Evaluation of Potential Exposures 

to Railway Hazardous Material 

Inspectors 

HHE Report No. 2022-0049-3387 

August 2023 
Authors: Catherine C. Beaucham, PhD, CIH

Desktop Publisher: Shawna Watts

Editor: Cheryl Hamilton

Industrial Hygiene Field Assistance: Donnie Booher

Logistics: Kevin Moore

Keywords: North American Industry Classification System (NAICS) 926120 (Regulation and 

Administration of Transportation Programs), United States, Hazardous Materials, Railroad, 

Shipping

Disclaimer

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 USC 669a(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 CFR Part 85]. 

Availability of Report

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

and local health departments and the Occupational Safety and Health Administration Regional

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

Recommended Citation

NIOSH [2023]. Evaluation of potential exposures to railway hazardous material inspectors. By 

Beaucham C. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease 

Control and Prevention, National Institute for Occupational Safety and Health, Health Hazard 

Evaluation Report 2022-0049-3387, https://www.cdc.gov/niosh/hhe/reports/pdfs/2022-0049-

3387.pdf. 
Table of Contents

Main Report

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

Our Approach ................................................................................................................................................... 1

Our Key Findings.............................................................................................................................................. 2

Our Recommendations.................................................................................................................................... 2

Supporting Technical Information 

Section A: Workplace Information............................................................................................................ A-1

History of Issue at Workplace................................................................................................................ A-1

Process Description ................................................................................................................................. A-1

Section B: Methods, Results, and Discussion .......................................................................................... B-1

Methods: Document Review and Observations of Work Processes, Practices, and Conditions . B-1

Results: Document Review and Observations of Work Processes, Practices, and Conditions.... B-1

Methods: 4-Gas Meter............................................................................................................................. B-4

Results: 4-Gas Meter................................................................................................................................ B-4

Methods: Colorimetric Indicator Tubes ............................................................................................... B-4

Results: Colorimetric Indicator Tubes .................................................................................................. B-4

Discussion ................................................................................................................................................. B-4

Limitations................................................................................................................................................. B-5

Conclusions............................................................................................................................................... B-5
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1

Introduction

Request

Representatives of the American Federation of Government Employees Local 2814 requested a health 

hazard evaluation concerning potential exposures to hazardous material inspectors. Inspectors became 

concerned after experiencing accidental exposures to hazardous materials while inspecting railway 

shipping containers. The union wanted to find the best way to keep inspectors safe while they carried

out their duties.

Workplace

As part of hazardous material rail transportation 

protocols, federal hazardous material inspectors 

located throughout the nation perform random, 

unannounced inspections of the hazardous 

material shipping containers at railyards within 

their regions. The hazardous material inspectors 

will examine containers, including boxes, barrels, 

drums, tank cars, railcars, intermodal shipping 

containers, and other bulk containers, to 

determine compliance with regulations. 

Inspections include evaluating the classification 

and documentation of hazardous material 

shipments, as well as how they are packaged, 

marked, labeled, placarded, and loaded. 

Inspections may occur at the manufacturing site 

or at various railway transfer points (Figure 1).

To learn more about the workplace, go to Section A in the Supporting Technical Information

Our Approach

We visited four railyards to learn more about the job and employee health concerns. In August 2022, we 

visited two railyards near Chicago, Illinois, and another near Indianapolis, Indiana; and in October 2022, 

we visited a railyard near Cincinnati, Ohio. We completed the following activities during our evaluation: 

• Observed work practices. 

• Evaluated for the presence and levels of oxygen, hydrogen sulfide, and carbon monoxide, as 

well as the lower explosive limit (the meter senses the concentration of flammable or explosive 

gases to find the risk of fire or explosions) using a 4-gas meter. 

Figure 1. Rows of tank cars at the railyard, some 

containing hazardous materials, surrounded by 

active tracks. Photo by NIOSH.
2

• Tested for the presence of hazardous gases using a Dräger® pump with colorimetric indicator 

tubes that work for various hazardous materials. 

To learn more about our methods, go to Section B in the Supporting Technical Information

Our Key Findings

Inspectors could potentially be exposed to hazardous materials while inspecting

railway shipping containers

• Hazardous material inspectors encounter a wide variety of hazardous material. 

• Inspectors could be exposed if the hazardous material is not sealed correctly. 

• Inspectors cannot always predict the type of hazardous material to be inspected. However, to be 

better prepared, they can request the shipping manifest before the inspection. 

