratory symptoms, six months after the incident. We also 

learned from OSHA that some current workers were requesting facility Safety Data Sheets 

for chemicals potentially involved in the July incident to provide more information to their 

occupational physicians. 

After our telephone conversation with management, the facility personnel provided us with 

requested documentation in a timely manner. This included: a labeled map of the facility, 

internal and external industrial hygiene reports from the last two years, OSHA 300 logs of 

recordable illness and injury during the past 5 years, a copy of the respiratory protection 
Health Hazard Evaluation Report 2014-0042-3216 Page 5

program, an environmental health and safety handbook, and the company’s environmental, 

health and safety program manual. We also reviewed existing medical and industrial hygiene 

literature about known health effects from exposure to hydrogen sulfide gas, as well as the 

potential for accidental sulfide gas releases during waste water treatment processes. We 

contacted the four workers who had experienced healthy symptoms following the incident to 

request and review medical records. We obtained the records from a pulmonologist. 

Site Visit 

Upon arrival at the site on February 5, 2014, we had an opening meeting, which was attended 

by local and corporate management, consultant industrial hygienists, the onsite nurse, a 

worker representative, supervisors from around the facility (including maintenance and 

engineering), and a representative from the human resources department, to discuss the 

nature and itinerary for our site visit. During this meeting, we learned about the facility’s 

history of manufacturing and engine repair processes.

We toured the facility to improve our understanding of the facility processes. At our request, 

the facility’s Environmental Health and Safety coordinator took photographs be taken of 

equipment, tanks, and safety labeling. We learned more about specific requirements for PPE 

and training in different areas throughout the facility. 

Following the tour, our two industrial hygienists and chemist returned to explore the facility 

in more depth. We revisited some areas (e.g. blast room, machine shop, electroplating and 

clean lines, waste water treatment plant) to observe workers performing tasks. We performed 

real-time and short-term industrial hygiene monitoring for screening rather than compliance 

purposes, so that we could better understand typical levels of carbon monoxide, hydrogen 

chloride, nitrous gases, hydrogen sulfide, sulfur dioxide, volatile organic compounds, and 

total and respirable dust throughout the facility. Additionally, we wore two types of real time 

monitoring equipment on our persons and brought a number of direct reading, colorimetric 

tubes for air sampling. These devices measure an array of different particles and gases, as 

described in Table 1. We took samples from both general work areas and directly over 

plating tanks and waste water tanks. We also spoke with the industrial hygiene consultant 

about the facility’s ongoing industrial hygiene monitoring strategy, as well as how the 

monitoring strategy was adjusted following the July 2013 incident. 

Our physician and epidemiologist informally interviewed workers from all over the facility. 

These confidential interviews were intended to provide us with a better understanding of 

individual safety practices and PPE use, and to identify any health and safety concerns that 

might exist in the workforce. We also talked to workers about the July 2013 incident, if they 

were present at the time. We provided copies of an informational handout regarding the 

NIOSH visit, and offered pamphlets on the NIOSH health hazard evaluation program [CDC 

2009]. Lastly, we reviewed medical records (e.g., spirometry test reports) and spoke with 

the facility nurse about health and safety issues and medical surveillance procedures and 

capabilities. 
Page 6 Health Hazard Evaluation Report 2014-0042-3216

At the end of first day, we scheduled a second visit for February 12, 2014 in order to 

accommodate the participation of the contracted waste water treatment facilities manager 

who was unable to make the initial meeting. 

During the second visit on February 12, 2014, our physician and epidemiologist interviewed 

more workers and collected additional spirometry test reports for review. Our industrial 

hygienists and chemist met with the facility management, the worker representative, and 

the contracted waste water treatment facilities manager, to specifically review the root 

cause of the July 2013 incident and the company’s investigation and response. At this time, 

management provided us with a report documenting the company’s investigation. The waste 

water treatment plant manager provided us with information on the semi-quantitative test 

for visual determination of sulfate-reducing bacteria (visual determination, SRB-BARTTM) 

and sulfates in water solutions or produced waters (USEPA Method 8051). At the end of the 

visit, we requested a picture documenting the visual test and a full description of a hydrogen 

sulfide verification test performed in the waste water treatment plant following the incident. 

These were provided to us on February 25, 2014. 

At the end of the second visit, we held a closing meeting to discuss our preliminary 

recommendations and the future course of the evaluation. 

After the Site Visit

We prepared an interim letter summarizing our findings and initial recommendations. This 

was sent to the company, confidential requestors, OSHA, and the state health department in 

March 2014. 

