A Survey of Bakken Crude Oil Characteristics Assembled 

 For the U.S. Department of Transportation 

Submitted by 

American Fuel & Petrochemical Manufacturers 

Prepared by 

Dangerous Goods Transport Consulting, Inc. 

May 14, 2014 

 
2 

Table of Contents 

Executive Summary: Summary Table on Bakken Crude Oil Characteristics Evaluated in 

AFPM’s Survey 

I. Introduction 

II. Discussions on Transportation Considerations – Regulatory, Practice and Hazard 

Characteristics 

Definitions of gas and liquid; Reid Vapor Pressure (RVP); Degree of hazard; Packing 

Group; Flammability; Initial boiling point; DOT flammable liquid classification criteria; 

Emergency Response; Flammable gases dissolved in liquids; Hydrogen sulfide; Light 

crude oils; Bakken crude oil; Crude oil processing.

III. Survey Results 

A. Testing Used to Evaluate Bakken Crude Oils 

B. Test Methods Used to Characterize the Hazards of Crude Oil 

C. Reported Information and Test Results - Discussion and Range 

Flashpoint; Initial boiling point; Vapor pressure of crude oil in transportation, tank 

car pressures; Flammable Gas Content; Hydrogen sulfide content; Corrosivity to 

metals. 

D. Response to additional PHMSA Survey Question

IV. Summary Remarks 

Appendix 1 Questions Posed by PHMSA, January 29, 2014 

Appendix 2 PHMSA Field Office Questionnaire

Appendix 3 Paper submitted by Canada and the U.S. to the 45th session of the UN 

Subcommittee on the Transport of Dangerous Goods

Appendix 4 Test methods used to evaluate selected Bakken Crude Oil Characteristics 

Appendix 5 Guide page 128 from the 2012 Emergency Response Guidebook

Appendix 6 Glossary of Terms and Acronyms
3 

About the Author: This report has been prepared for AFPM by Frits Wybenga of Dangerous Goods Transport 

Consulting, Inc. Mr. Wybenga has more than forty years’ experience in the field of hazardous materials 

transportation. In 1971, he became the first U.S. Coast Guard officer with formal training related to hazardous 

materials in the Port of Houston, Texas. In succeeding years, he worked for the USCG in Washington, DC on 

matters dealing with technical and regulatory issues on safety and environmental protection relating to transportation 

of hazardous materials in bulk in tank barges, petroleum tank ships, chemical tankers, and liquefied gas carriers. 

Based on extensive technical and international experience, in 1989, he assumed responsibility for leading 

international activities on the transport of hazardous materials for the DOT Research and Special Programs 

Administration (subsequently renamed the Pipeline and Hazardous Materials Safety Administration). He served as 

the head of U.S. delegations to the United Nations Subcommittee of Experts on the Transport of Dangerous Goods 

(UNSCETDG) from 1989 to 2004 and served as the UN Subcommittee vice Chairman for 8 years. In 2000, he

became the Deputy Associate Administrator for Hazardous Materials Safety and remained in this position until 

retiring from DOT in 2005. Among other recognitions, his contributions to safety and environmental protection 

were recognized by two separate DOT Secretary Silver Metal Awards and two Hammer Awards signed by Vice

President Gore. Since retiring from his DOT position, he continues to participate in the UNSCETDG, representing a 

range of non-governmental organizations. He has degrees in chemical engineering, environmental engineering and 

business administration. He qualified as a registered professional engineer (chemical engineering) in the District of 

Columbia in 1974. He may be contacted at fwybenga@dg-transportation.com. 
4 

Executive Summary 

Recent incidents in the U.S. and Canada involving the transport of Bakken crude oil originating 

in North Dakota has focused considerable attention on the transportation of Bakken crude oil by 

rail. Questions have been raised as to whether Bakken crude oils pose substantially different 

risks than crude oils that have traditionally been transported. At the request of the Department of 

Transportation (DOT), the American Fuel & Petrochemical Manufacturers (AFPM) conducted a 

survey of its members to address questions posed by DOT and developed this report of its 

findings. In addition to obtaining responses to the questions DOT raised, as part of its survey, 

AFPM also collected data stemming from analysis of approximately 1400 samples of Bakken 

crude oil in order to better understand its properties. 