Four-gas meters would not reduce the inspectors’ risk of hazardous material 

exposure

• Inspectors could carry 4-gas meters while inspecting hazardous materials, but the meters are 

cumbersome and may provide a false sense of security. 

• Four-gas meters may encounter problems associated with cross-sensitivity with other materials. 

Plus, too many types of hazardous materials exist for the meters to be useful for this workplace.

Dräger pump and colorimetric indicator tubes would not reduce the risk of 

hazardous material exposure

• Inspectors encounter too many hazardous materials on a daily basis for the colorimetric 

indicator tubes to be useful. 

To learn more about our results, go to Section B in the Supporting Technical Information

Our Recommendations

The Occupational Safety and Health Act requires employers to provide a safe workplace.

Potential Benefits of Improving Workplace Health and Safety:

 Improved worker health and well-being  Enhanced image and reputation 

 Better workplace morale  Superior products, processes, and services

 Easier employee recruiting and retention  May increase overall cost savings
3

The recommendations below are based on the findings of our evaluation. For each recommendation, 

we list a series of actions you can take to address the issue at your workplace. The actions at the 

beginning of each list are preferable to the ones listed later. The list order is based on a well-accepted 

approach called the “hierarchy of controls.” The hierarchy of controls groups actions by their likely 

effectiveness in reducing or removing hazards. In most cases, the preferred approach is to eliminate 

hazardous materials or processes and install engineering controls to reduce exposure or shield 

employees. Until such controls are in place, or if they are not effective or practical, administrative 

measures and personal protective equipment might be needed. Read more about the hierarchy of 

controls at https://www.cdc.gov/niosh/topics/hierarchy/. 

We encourage the company to use a health and safety committee to discuss our 

recommendations and develop an action plan. Both employee representatives and 

management representatives should be included on the committee. Helpful guidance can be 

found in Recommended Practices for Safety and Health Programs at

https://www.osha.gov/shpguidelines/index.html. 

Recommendation 1: Improve and standardize inspectors’ hazardous material 

education and training on materials they might encounter

Why? Providing inspectors with more information about the hazardous materials they might 

encounter can help protect them because they could be exposed to the materials they inspect. All the 

inspectors we observed had different procedures for carrying out their inspections.

How? At your workplace, we recommend these specific actions:

Improve inspector education and training about the hazardous material

they might encounter. 

• Standardize the inspection approach that hazardous material inspectors follow to train 

on best practices and reduce potential exposures.

• Train and require inspectors to accurately identify the type of hazardous material

contained in the tank car or intermodal containers before inspecting. 

• Work with occupational safety and health professionals to develop a plan in case of an 

accidental exposure with hazardous material. 

• Train all inspectors on the new inspection approach. 
4

Recommendation 2: Improve policies and procedures for emergency situations

Why? Providing inspectors with policies and procedures for emergency situations involving 

hazardous materials can help prepare and protect them. Understanding policies and procedures 

specific to the emergency situations encountered (for example, accidentally breathing in hazardous 

materials or having contact with skin) could keep the hazardous material inspectors safer. 

How? At your workplace, we recommend these specific actions:

Develop policies and procedures for emergency situations. 

• Define the types of emergency situations being planned for, such as a spill or hazardous 

material release, then develop policies and procedures specifically for these emergency 

situations. 

• Include these types of emergency situations in the Job Hazard Analysis (which are 

written procedures to help workers understand and lower hazards in job tasks) for 

hazardous material inspectors. This should be specific to the hazardous material

inspectors’ work, and include details of additional precautions that should be taken in an 

emergency.

• Train inspectors at least annually on how to respond to an emergency, including details

of how and when to evacuate the area. Identify and practice specific response strategies 

for the most likely exposure scenarios.
Supporting Technical Information

Evaluation of Potential Exposures to Railway

Hazardous Material Inspectors 

HHE Report No. 2022-0049-3387 

August 2023
A-1

Section A: Workplace Information

History of Issue at Workplace

In 2008, an inspector was inspecting railroad tank cars containing hazardous material (HM) when a 

partially open ball valve sprayed methylene diphenyl diisocyanate in the inspector’s face. An additional 

report of exposure occurred in 2019 when an inspector inhaled methyl isobutyl carbinol vapors while 

inspecting a tank car and became ill. Lastly, in 2020, an inspector opened the protective housing cover 

while inspecting a railroad tank car and inhaled anhydrous ammonia.