Results

Incident Description

On July 9 2013, some workers filed Near Miss Cards referencing strong and unusual “rotten 

egg-like” odors in the electroplating and waste water treatment work areas. At this time, some 

workers began experiencing respiratory irritation, headache, and nausea associated with the 

strong odors. An atypical “black sludge” floating in some of the waste water treatment plant 

tanks was noted at this time. During the time period of July 9-16, high outdoor temperatures 

ranged from 82-95 °F (28-35°C) [NOAA, 2013], although temperatures may have been higher 

indoors near the electroplating tank lines, as these lines involve hot processes. Seven days 

passed until, on July 16, 2013, one of the electroplating line workers directly contacted the 

environmental health and safety coordinator and again reported strong, unusual odors and 

some health symptoms that included scratchy/sore throat, cough, and phlegm. Workers 

in the area reported losing the ability to smell the odor over the course of the day. After 

management learned about the situation, the five workers who were experiencing symptoms 

were relieved from work duties in the electroplating line on the same day. Five days later, 

these workers returned and were stationed in other work locations of the facility. This 

included four electroplating line technicians and one maintenance technician. In the waste 
Health Hazard Evaluation Report 2014-0042-3216 Page 7

water treatment plant, the hydrogen sulfide monitoring device located in the basement that 

had a warning signal at 5 ppm and an alarm signal at 10 ppm did not activate. Although 

the basement was open to the wastewater and electroplating areas, the hydrogen sulfide 

monitoring device was not in the same location as where the electroplating workers were 

regularly performing job tasks.

The waste water treatment plant manager explained that the specific incident had not been 

anticipated because hydrogen sulfide gas releases were not a common phenomenon in 

treatment plants dealing with such low levels of organic compounds. We confirmed both 

with company management and workers that the unusual odors and sludge build-up began 

when a specific organic acidic descaling product (which is used to remove metallic heat 

scales from jet engines) began to be treated regularly in the plant. In addition, the new MMF 

system had been recently installed, and the sludge first became visible at the bottom of the 

MMF feed tank. At the time, this tank was not being agitated, allowing the water to become 

stagnant. 

Document Review

Our review of both the OSHA 300 logs and medical records revealed that four workers were 

diagnosed with Reactive Airways Dysfunction Syndrome (RADS) following the July 2013 

incident. Respiratory symptoms including shortness of breath, cough, and wheeze persisted 

for months despite cessation of exposure and use of breathing medications. Three of the four 

workers received temporary worker’s compensation for the RADS diagnosis. The OSHA 

log also described four workers in the electroplating and repair areas who had experienced 

respiratory and gastrointestinal symptoms stemming from a potential exposure to a freshly 

applied floor coating in May 2010. After examining the safety data sheet for the floor coating 

product, we learned that the gloss was a polyester resin that contained small amounts of 

xylene, ethyl-benzene, and dibutyltin dilaurate. One of the workers diagnosed with RADS in 

2013 was involved in both chemical exposure incidents. 

The facility contracts with industrial hygiene consultants to perform an array of routine air 

monitoring. We reviewed all industrial hygiene reports of monitoring done at the facility 

from years 2011 to 2013. In the electroplating and clean line areas, sampling included 

monitoring for hexavalent chromium, hydrogen cyanide, and ethanolamine to ensure that 

ventilation and capture systems are performing. Other industrial hygiene sampling included 

monitoring for airborne metal exposures (e.g., aluminum, molybdenum, and nickel) in the 

plasma area, welding fumes in the welding shop, and volatile organic compounds in the paint 

shop. 

Following the July 2013 incident, the facility management requested that the consultants 

perform real time air monitoring for hydrogen sulfide gas at various locations throughout 

the facility, including the electroplating and clean line areas, as well as in the waste water 

treatment plant. The facility also collected a large amount of real time data with a MultiRAE 

Photoionization Gas Detector (RAE Systems, San Jose, CA) inside the prep room from July 

23 to November 20, 2013. Overall, hydrogen gas levels were low, ranging from below the 
Page 8 Health Hazard Evaluation Report 2014-0042-3216

Limit of Detection (LOD) to 0.3 ppm. On July 24-31, 2013 the monitor reported some levels 

of 0.1 to 0.2 ppm. The industrial hygiene consultants noted that these levels decreased after 

the facility cleaned the MMF tanks. 