This report assembles AFPM member responses to questions posed by DOT and provides 

summary data on Bakken crude oil characteristics and hazards based on the sample information 

collected. The results show that Bakken crude oil may appropriately be classified as a 

flammable liquid based on DOT and international transportation requirements.1

 Comparison of 

assay data on Bakken crude oil with data from non-Bakken crude oils indicates that Bakken 

crude oil is within the norm with respect to the hazard characteristics of a light crude oil. While 

Bakken crude (and other light crudes) may contain higher amounts of dissolved flammable gases 

compared to some heavy crude oils, the percentage of dissolved gases would not cause Bakken 

crude to be transported under a DOT hazard class other than Class 3 Flammable Liquid and does 

not support the need to create a new DOT classification for rail transportation. Flammable gas 

content correlates with vapor pressure. The maximum vapor pressure observed based on data 

collected was 61% below the vapor pressure threshold limit for liquids under the HMR; 

demonstrating that Bakken crude oil is properly classified as a flammable liquid. With one 

exception, hydrogen sulfide concentrations were found to be extremely low – below the Short 

Term Exposure Limits for workers established by OSHA regulations. In the exceptional case, 

concentrations were substantially higher. Where they exist, high hydrogen sulfide 

concentrations are addressed under existing transportation and workplace safety regulatory 

provisions without affect to rail tank car authorizations. Data and experience indicate there to 

be no basis for classifying Bakken crude oil as having a corrosivity risk as defined by DOT 

Hazardous Materials Regulations.2 

The information provided confirms that Bakken crude oil does not pose risks significantly 

different than other crude oils or other flammable liquids authorized for rail transport. Bakken 

and other crude oils have been classified as flammable liquids. As noted, Bakken crude poses a 

lower risk than other flammable liquids authorized for transport by rail in the same specification 

tank cars. Measured tank car pressures show that even the older DOT 111’s authorized to 

 

1

 The United Nations Recommendations on the Transport of Dangerous Goods form the basis for DOT regulations 

and regulations used widely throughout the world. 

2

 Title 49 of the Code of Federal Regulations Parts 105 to 180. 
5 

transport Bakken crude oil are built with a wide margin of safety relative to the pressures that rail 

tanks may experience when transporting Bakken crude oil. 

Survey results are summarized below. Bakken crude oil currently is transported in compliance 

with the HMR as a Class 3 flammable Liquid in either Packing Group I, II, or III. In conclusion, 

there is no identifiable basis for regulating Bakken crude differently than other flammable liquids 

regulated by the DOT Hazardous Materials Regulations. 

Summary Table on Bakken Crude Oil Characteristics Evaluated in AFPM’s Survey 

Characteristic Reported Values Hazmat Transportation Regulatory 

Implications 

Flashpoint Range: -59oC to 50oC Bakken crude oils meet the criteria for Packing Group 

I, II, or III flammable liquids or as combustible liquids3 

Initial Boiling Point Range: 2.2oC to 66.9oC Bakken crude oils with an initial boiling point of 35 oC 

or less meet criteria for Packing Group I flammable

liquids; others for Packing Group II or III flammable 

liquids or combustible liquids according to flashpoint 

Vapor Pressure at 

50oC 

Maximum: 16.72 psia All Bakken crude oils have a vapor pressure below 43 

psia at 50oC and must be transported as liquids 

Reid Vapor Pressure 

at 38oC 

Maximum:15.4 psia Not used by the regulations; confirm the vapor 

pressure at 50oC is well below the above 43psia limit 

and Bakken crude oils must be transported as liquids. 

Rail tank car pressures 

on delivery 

Maximum:11.3 psig Demonstrates that Bakken crude may be safely 

transported in DOT specification 111 tank cars 4

Flammable gas 

content 

Maximum:12.0 liquid volume % None; with the vapor pressures of all Bakken crudes 

oils examined not exceeding a vapor pressure of 43 

psia at 50oC, all Bakken crude oils examined must be 

transported as liquids 

Hydrogen sulfide 

content in the vapor 

space 

Most reported H2S 

concentrations were below the 

OSHA STEL; one reported a 

maximum level of 23000 ppm 

None when low values are experienced; additional 

hazard communication to warn of the presence of H2S 

when inhalation hazard levels are encountered5

Corrosivity NACE B+ or B++ Data and experience indicate that Bakken crude oil 

does not corrode steel at a rate of 1⁄4 inch per year or 

more so that Bakken crude oil is not a corrosive liquid 

 

 

3 Note the Bakken crude data submitted included only one sample that qualified as a combustible 

liquid, which has a lower risk than other flammable liquids. 