To address these exposures and prevent future incidents, a union representative suggested the 

possibility of inspectors using 4-gas meters to evaluate the air around the tank cars before they begin 

their inspections. The 4-gas meter detects oxygen (O2), carbon monoxide (CO), hydrogen sulfide (H2S), 

and lower explosive limit (LEL); however, they are typically used for confined space entry. In 2021, the 

federal railroad industrial hygiene team accompanied HM inspectors in four districts on 152 tank car 

inspections. The HM inspectors wore either a 4-gas meter or a 4-gas meter with a photoionization 

detector (PID). In addition to the previously mentioned four gases, the PID also detects certain volatile 

organic compounds (VOCs) that can be ionized by ultraviolet photons. No alarm events occurred 

during their evaluation, even when a tank car had a noticeable ethanol leak. 

Process Description

At the time of our evaluation, there were about 48 HM inspectors located throughout the United States. 

During our evaluation, we worked with four HM inspectors at four railyards: two near Chicago, Illinois, 

one near Indianapolis, Indiana, and one near Cincinnati, Ohio. The railcars containing HM that the 

inspectors examined during our evaluation included pressure tank cars, non- or low-pressure tank cars, 

and intermodal shipping containers. The list of types of HM in the tank cars was vast and included the 

following (identification number followed by name): 

• 1010 butadiene

• 1017 chlorine

• 1075 liquified petroleum gas

• 1110 n-amyl methyl ketone

• 1123 butyl acetates

• 1129 butyraldehyde

• 1173 ethyl acetate

• 1247 methyl methacrylate

• 1789 hydrochloric acid

• 1814 potassium hydroxide, solution
A-2

• 1830 sulfuric acid

• 1831 sulfuric acid, fuming

• 1942 ammonium nitrate

• 1987 alcohols (ethanol)

• 1993 flammable liquids, not otherwise stated (nos)

• 3265 corrosive liquid, nos

• 3272 esters, nos

• 3295 hydrocarbons, liquid nos

Tank Cars

To complete the HM inspection of the tank car, inspectors first identified a train track that had HMcontaining tank cars. Railroad tank cars (pressurized, non-pressurized, or low-pressure) were typically 

cylindrical and included top fittings with filling and inspection ports located inside a protective housing

(Figure A2). In addition, most of the cars had a bottom outlet valve. Another type of tank car was more 

rectangular with multiple outlets on the bottom of the car (Figure A3).

Figure A2. Cylindrical hazardous 

materials tank car. Photo by NIOSH.

Figure A3. Squared tank car containing 

ammonium nitrate. Photo by NIOSH.

All inspectors scanned the railyard for Department of Transportation (DOT) placards that indicated the 

presence of HM. Only one of the inspectors we observed went to the railyard main office to request the 

Hazmat Training listing, a report that contained the specific chemical name and required safety 

precautions for the types of HM in the yard. After identifying the cars, the inspector requested the track 

be “blue flagged,” meaning that no rolling stock may be moved past that point. This was done to 

protect the inspector’s safety while performing the inspection.
A-3

All inspectors noted the United Nations (UN) classification. The inspector verified that the DOT 

Placard with the UN number was visible on all sides of the railcar. They then ensured that the outlet 

valves on the bottom of the car were hand tight (Figure A4). After a visual inspection of the outside of 

the car (for rust, damage, leaks, etc.) the inspector proceeded to climb to the top the car. Inspectors 

noted the wind direction and tried to stand upwind of the top fitting housing. They removed the sealing 

tag, opened the housing, and waited for an unspecified time to allow for off-gassing. They then 

evaluated the valves inside of the housing to ensure they were in good condition and sealed hand tight

(Figures A5 and A6). Lastly, they closed the housing and reaffixed a metallic zip tie to show that it had 

been inspected and was now resealed.

Figure A4. The hazardous materials inspector examines valves at the bottom of the tank car. Photo by NIOSH. 

Figure A5. Inside the valve housing on top of the tank railcar containing hazardous materials. Photo by NIOSH.
A-4

Figure A6. Inside the protective housing on the top of the tank car. Photo by NIOSH.

Intermodal Shipping Containers 

After the inspector identified an intermodal container with HM, the inspector noted the DOT Placard 

and UN number. The inspector attached a strap to the back of the container so that when it opened, 

the contents (which may have shifted during transportation) did not fall onto the inspector (Figure A7). 