Industrial Hygiene Screening Results During Site Visit

We did not notice any unusual odors during the site visit. Table 1 provides a description of 

industrial hygiene monitoring that was conducted on February 5, 2014 during the facility 

visit. All of the chemical and dust sampling results collected using real-time instruments 

were below applicable occupational exposure limits. Real time monitoring for total and 

respirable dust with a Dustrak DRX Aerosol Monitor (Model 8534) indicated total dust levels 

less than 1 mg/m3 and respirable dust levels less than 0.4 mg/m3

 throughout areas including 

the electroplating line, clean line, blast room, machine shop, shipping/receiving, and office 

areas. When real time monitoring for total and respirable dust was performed in the blast 

room, a worker was operating a fully enclosed glove-box blaster. The short-term sampling 

results collected for carbon monoxide, hydrogen chloride, nitrous gases, hydrogen sulfide, 

and sulfur dioxide were below the LOD. In addition, our industrial hygienists observed that 

visible mist from the electroplating tanks was being pulled away from the breathing zone into 

local exhaust directly above the tank. We also learned that some of the electroplating tanks 

without similar local exhaust systems (e.g., nickel tanks) had an added surfactant to help 

prevent the release of mists. 

Worker Interviews

Everyone at the facility was friendly, welcoming, and generally willing to discuss jobs and 

processes, their personal sense of overall health and safety, and the July 2013 incident with 

us. We informally interviewed 11 workers from the repair line, machine shop, maintenance, 

electroplating line, clean line, paint shop, assembly line, and plasma departments. The 

tenure for these workers ranged from 1 to 28 years. Most workers felt safe at work and did 

not report many symptoms that they attributed to the workplace. Many informed us that 

they were comfortable notifying and speaking with supervisors if they had a health and 

safety concern. Two workers were concerned about the potential for heat stress during the 

summer months in the electroplating and clean line areas. We learned that there is no airconditioning in these areas due to high ventilation rates of processes. The workers informed 

us that since some processes are heated, during the summer these areas of the facility can 

reach near or above 100°F (38°C). 

Although a few of these workers were present at the facility during the July 2013 event, 

they informed us that they currently felt safe working at the facility. One worker told us 

that he frequently checks the readings on the new hydrogen sulfide monitors and has not 

seen elevated levels in the time since the event occurred. A few workers had noticed some 

reoccurring rotten egg smells in the past, but they reported that it was not bothersome 

and did not cause symptoms. Another worker informed us that when a smell is detected, 

he checks the hydrogen sulfide monitors and sometimes chooses to put on one of the 

personal monitors that are available to electroplating and clean line workers in the plate line 

room. 
Health Hazard Evaluation Report 2014-0042-3216 Page 9

On-site interviews with health professionals

The facility contracts with a local clinic to have a nurse onsite full-time. The nurse oversees 

medical surveillance, including hearing conservation for about 120 workers and annual 

medical evaluations including spirometry for less than a dozen chemists and electroplating 

line technicians, as per the OSHA standards for cadmium and chromium. The facility’s 

nurse took a NIOSH-approved spirometry course and was conducting spirometry onsite 

until about a year prior to our visit. At that time, the spirometer she was using stopped 

functioning, and she began sending workers to an off-site clinic for spirometry.

Our review of reports of spirometry tests done at the off-site clinic revealed multiple 

quality issues. These issues included outdated reference equations, outdated interpretation 

algorithms, and technical errors that could lead to inaccurate estimations of lung function. 

After our first visit, we reported these issues to the facility nurse, who obtained permission 

from plant management to purchase a new spirometer for use at the plant. We later provided 

feedback on the spirometer settings and reviewed a report prepared using the new device. 

The testing met recommended quality criteria. 

Incident Response

The facility took several corrective actions after the incident was reported to the 

environmental health and safety coordinator. The addition of sulfuric acid into the ion 

tanks was immediately halted and all scrubbers were rinsed with clean water. The contracted 

waste water treatment facilities manager arrived that evening to collect waste water from 

a few different tanks for sulfide testing. Eventually, the bacterial source of the hydrogen 

sulfide off-gassing was identified at the MMF feeding tank. This was confirmed with a semiquantitative test for visual determination (white precipitate) of sulfate-reducing bacteria 

(visual determination, SRB-BARTTM) and sulfates in water solutions or produced waters 

(USEPA Method 8051). The organic acid descaler product was no longer added to the waste 

water system. Instead, it was collected, packaged, and disposed of as hazardous waste offsite.

Within 1 month of the incident, the facility made additional changes. The MMF tanks were 

completely drained, cleaned, and all filters were replaced. An agitating device was added to 

the MMF feed tank to ensure that sludge would not accumulate in stagnant water conditions. 

In addition, the facility installed new ductwork to pull in a mix of outdoor air and machine 

shop air instead of recirculating air in the waste water treatment plant and electroplating area. 

Also within 1 month of the incident, all plate line workers were provided with GX-2009 RKI 

Four Gas Confined Spaces Monitor (Union City, CA) personal monitors for continuous 

hydrogen sulfide monitoring. The workers were trained on how to use the personal monitors 

to voluntarily monitor their own exposures. These monitors were stored in the prep room. 