4

 §179.201-1 provides summary specifications for DOT-111 rail tank cars. Earlier DOT 111’s were designed to a 

240 psig burst pressure whereas later designs are designed to a minimum burst pressure of 500 psig. Based on 

§179.15(b)(2)(ii) the minimum pressure relief valve settings for tank cars with a minimum burst pressure of 240 psig 

is 35 psig and for 500 psig designs the minimum setting is 75 psig. 

5

 See §172.327. 
6 

I. Introduction 

The American Fuel & Petrochemical Manufacturers (AFPM) is an industry association 

representing virtually all of the petroleum refiners and petrochemical manufacturers throughout 

the United States. The fuel and petrochemical manufacturing industries have a strong 

commitment to safety as well as environmental protection, and strive for opportunities to 

enhance safety and environmental protection. AFPM members depend upon a plentiful, 

affordable supply of crude oil as a feedstock for the transportation fuels and petrochemicals that 

they manufacture. Approximately 11 percent of the crude oil processed by AFPM members is 

transported by rail. 

As manufacturers, AFPM members acquire crude oils from multiple sources, including crude oil 

produced from the Bakken formation. Based on concerns expressed by the U.S. Department of 

Transportation (DOT) over the properties of Bakken crude oil being transported by rail, AFPM, 

at DOT’s request, conducted a survey of its members in an effort to characterize various hazard 

characteristics that could be relevant to the transportation of Bakken crude oils. For comparison 

purposes, the properties of crude oils from other fields were also considered. 

Bakken crude oil is derived primarily from northwestern North Dakota and to a lesser extent 

northeastern Montana, and the bordering Canadian provinces of Manitoba and Saskatchewan. 

Due to the lack of pipeline infrastructure, Bakken crude oil is transported extensively by rail. 

The data submitted in response to the survey demonstrates that Bakken crude oil is properly 

transported in accordance with the DOT Hazardous Materials Regulations (HMR) as UN1267 

Petroleum Crude Oil, or NA1993 Combustible Liquid, NOS. 

Survey Scope 

The initial questions posed to AFPM by DOT’s Pipeline and Hazardous Materials Safety 

Administration (PHMSA) on January 29 are attached in Appendix 1 to this report. PHMSA 

personnel in a regional office posed additional questions to AFPM members and these are 

attached in Appendix 2. These two sets of questions formed the basis for the survey conducted 

by AFPM. More recently, the experts from Canada and the United States to the United Nations 

Subcommittee of Experts on the Transport of Dangerous Goods submitted a formal document 

noting recent rail transport incidents involving Bakken crude oil and soliciting the input of the 

Subcommittee as to whether crude oil such as Bakken crude oil derived from fracking operations 

posed a different degree of risk than other crude oils.6

 To the extent possible this report also 

responds to questions raised in the UN paper. 

This report compiles information provided by 17 AFPM members who participated in the 

survey. Data analysis focused on Bakken crude oil as transported. Bakken data stems from 

sampling at loading points at well head locations, intermediate collection facilities (distribution 

 

6

 A copy of the UN Paper is reprinted in Appendix 3.
7 

centers) at which crude oil may be loaded into rail tank cars and at refinery locations taking 

receipt of crude oil after a rail journey. Data on approximately 1400 samples of Bakken crude 

oil was taken into account. 

II. Discussions on Transportation Considerations – Regulatory, Practice and 

Hazard Characteristics 

While PHMSA’s Bakken Blitz data collection is ongoing, PHMSA staff has suggested that 

Bakken crude oil is different from other crudes oils that have traditionally been transported by 

rail in the United States. The Canada/U.S. UN paper reiterates this opinion concerning Bakken 

crude oil stating, “[t]his mostly ‘younger’ crude is being found to contain significantly higher 

‘light ends’ than what has been traditionally transported as UN 1267.” Again referring to crude 

oils like Bakken crude oil, the UN paper goes on to suggest, “lighter crude oil with a higher 

quantity of dissolved flammable gases pose a significantly different risk than heavier crude oils 

that do not have such a high constituency of more volatile components.” Against this 

background, it may be instructive to first examine some relevant regulatory requirements, related 

crude oil hazard characteristics, and transport practices, particularly as they relate to Bakken 

crude oil. 