The inspector then removed the metallic zip tie and opened the container. All intermodal containers are 

inspected from the outside because they are considered confined space, and the inspectors are not 

permitted to enter (Figure A8). After inspection, the inspector resealed the intermodal container with a 

zip tie. 

Figure A7. HM inspector affixing a strap 

to the back of the intermodal container. 

Photo by NIOSH.

Figure A8. Inspection of an intermodal 

shipping container containing hazardous 

materials. Photo by NIOSH.
B-1

Section B: Methods, Results, and Discussion

Methods: Document Review and Observations of Work Processes, Practices, and 

Conditions

Prior to our visit, we reviewed the Hazard Communication Program, Job Hazard Analysis for the 

inspectors, Field Orientation Training Guide, Hazardous Materials Compliance Manual, “Safe at 

Work,” and the OSHA 301 forms. During our visits to the four different railyards, we observed the 

work processes, individual practices, personal protective equipment usage, and workplace conditions as

the HM inspectors conducted unannounced inspections of railway tank cars and intermodal shipping 

containers.

Results: Document Review and Observations of Work Processes, Practices, and 

Conditions

Document Review

The Hazard Communication Program appropriately recognized HM inspectors as requiring Hazard 

Communication Training. The Field Orientation Training Guide had descriptions of which inspectors 

were required to receive DOT Hazmat Training (regarding packaging and shipping of HM), and these

included HM inspectors. The Hazardous Materials Compliance Manual outlined the job duties, types of 

investigations, and basic safety practices that HM inspectors were to follow. For intermodal containers, 

these practices included using a safety strap before opening the door, waiting several minutes for an air 

exchange to take place inside of cars, not entering permit-required confined spaces, and not handling

leaking HM packages. For tank cars, basic safety practices included allowing 15 to 20 seconds to pass 

for built-up HM vapor to escape the housing. Inspectors were instructed not to proceed with the 

inspection if the inspector felt unsafe to do so (e.g., slippery surfaces). 

The “Safe at Work” document described required personal protective equipment, including this

statement regarding respiratory protection: “Inspectors are presently not assigned to tasks that would 

require the use of respirators due to exposure on the job.” This document also stated to stand upwind

from the valves and to “guard yourself as you begin to lift a protective housing cover” due to vapor 

accumulation. This document also stated that inspectors should “rely on your senses when approaching 

any container,” and that “visible leakage, detectable odors, or audible sounds” may help identify the 

presence of problems relating to HM. 

The Job Hazard Analysis document included a section on how to react to a “respiratory injury” if a leak

or spill was discovered on cars carrying hazardous chemicals. Although the HM inspectors are not first 

or emergency responders, the Job Hazard Analysis recommended that inspectors access information 

about spilled materials in the Emergency Response Guidebook found at 

https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/ERG2016.pdf. Lastly, the OSHA 301 

forms described two incidents of accidental exposure to HM. We did not review any document that

recommended HM inspectors identify the specific type of HM in the container prior to the inspection.
B-2

Observations of Work Process, Practices, and Conditions 

During the inspection of tank cars containing HM, an inspector encountered a damaged valve that

could cause leakage around the seal (Figure B9). During another tank inspection, the inspector found a 

valve that was not closed “hand tight.” Upon further inspection, it was discovered that the valve 

threading had been stripped, likely because someone had used a tool to attempt to seal the valve. This 

damaged valve could no longer seal tightly, allowing fumes and vapors from inside the tank to expose 

the HM inspector (Figure B10). During this inspection, a prominent odor was detected. The inspector 

notified the yard master of these noncompliant cars to prevent them from departing.

Figure B9. Valve inside the housing 

with a damaged seal on the valve 

cover. Photo by NIOSH.

Figure B10. An open valve inside of 

the housing. Photo by NIOSH.

Some cars that contained inhalation hazards were clearly labeled as such (e.g., the chlorine car in Figure 

B11). However, for other tank cars that contained inhalation hazards, the information was not as

obvious. For example, Figure B12 shows a tank car filled with fuming sulfuric acid, which is both 

corrosive and an acute inhalation toxicity. However, for this tank, the “fuming” label was covered with 

a magnet (Figure B13). Therefore, the only way to know that the contents were fuming sulfuric acid was 

to look up the UN number (1831) on the DOT placard. Because these tank cars can be used to 

transport both fuming and non-fuming sulfuric acid, the magnet was likely in place for a previous time 

when the car was filled with non-fuming sulfuric acid.
B-3

Figure B11. Chlorine tank car labeled inhalation hazard, including the inhalation pictogram on the DOT placard. 