Within 6 months, the contracted industrial hygiene team performed air monitoring and 

conducted air flow studies to determine the placement of two additional real time hydrogen 

sulfide monitors. After installing the monitors, the facility began to conduct more frequent 

calibration of the monitor sensors. The sensors were set to lower warning and alarm signals, 

at 1 ppm and 5 ppm, respectively. The facility required that an onsite sulfates analysis be 
Page 10 Health Hazard Evaluation Report 2014-0042-3216

performed once per shift to check on potential bacteria growth to prevent incidents in the 

future.

 Finally, the facility revised its system for reporting incidents, and has begun to train workers 

about the differences between Near Miss Cards and Incident Reports. Currently, there are 

future plans to construct a wall entirely separating and enclosing the waste water treatment 

plant from the electroplating and clean lines. The RKI Four Gas Confined Space personal 

monitors for continuous hydrogen sulfide monitoring have been replaced with the newer 

GX-2012 model. 

Field Observations

During our visit, we observed that the facility was clean. Specific locations and department 

areas were labeled. At the entrance of many specific areas of the facility, there were clearly 

labeled health and safety guidelines, specifying the types of PPE, surveillance, and training 

that was required prior to entering the area. Many typically-hazardous processes, like 

abrasive blasting, painting, and plasma application were enclosed or automated. There were 

many ventilated areas throughout the facility. In the electroplating and clean line areas, 

there were local and general exhaust systems operating to pull electroplating mists or fumes 

away from the worker’s breathing zone. The local exhaust consisted of nearby slots over the 

electroplating tanks pulling evaporation at the source. Some surfactants were also used in 

tanks to prevent misting. We confirmed that exposures were low over these plating and clean 

line areas by taking some short-term Drager tube samples in the electroplating and clean 

line aisles, as well as directly over some of the electroplating and clean line tanks (see results, 

Table 1). 

In the electroplating department, we informally spoke with workers and learned that 

approximately 80% of their time during the work shift is spent in the prep room, and that 

many workers from the clean line department also enter this room for periodic breaks. 

We learned that during the incident, this room was receiving make-up air through the airconditioning unit from the electroplating and waste water treatment areas. After a brief 

discussion with the facility’s industrial hygiene consultant, we learned that some air flow 

studies were conducted after the incident, and these studies revealed that the general air flow 

direction was from the waste water treatment plant to the electroplating line. Since the July 

2013 incident, the facility has installed new ductwork to pull make-up air from the machine 

shop area through the air conditioning unit instead of recirculating the air from the waste 

water treatment plant and electroplating line areas. 

In the waste water treatment plant, many of the tanks (e.g., chromium, cadmium) were 

enclosed. However, some of the tanks were open, which may be necessary for proper 

chemical and physical reactions during the treatment process.

 
Health Hazard Evaluation Report 2014-0042-3216 Page 11

Discussion

Industrial Hygiene Monitoring

Hydrogen sulfide exposures are often associated with municipal sewers, sewage treatment 

plants, and oil drilling operations, which are characterized by high levels of organic materials. 

This is because bacteria and fungi can release hydrogen sulfide during the decomposition 

of sulfur-containing proteins and by the direct reduction of sulfate. OSHA has established 

an acceptable ceiling concentration of 20 ppm for hydrogen sulfide in the workplace, 

with a short term exposure limit (STEL) of 50 ppm over a 10 minute duration if no other 

measurable exposure occurs during the 8-hour work shift. NIOSH has set a Recommended 

Exposure Limit 10-minute ceiling value of 10 ppm. The ACGIH recommended exposure 

limits are much lower, with a time weighed average of 1 ppm over the course of an 8 hour 

work shift, and a STEL of 5 ppm over 15 minutes. 

We took air samples during the walk through visit in February 2014 to determine if there 

were current exposures to hydrogen sulfide, sulfur dioxide, nitrous gases, hydrogen cyanide, 

volatile organic compounds, carbon monoxide, and total and respirable dust. We did not 

detect current exposures at the facility at concerning levels, and most of the air monitoring 

samples were below instrument detection limits. It should be noted that the measurements 

taken by our industrial hygiene team occurred several months after the time of the incident, 

after clean-up had occurred and the sulfate-reducing bacteria had been cleared. Although 

the hydrogen sulfide monitors in the waste water treatment basement area did not alarm 

during the July 2013 incident, it is unknown if the monitor was measuring the same levels 

experienced in the mezzanine above, which included the electroplating line, clean line, and 

prep room. The industrial hygiene reports generated by external consultants (which began 

within one week of the incident) also demonstrated low levels, which were all ≤ 0.3 ppm. 