Definitions of gas and liquid.7

 The HMR base the definition of a gas on whether a substance is 

a gas at 20oC (68oF). Substances with a vapor pressure of more than 300 kPa (43.5 psia) at 50oC 

(122oF) are also considered as gases irrespective of whether any liquid is still present at that 

temperature. Substances that have a vapor pressure of not more 300 kPa (43.5 psia) at 50oC 

(122oF) and with a melting point at or below 20oC (68oF) are generally considered liquids. 

Crude oil, including Bakken crude oil, is properly classified as a liquid – irrespective of light end 

concentration – provided its vapor pressure is not more than 300 kPa (43.5 psia) at 50oC (122oF). 

The AFPM survey confirms that vapor pressures of Bakken crude oil are well below the 300 kPa 

at 50oC (122o

F) limit and are properly transported as liquids under the HMR. 

Reid Vapor Pressure (RVP). Reid vapor pressure is a common measure of a substance’s vapor 

pressure at 100o

F (38oC). The RVP of crude oil increases with the increasing presence of 

flammable gases and other volatile flammable liquid components (e.g., pentanes). 

Up until 1990, prior to harmonization of the HMR with international regulations, the HMR used 

RVP in place of the 300 kPa at 50oC (122oF) criterion for differentiating between a liquid and a 

gas.8 A substance with an RVP of 40 psia or less was regarded as a liquid. In addition, earlier 

editions used flashpoint and RVP as a basis for identifying authorized packagings, including 

authorized rail tank cars, for various flammable liquids. Then, §173.119 differentiated 

substances with an RVP of 16 psia or less from more hazardous substances with RVP’s between 

 

7

See 49 CFR § 171.8. 

8

 49 CFR §173.119 (1990 ed.). 
8 

16 and 27 psia and 27 and 40 psia; and used an RVP of 40 psia as the threshold for use of DOT 

specification 111 tank cars. It is noteworthy that Bakken crude oil RVP values obtained in this 

survey were all less than 16 psia so that the corresponding crude oils would all have been subject 

to earlier HMR packaging requirements appropriate for the two prior lowest hazard flammable 

liquid categories. 

RVP continues to be used by other regulatory agencies and the petroleum industry. For example, 

U.S Coast Guard (USCG) regulations for tank ships and tank barges still use a 40 psia RVP 

criterion for differentiating between liquids and gases in the case of petroleum products, 

including crude oils. The USCG regulations permit substances to be transported in integral tanks 

(i.e., gravity tanks not designed for any appreciable pressure) when regarded as liquids (i.e., RVP 

of 40 psia or less).9

Though no longer used in the HMR, the considerable information on the RVP of Bakken crudes 

serves to provide insight into the characteristics of crude oils derived from the Bakken formation. 

The current regulatory limit of 300 kPa at 50oC is only marginally different from RVP in the 

case of crude oils so that RVP values may be deemed a close approximation of the vapor 

pressure at 50oC (122o

F). 

Degree of hazard. The HMR vary the stringency of requirements according to the degree of 

risk various substances pose in transportation. Many hazards, including the flammability hazard 

of liquids, are subdivided into three risk levels: 

Packing Group I – encompasses substances regarded as posing a high hazard level; 

Packing Group II – encompasses substances regarded as posing a medium hazard level; and 

Packing Group III – encompasses substances regarded as posing a low hazard level. 

Packing Group as it pertains to rail transport. While Packing Group is commonly used in the 

HMR for purposes of tiering the severity of regulatory requirements, in the case of rail transport 

of crude oil, it should be noted that DOT 111 rail tank cars are authorized for transporting 

Packing Group I, II and III crude oils under UN1267.

10 DOT 111’s are widely used for 

transporting Bakken crude oil. While the HMR also authorize AAR Class 206 rail tank cars for 

Packing Groups II and III crude oil, these are legacy tank cars with few remaining in service. As 

such, Packing Group, in practice, has little to no impact on the integrity of rail tank cars used in 

transporting Bakken crude oil since DOT specification 111 tank cars are in common usage.11

 

DOT regulations and publications suggest that Packing Group is a secondary consideration in the 

case of emergency response. HMR placarding and rail tank car markings requirements, which 

are intended to communicate essential emergency response information, to emergency 

responders in the event of an accident or incident, do not communicate the Packing Group of the 

 

9

See 46 CFR §§ 30.10-22 (definition of a flammable liquid) and 30.10-39 (definition of a liquefied flammable gas). 