Photo by NIOSH.

Figure B12. A tank car labeled “Sulfuric Acid” displaying a DOT placard with UN Number 1831 and the corrosive 

chemical pictogram. Photo by NIOSH.

Figure B13. A magnet covering the word “fuming” on the label of the tank car. Photo by NIOSH.
B-4

Methods: 4-Gas Meter 

We used the Gas-Clip® Technologies 4-gas meter with sensors for O2, CO, H2S, and LEL. Oxygen 

meters alert for both oxygen-rich and oxygen-deficient environments. When sensors for toxic gases 

such as CO and H2S are installed, an alert will sound well before preset hazardous concentrations are 

reached. The LEL sensor detects the concentration of flammable or explosive gases to determine the 

risk of fire or explosions.

Results: 4-Gas Meter

There were no alarm events during any of the HM inspections. The LEL sensor never detected 

anything above zero, even when there were detectable odors.

Methods: Colorimetric Indicator Tubes 

We used Dräger® colorimetric single-gas detector tubes with a bellows pump to collect air samples 

inside the protective housings on top of the railcars. Colorimetric indicator tubes are chemical specific 

and are manufactured for over 350 different gases and vapors. The detector tubes have a standard 

measuring range based on the chemical of interest. We inserted the tip of the indicator tube into closed 

housing through a “viewport” and used the bellows pump to pull a calibrated quantity of air through 

the tube. If the chemical of interest was detected within the standard range, the chemical reagent inside 

the tube would change colors, measuring the concentration present in the housing. We used the five 

“hydrocarbon” indicator tubes, ranging from 10–300 parts per million (ppm), for railcars containing 

petroleum hydrocarbons. We also used two “ethanol” indicator tubes for alcohols (100–3,000 ppm) for 

railcars containing alcohols.

Results: Colorimetric Indicator Tubes

One of the five hydrocarbon indicator tubes had a detectable 

result of approximately 50 ppm (Figure B14). Once the housing 

was opened, there was a strong odor that dissipated after about 

2 minutes. This was the inspection that had the stripped valves.

None of the other indicator tubes showed a color change.

Discussion 

The transportation of HM throughout the United States is 

essential to the economy. Therefore, hazardous material

inspectors can expect to encounter a wide variety of HM each 

day. No device can detect every type of HM to which the 

inspector could potentially be exposed. For example, 4-gas 

meters can only detect the chemicals or conditions

corresponding with the installed sensors (e.g., O2, CO, H2S, and 

LEL). In addition, 4-gas meters are typically used for contained 

activities such as confined space entry. The open-air environment 

on top of a tank car would likely dilute the sample, making 

Figure B14. Colorimetric indicator tube 

for petroleum hydrocarbons showing 

~50 ppm. Photo by NIOSH.
B-5

concentrations below the detectable limit even if the chemicals were present. Although the 4-gas meters 

provide real-time monitoring for the specified gases in the environment, the possibility exists for 

compounds in the environment to interfere with the electrochemical sensors, resulting in erroneously 

high or low readings due to cross sensitivity.

Although the PID detects a wider range of VOCs, it does not measure common toxic gases (e.g., CO, 

hydrogen cyanide, sulfur dioxide), natural gas (methane and ethane), acid gases (hydrochloric acid, 

hydrogen fluoride, nitric acid, etc.), and non-VOCs such as polychlorinated biphenyls. In addition, the 

accuracy of the sensor can be affected by rain and humidity, potentially causing false readings.

Considering the previously mentioned limitations, we do not recommend inspectors carry a 4-gas meter 

or PID. Carrying the device would add to the burden of the HM inspector and could provide a false 

sense of security while performing inspections.

Limitations 

This evaluation is subject to limitations. During the assessment we could not recreate a HM release; 

therefore, we do not know if the LEL sensor would detect an actively leaking flammable chemical. In 

addition, we could not evaluate all the types of HM that inspectors might encounter nor all the 

environments and weather conditions in which they work.

Conclusions

It is possible for HM inspectors to be exposed to a variety of HM while inspecting shipping containers, 

which includes tank cars and box cars. Using a 4-gas meter, with or without a PID, or using 

colorimetric indicator tubes, would not protect inspectors during these inspections. Increasing hazard 

communication training, anticipating the type of HM they will be inspecting, and preplanning 

emergency response scenarios would better protect the inspectors.
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Promoting productive workplaces through safety 

and health research

HHE Report No. 2022-0049-3387