Since hydrogen sulfide has such a low odor threshold, it is possible that slight odors may 

have still been detected by workers even after the incident occurred, despite documented 

levels in the prep room ≤0.3 ppm. In addition, some of the levels measured (0.1-0.3 ppm) in 

these reports could have been due to instrument calibration issues with the Photoionization 

Detector. After the facility re-calibrated the instrument on September 3, 2013, most of the 

gas levels were all below the LOD. 

Health Effects

Exposure to hydrogen sulfide can result in a wide range of short-term health effects, from 

mucous membrane irritation to loss of consciousness, respiratory paralysis, and death. 

Health effects vary with the concentration of hydrogen sulfide in the air. At 50 ppm, eye, 

nose, and throat irritation occur [Reiffenstein et al. 1992; Knight and Presnell 2005; ATSDR 

2006]. At 250-300 ppm, pulmonary edema, in which the lungs fill with fluid, occurs. At 500 

ppm and higher, loss of consciousness, respiratory paralysis, cardiac arrhythmias and death 

result. Other possible effects of hydrogen sulfide exposure include headache and nausea. 

Some individuals may be more sensitive to hydrogen sulfide exposure. In one study, people 

with asthma who were exposed to low concentrations of hydrogen sulfide (2 ppm) for 30 
Page 12 Health Hazard Evaluation Report 2014-0042-3216

minutes suffered impairment in lung function with the exposure [Jappinen et al. 1990]. 

Long-term health effects of hydrogen sulfide exposure also have been described and 

respiratory health effects are notable. Shortness of breath was the complaint of 23% of 

workers in Alberta, Canada seeking compensation after hydrogen sulfide exposure [Arnold 

et al., 1985]. Among oil and gas workers, those who had experienced loss of consciousness 

from hydrogen sulfide exposure were more likely to later report shortness of breath, wheeze 

with chest tightness, and attacks of wheeze [Hessel et al. 1997]. A study of sewer workers 

found lower lung function related to hydrogen sulfide exposure [Richardson 1995]. These 

symptoms and abnormalities are consistent with airways diseases including asthma and/or 

scarring of the small airways. In addition, pulmonary fibrosis, a scarring lung disease, has 

also been described after hydrogen sulfide exposure [Parra 1991; Duong et al. 2001].

In addition, long-term neurological problems have been reported after hydrogen sulfide 

exposure. These include persistent headaches, lack of concentration, poor attention span, 

impaired short-term memory, and impaired motor function [ATSDR 2006 Doujaiji et al. 

2010; Nam et al. 2004]. 

The odor threshold for hydrogen sulfide ranges from 0.0005 to 0.3 ppm [Reiffenstein et al. 

1992; Knight and Presnell 2005; ATSDR 2006]. At 10 ppm, an unpleasant odor is obvious 

and at 30 ppm, the odor is described as strong or intense. At higher concentrations (100-150 

ppm), sense of smell is impaired. Therefore, it is important not to rely on smell to determine 

if an exposure has ended. The disappearance of a hydrogen sulfide odor could mean that the 

concentration is high enough to cause loss of the sense of smell. 

During the July 2013 incident, workers reported a sulfurous odor and associated symptoms 

(e.g., scratchy/sore throat, cough, phlegm, headache, and nausea). Olfactory fatigue 

(loss of sense of smell) was also noted. These observations suggest that hydrogen sulfide 

concentrations may have been as high as 100 ppm. However, without proper monitoring 

data, we are unable to verify that such levels were present. 

Following the incident, four workers had persistent respiratory symptoms, consistent 

with previous reports of long-term respiratory impairment following hydrogen sulfide 

exposure. These workers were diagnosed with RADS, a form of irritant-induced asthma that 

is associated with one or more exposures to high levels of chemical irritant(s) [Tarlo and 

Lemiere 2014]. Once RADS develops, symptoms such as cough and shortness of breath can 

persist for years. In one study of 35 workers who developed RADS after exposure to chlorine 

gas or other agents, all still had asthma symptoms and two-thirds were still using inhalers 

four or more years after the exposure [Malo et al. 2009]. 

Workers who perform the majority of their work in hot environments may be at risk for heat 

stress. Exposure to extreme heat can result in occupational illnesses and injuries. Heat stress 

can result in heat stroke, heat exhaustion, heat cramps, or heat rashes. After our visit, we are 

aware the facility is looking into many potential ways to solve this issue. The company does 

have some programs in place to prevent heat stress. Overall, the workers that we interviewed 
Health Hazard Evaluation Report 2014-0042-3216 Page 13

were aware of work/rest cycles and they informed us that they take breaks in the Prep Room, 

which is air conditioned. A supply of electrolyte beverages and water is provided by the 

facility for workers.