10 See 49 CFR §§ 173.242 and 173.243. 

11 For combustible liquids AAR 203W (less than 100) and 211W (less than 1100) tanks are also authorized. 
9 

hazmat involved. Further, the 2012 Emergency Response Guidebook (ERG)12 does not take 

Packing Group into account when advising emergency responders on immediate first response 

measures. 

The HMR require shippers to include the Packing Groups of hazardous materials on shipping 

papers and for rail transport this second level information for crude oil and other hazardous 

materials is available to emergency responders by accessing the train consist.13 Bakken crude is 

described on shipping papers (or the train consist) depending on Packing Group in the following 

concise well recognized format: 

- UN1267, Petroleum crude oil, 3, I; 

- UN1267, Petroleum crude oil, 3, II; or 

- UN1267, Petroleum crude oil, 3, III. 

When Bakken crude oil is transported in DOT 111 rail tank cars, as is common practice, the 

difference in shipping paper descriptions is the only regulatory difference distinguishing Packing 

Group I, II or III Bakken crude oils as they are transported by rail. 

Flammability. Flammable gases and vapors will ignite when they are mixed with air in certain 

concentration ranges. The lowest temperature at which flammable liquids produce vapor in 

sufficient amounts to support combustion is termed the liquid’s flashpoint. 

Under DOT and international regulations, a flammable liquid is a liquid that has a flashpoint of 

less than or equal to 60oC (140oF). Flammable liquids with a flashpoint of 23oC (73oF) or less 

are assigned to either Packing Group I or II. In essence, the flashpoint limits of 23oC (73oF) and 

60oC (140oF) for flammable liquids indicate whether a substance has: 

- Potential of producing a flammable vapor under moderate ambient temperature 

conditions – i.e., 23oC (73oF); or 

- Potential of producing a flammable vapor under the most extreme ambient temperature 

conditions – i.e., 60oC (140oF). 

Under the HMR, a flammable liquid with a flashpoint in the range of 38oC (100o

F) and 60oC 

(140oF) may also be regarded as a combustible liquid, reflecting that such substances have a 

lower risk of igniting. Combustible liquids also include liquids with a flashpoint up to 93oC 

(200o

F). 

Except for classification under the HMR, flashpoint is not commonly used to characterize crude 

oil. Testing for flashpoint is an inherently dangerous test to conduct even under controlled 

laboratory conditions. Given the specific threshold values in the HMR, measurement of an exact 

 

12 The ERG is periodically prepared and published jointly by DOT and the governments of Canada and Mexico. 

Registration fees collected from hazmat shippers and carriers in accordance with 49 CFR Subpart G support its wide 

distribution to emergency responders in the U.S. 

13 See 49 CFR §§ 172.202(a) and 174.26. 
10 

flashpoint value is not required. For compliance with the HMR, it is important to know what 

range of values the flashpoint of a particular crude oil falls into (e.g.; 23oC or less) – not the 

specific flashpoint value. For this purpose, approximation methods may be used (e.g.; 

chromatography or calculation methods). This may be common practice in the case of routine 

screening of crude oil shipments. Test methods identified by the HMR are typically not valid for 

substances below -30oC (-22oF); and approximation methods may have been used in producing 

some of the flashpoint data discussed in this report. 

While there is no regulatory limit on how low the flashpoint of a flammable liquid may be, 

diethyl ether, a Packing Group I flammable liquid transported as a pure substance, has a 

flashpoint of -45oC (-49oF). 

Initial boiling point. The HMR and international regulations use initial boiling point as a 

classification criteria. Boiling point is considered indicative of a substance’s volatility or its 

propensity to form flammable vapor plumes in air. Plume formation could occur after a spill of a 

flammable liquid when a fire is not involved. Increasing volatility leads to the formation of 

larger flammable vapor plumes. A lower boiling point generally implies increased volatility. As 

such, boiling point is used to evaluate the degree of risk a flammable liquid poses. The larger the 

flammable vapor plume a flammable liquid is capable of forming when spilled, the more 

dangerous it is considered to be, since the size of the plume affects the probability that 

flammable vapors will reach an ignition source and ignite. Predicting the size of a plume a 

particular liquid produces involves complex calculations accounting for ambient conditions and 

many other properties of a substance. Since boiling point is widely available, it is used as an 

approximation for gauging a substance’s volatility. The HMR use initial boiling point as the 

basis for a differentiating between substances that have a Packing Group I high hazard risk (i.e., 

an initial boiling point of less than 35oC (95o

F)) or a Packing Group II medium hazard risk. 

Pure substances have a single boiling point and boil off completely at one temperature. Mixtures 

of flammable liquids made up of various components, like crude oil, boil over a temperature 

range. The more volatile components (e.g., dissolved gases in the case of crude oils) will boil off 

at the initial boiling point leaving less volatile components with higher boiling points in the 

liquid. Increasingly higher temperatures are required to boil off remaining components. 

Subsequent less volatile and less dangerous (from a flammability perspective) fractions of a 

liquid mixture may not boil off until significantly higher temperatures are reached. An assay of a 

Bakken crude oil indicates a boiling point range spanning approximately 500oC. From a 

flammability/volatility perspective, in comparing a pure substance with a flammable liquid 

mixture with the same initial boiling point, the pure substance is more volatile and more 

dangerous. 
11 

DOT flammable liquid classification criteria. The HMR and international regulations classify 

flammable liquids into three Packing Groups as follows: 

Packing Group Flash point (closed-cup) Initial boiling point

I ≤35 °C 

(95 °F) 

II <23 °C (73 °F) >35 °C 

(95 °F) 

III ≥23 °C, ≤60 °C 

(≥73 °F, ≤140 °F) 

>35 °C 

(95 °F) 

 

Emergency Response. An important function of the HMR is to provide hazard information to 

emergency responders in the event of an accident or incident involving a hazardous material in 

transportation. The HMR hazard classification requirements result in the assignment a hazard 

class (e.g., flammable liquid), assignment of a UN number and proper shipping name and 

assignment of Packing Group. These determinations in turn lead to requirements for labeling 

and placarding to pictorially communicate the various HMR hazards, package markings to 

convey the UN number and proper shipping name, and shipping paper requirements providing 

additional information on the details of a hazardous material shipment. 

The 2012 Emergency Response Guidebook (ERG) is intended to supplement hazard 

communication information provided on packages and shipping papers. It is intended for use by 

emergency responders first arriving on the scene of an accident or incident. First responders 

include law enforcement personnel and fire department personnel – both professionals and 

volunteers. DOT distributes the ERG widely throughout the United States with the objective of 

making it available to every potential first responder. The frequency of hazardous materials 

accidents and incidents is rare so that on average a first responder is expected to encounter less 

than one incident in a career. As such information must be basic and understandable to those 

who have a low probability of encountering a hazardous materials accident or incident. 

The ERG serves this purpose. Through the UN number or proper shipping name of a substance, 

a first responder is able to access instructions on what steps to take upon arrival at the scene of 

an accident or incident. For crude oil assigned to UN 1267 Petroleum crude oil, irrespective of 

Packing Group, or crude oil meeting combustible liquid criteria and transported under NA 1993 

Combustible liquid, NOS, guide page 128 of the ERG provides a first responder with the 

appropriate information (see Appendix 5). In this respect, it is important to note that the range of 

crude oils subject to the HMR (i.e., crude oils of Packing Groups I, II and III and combustible 

liquid crude oils) are addressed by one set of instructions made available to first responders. The 

same guide page is applicable to many other flammable liquids independent of the degree of 

hazard. 
12 

Flammable gases dissolved in liquids. Gases typically dissolve to some degree in liquids. For 

a given temperature, the amount of gas that dissolves in a liquid is directly proportional to the 

partial pressure of the gas in equilibrium with the liquid. The amount of gas that can dissolve in 

a liquid increases with pressure and decreasing temperature. For this reason, soda in a bottle 

bubbles when the top is removed as carbon dioxide held in the liquid is released as a gas because 

the bottle pressure no longer holds the carbon dioxide in the liquid. The same happens with 

crude oil where flammable gases such as methane, ethane, propane and butane, held in solution 

under high pressure underground, are released as the pressure is decreased when it is brought to 

the surface and stored. If stored at a low temperature, crude oil will retain more gas than if 

stored at a higher temperature. 

Crude oil taken from the wellhead and placed in a stabilization tank continues to release 

dissolved gases until an equilibrium concentration between the gas dissolved in the crude oil and 

the concentration of the gas in the tank vapor space is reached. 

The DOT definition of a gas places a regulatory limit on the amount of flammable gas that may 

be held in crude oil in transportation. If a crude oil had a vapor pressure in excess of 300 kPa at 

50oC (122o

F) due to a high dissolved gas concentration, it would be regarded as a gas and not as 

a liquid. 