We learned that the facility management responded quickly to the incident upon learning 

about the problem on July 16, 2013. However, we also learned from some of the workers that 

the smells and dark sludge were detected a week earlier. It is likely that poor communication 

between workers and management contributed to the delayed response. At the closing 

meeting, we discussed the importance for workers to be trained on and understand the 

proper communication channels for reporting incidents like the one that occurred in July 

2013. 

Conclusions

We evaluated an aircraft engine services facility for potential respiratory exposures leading 

to health problems. We learned about an incident in July 2013 that involved overgrowth 

of sulfate-reducing bacteria that led to the release of hydrogen sulfide gas in the waste 

water treatment plant, and reviewed the incident response and actions taken by facility 

management, industrial hygiene consultants, and the contracted environmental services 

company. We identified four cases of RADS that had been diagnosed by a pulmonologist 

in workers within six months of the incident who were in or near the waste water treatment 

plant. In order to determine if there were any current exposures to hydrogen sulfide, we 

measured for airborne sulfur dioxide and hydrogen sulfide gas. We also sampled for nitrous 

gases, hydrogen cyanide, volatile organic compounds, carbon monoxide, and total and 

respirable dust during a visit to the facility on February 5, 2014. We did not detect current 

exposures at the facility at concerning levels and most of the samples were below instrument 

detection limits. During informal interviews with workers at the facility, we learned that at 

the time of the incident there had been some confusion among reporting channels for Near 

Miss Cards and Incident Reports, and that approximately one week had passed between 

when sulfur-containing odors were initially filed on a Near Miss card to when the workers 

formally informed a supervisor. 

We also learned during our interviews with workers at the plant that some were concerned 

about the potential for heat stress during the summer months. On the basis of these findings, 

we recommended a number of actions focused on primarily engineering and administrative 

controls.

Recommendations

On the basis of our findings, we recommend the actions listed below. These recommendations 

are based on an approach known as the hierarchy of controls. 
Page 14 Health Hazard Evaluation Report 2014-0042-3216

Elimination and Substitution 

Eliminating or substituting hazardous processes or materials reduces hazards and protects 

workers more effectively than other approaches. Prevention through design, considering 

elimination or substitution when designing or developing a project, reduces the need for 

additional controls in the future.

1. Continue to treat the descaling product as a potential hazardous waste and have the 

product treated off site. 

2. Work with the waste water treatment plant manager to continue assessing the potential 

for similar incidents for other jet engine cleaners and descaling products by flagging 

new products that have similar acidic components and chemical properties. 

Engineering Controls 

Engineering controls reduce worker’s exposures by removing the hazard from the process 

or by placing a barrier between the hazard and the employee. Engineering controls protect 

workers effectively without placing primary responsibility of implementation on the 

employee. 

1. Prior to installing any personal cooling fans to address heat stress concerns, investigate 

the potential effects of fan operation on important ventilation systems in the 

electroplating and clean lines.

Administrative Controls 

The term administrative controls refers to employer-dictated work practices and policies 

to reduce or prevent hazardous exposures. Their effectiveness depends on employer 

commitment and employee acceptance. Regular monitoring and reinforcement are necessary 

to ensure that policies and procedures are followed consistently.

1. Continue communication with potentially affected workers after an incident and 

involve them in the incident investigation if possible. 

2. Consider potential occupational health and safety impacts of process changes, such as 

installation of the MMF filters. Continue to examine and prepare for scenarios in case 

of system failure and develop strategies for how these can be avoided in advance.

3. Continue to periodically perform industrial hygiene monitoring for hydrogen sulfide, 

sulfur dioxide, and sulfuric acid on workers who perform work in areas were sulfuric 

acid and inorganic sulfides are used. If workers are wearing the GX-2012 RKI Four 

Gas Confined Space personal monitors for continuous hydrogen sulfide monitoring, 

develop a plan to track their monitoring results. This also allows facility management 
Health Hazard Evaluation Report 2014-0042-3216 Page 15

to gain insight about who wears the monitors, and how often. This includes workers 

who are employed by the contracted environmental services company that operates the 

waste water treatment plant. 

4. Continue to use the warning signal at 1 ppm (ACGIH TWA for hydrogen sulfide 

during an 8-hour work shift) and the alarm signal of 5 ppm (ACGIH STEL for 

hydrogen sulfide) on all area monitors. 

5. Educate workers about the nature of hydrogen sulfide exposures during employee 

health and safety training. Some training topics may include: Information on how 

the gas is generated biologically and how the odor detection level differs from 

recommended exposure limits.

a. Prevention of conditions for bacterial growth.

b. Locations and instructions for reading the current hydrogen sulfide monitors (e.g., 

monitor limits of detection, alarms, frequency of sensor calibration).

c. How to wear and operate personal sampling devices if odors are detected. 

d. Types of health effects (signs and symptoms) that are associated with different 

levels of hydrogen sulfide exposures. Discuss how the detection via smell may 

differ from the concentration at which health effects are initially observed. 

6. Continue to train workers on how to readily differentiate a Near Miss from an accident 

or incident requiring immediate notification to a supervisor or the Emergency 

Response Team. 

7. Spirometry should be conducted onsite by the facility nurse, as she has taken a NIOSHapproved course in spirometry; this change is now underway. We also provided 

information about SPIROLA, a software program that can be used to track lung 

function over time. SPIROLA is available free on the NIOSH website (http://www.cdc.

gov/niosh/topics/spirometry/spirola-software.html). 

8. Continue to educate workers about work/rest cycles, hydration, and cooling centers 

during summer months. 

 
Page 16 Health Hazard Evaluation Report 2014-0042-3216

References

ACGIH [2013]. 2013 TLVs® and BEIs®: threshold limit values for chemical substances and 

physical agents and biological exposure indices. Cincinnati, OH: American Conference of 

Governmental Industrial Hygienists.

Arnold IM, Dufresne RM, Alleyne BC, Stuart PJ [1985]. Health implication of occupational 

exposures to hydrogen sulfide. J Occup Med 27:373-376. 

ATSDR [2006]. Toxicological profile for hydrogen sulfide. US Department of Health and 

Human Services, Agency for Toxic Substances and Disease Registry. Atlanta, GA.

Burnett WW, King EG, Grace M, Hall WF [1977]. Hydrogen sulfide poisoning: Review of 5 

years’ experience. Can Med Assoc J 117:1277-1280.

Doujaiji B and JA Al-Tawfiq [2010]. Hydrogen sulfide exposure in an adult male. Ann Saudi 

Med. 30:76.

Duong TX, Suruda AJ, Mair LA [2001]. Interstitial fibrosis following hydrogen sulfide 

exposure. Am J Ind Med 40:221-224.

Hessel PA, Herbert FA, Melenka LS, Yoshida K, Nakaza M [1997]. Lung health in relation to 

hydrogen sulfide exposure in oil and gas workers in Alberta, Canada. Am J Ind Med 31:554-

557.

Jappinen P, Vilkka V, Marttila O, Haahtel T [1990]. Exposure to hydrogen sulphide and 

respiratory function. Br J Ind Med 47:824-828.

Knight LD and Presnell SE [2005]. Death by sewer gas: case report of a double fatality and 

review of the literature. Am J Forensic Med Pathol 26:181-185.

Nam B, Kim H, Choi Y, Lee H, Hong ES, Park JK, Lee KM, Kim Y [2004]. Neurologic sequela 

of hydrogen sulfide poisoning. Ind Health, 42: 83-87.

NIOSH [2009]. Health hazard evaluation program. Cincinnati, OH: US Department of 

Health and Human Services, Centers for Disease Control and Prevention, National Institute 

for Occupational Safety and Health. DHHS (NIOSH) Publication No. 2009-167. http://www.

cdc.gov/niosh/docs/2009-167/. Accessed February, 2014.

NIOSH [2010]. NIOSH pocket guide to chemical hazards. Cincinnati, OH: U.S. Department 

of Health and Human Services, Centers for Disease Control and Prevention, National 

Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2010-168c. 

http://www.cdc.gov/niosh/npg/.Accessed: February, 2014 
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NIOSH [2013]. “Spirometry longitudinal data analysis (Spirola) software.” US Department of 

Health and Human Services, Centers for Disease Control and Prevention, National Institute 

for Occupational Safety and Health. http://www.cdc.gov/niosh/topics/spirometry/spirolasoftware.html. Accessed February, 2014.

NOAA. Record of Climatological Observations, Bridgeport, WV. North Central WV 

Airport. http://www.ncdc.noaa.gov/cdo-web/datasets. Accessed February, 2014.

OSHA. Cadmium Compliance Program. 29 CFR 1910.1027. 

Parra O, Monso E, Gallego M, Morera J [1991]. Inhalation of hydrogen sulphide: a case of 

subacute manifestations and long term sequelae. Br J Ind Med 48: 286-287.

Reiffenstein RJ [1992]. Toxicology of hydrogen sulfide. Ann Rev Pharmacol Toxicol pp. 109-

34.

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Med 28:99-108.
Page 18 Health Hazard Evaluation Report 2014-0042-3216 Table Table 1: A description of industrial hygiene monitoring that was conducted during the plant visit, February 5, 2014. Particles/Gases Type Monitoring Equipment Sample Time Period N Samples LOD Result (Range) NIOSH REL (or OSHA PEL) Locations Monitored Hydrogen Sulfide (H2S) 5 0.2 ppm All samples <LOD 10 ppm [10-minute] Electroplating line, clean line, waste water treatment plant. Sulfur Dioxide (SO2) 1 1 ppm All samples <LOD TWA 2 ppm Waste water treatment plant. Nitrous Gases (NOX) Draeger Tubes Short Term (1-5 minutes) 4 2 ppm All samples <LOD TWA 25 ppm (Nitric Oxide) Electroplating line, clean line, waste water treatment plant. Hydrogen Cyanide Gases (HCN) 1 2 ppm All samples <LOD ST 4.7 ppm Electroplating line. H2S 2* 1 ppm All samples <LOD 10 ppm [10-minute] All throughout the plant (electroplating line, clean line, blasting room, machine shop, shipping/receiving, office areas). The sampling wand was extended directly over electroplating tanks and hung from the mezzanine directly into open waste water treatment tanks. Volatile Organic Compounds (VOCs) MultiRAE Plus, with sampling wand (extended coil tubing). Real Time Sampling (15 second intervals) 2* 0.1 ppm <LOD-0.5 ppm NA, varies by compound Carbon Monoxide (CO) 2* 0.1 ppm <LOD-0.2 ppm TWA 35 ppm Total Dust Dustrak DRX Aerosol Monitor Real Time Sampling 2* 0.001mg/ m3 0.001 – 0.939 mg/ m3 15 mg/m3† All throughout the plant (electroplating line, clean line, blasting room, machine shop, shipping/receiving, office areas). Respirable Dust Model 8534 Handheld (15 second intervals) 0.001mg/ m3 0.001 – 0.334 mg/ m3 5 mg/m3†

TWA = Time Weighted Average; ST = Short Term; *These samples were real time monitoring equipment continuously measuring over 15 second intervals. These devices were 

taken in to the plant on two occasions. The first sampling occurred during the initial walk through tour and the second sample occurred during the industrial hygienist’s return visit (both sampling periods were ~11⁄2 hours). †There is no NIOSH REL for total and respirable dust, these values are the OSHA permissible exposure limit.
Health Hazard Evaluation Report 2014-0042-3216 Page 19

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Page 20 Health Hazard Evaluation Report 2014-0042-3216

Keywords: NAICS 336412 (Aircraft Engine and Engine Parts Manufacturing) Hydrogen 

Sulfide; Gas; Reactive Airways Dysfunction Syndrome (RADS); Wastewater; Electroplating.
Health Hazard Evaluation Report 2014-0042-3216 Page 21

The Health Hazard Evaluation Program investigates possible health hazards in the workplace 

under the authority of the Occupational Safety and Health Act of 1970 (29 U.S.C. § 669(a)

(6)). The Health Hazard Evaluation Program also provides, upon request, technical assistance 

to federal, state, and local agencies to investigate occupational health hazards and to prevent 

occupational disease or injury. Regulations guiding the Program can be found in Title 42, Code 

of Federal Regulations, Part 85; Requests for Health Hazard Evaluations (42 CPR Part 85).

Disclaimer 

The recommendations in this report are made on the basis of the findings at the workplace 

evaluated and may not be applicable to other workplaces.

Mention of any company or product in this report does not constitute endorsement by the 

National Institute for Occupational Safety and Health (NIOSH).

Citations to Web sites external to NIOSH do not constitute NIOSH endorsement of the 

sponsoring organizations or their programs or products. NIOSH is not responsible for the 

content of these Web sites. All Web addresses referenced in this document were accessible as of 

the publication date.

Acknowledgments

Desktop Publisher: Tia McClelland

Availability of Report

Copies of this report have been sent to the employer, employees, and union at the facility. The 

state and local health department and the Occupational Safety and Health Administration 

Regional Office have also received a copy. This report is not copyrighted and may be freely 

reproduced.

This report is available at http://www.cdc.gov/niosh/hhe/reports/pdfs/2014-0042-3216.pdf.

Recommended citation for this report:

NIOSH [2014]. Health hazard evaluation report: evaluation of Exposures 

and a Potential Hydrogen Sulfide Release Event at an Aircraft Engine 

Services Facility, West Virginia. By Armstrong JL, , Cummings KJ, Boylstein 

R, Ham J, Blackley D. Morgantown, WV: U.S. Department of Health and 

Human Services, Centers for Disease Control and Prevention, National 

Institute for Occupational Safety and Health, NIOSH HHE Report No. 

2014-0042-3216.
To receive documents or other information about

occupational safety and health topics, contact NIOSH

Telephone: 1-800-CDC-INFO (1-800-232-4636)

TTY: 1-888-232-6348

email: cdcinfo@cdc.gov

or visit the NIOSH website at http://www.cdc.gov/niosh

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