In some cases the HMR explicitly permit some quantities of certain gases to be transported in 

liquids. For example, up to 30% ethylene oxide (a toxic and flammable gas) may be transported 

in propylene oxide (a liquid) under UN 2983 Ethylene oxide and propylene oxide mixtures.

Hydrogen sulfide. In a pure form hydrogen sulfide is a gas and is regulated as a toxic and 

flammable gas under the HMR and OSHA regulations. Crude oil commonly contains some 

amount of sulfur. It may be present in hydrocarbon molecules (e.g., mercaptans) or as hydrogen 

sulfide dissolved in the liquid. The chemical/thermal and biological breakdown of the sulfur 

bearing hydrocarbon molecules in crude oil, as it is brought to the surface and is stored, may lead 

to increased evolution of hydrogen sulfide gas in crude oil liquid and vapor. 

When a crude oil contains concentrations of hydrogen sulfide at levels that may present an 

inhalation hazard, the HMR require communication of its presence. Bakken crude oil is 

generally considered a sweet crude and the survey data confirm that sulfur and hydrogen sulfide 

concentrations are normally low. However, exceptions were noted in the case of one respondent. 

Light crude oils. Light crude oils are generally regarded as those crude oils with an API gravity 

of 37 degrees or more. API gravity varies inversely with specific gravity so that increasing API 

gravity values reflect decreasing specific gravity or density. Light crudes tend to have higher 

concentrations of light ends (i.e., methane, ethane, propane, butanes and pentanes). The presence 

of increasing amounts of dissolved gases and other light ends (i.e., pentanes) has the effect of 

increasing the crude oil’s vapor pressure, lowering its flashpoint and lowering its initial boiling 

point. Light crude oils may qualify as Packing Group I, II or III flammable liquids under the 
13 

HMR depending on properties of the specific crude oil. Some may be transported as 

combustible liquids. Light crude oils are common throughout the world. Bakken crude oil is 

regarded as a light crude oil. 

Bakken crude oil. Bakken crude oil, like other crude oils, consists of a range of primarily 

hydrocarbon gases and liquids. The table below illustrates the composition of a Bakken crude oil 

sampled at a distribution center prior to loading for rail transportation. The table also provides 

the HMR classification for each component. Division 2.1 refers to the HMR flammable gas 

classification and Class 3 refers to the HMR flammable liquid classification. The particular 

Bakken crude oil sample depicted in the sample below had an RVP of 7.6 psia.14

Hydrocarbon 

gas 

Concentration in 

Liquid Volume % 

DOT Classification 

Methane <0.01 Div. 2.1 Gas 

Ethane 0.05 Div. 2.1 Gas 

Propane 0.80 Div. 2.1 Gas 

Iso-Butane 0.46 Div. 2.1 Gas 

N- Butane 2.36 Div. 2.1 Gas 

Total Gas 3.67 

Neopentane <0.01 Class3; PG I 

Iso-Pentane 1.33 Class 3; PG I 

N-Pentane 2.36 Class 3; PG II 

Hexanes 4.10 Class 3; PG II 

Heptanes Plus 88.56 Varies Class 3; PG II to 

combustible liquid to nonregulated 

Benzenes 0.08 Class 3; PG II 

For the same crude oil, the figure below provides the boiling point range. Note that the boiling 

point temperature progressively increases after the more volatile components are boiled off. 

 

14 Among assays of Bakken crude oil, 7.6 psia is a normal RVP value. 
14 

15

Consideration of flashpoint and boiling point data for hydrocarbons suggests that, for the crude 

oil illustrated, when 40% of the crude oil is boiled off, the remainder would not be regulated as a 

flammable liquid.16 As boiling continues beyond the 40% level, the remaining liquid would 

transition from a combustible liquid to a non-regulated substance. All else being equal, a pure 

flammable liquid with a boiling point comparable to the initial boiling point of the example 

crude oil would produce a flammable vapor plume 2.5 times larger than the example crude.17

 

While a rough comparison, it illustrates that pure substances may be considerably more volatile 

than flammable liquid mixtures with identical initial boiling points. 

The range of boiling points also suggests that in accident conditions where a tank is engulfed in 

flames, considerably more heat would be required to boil off the example crude oil than would 

be required of a pure substance with the same IBP. Consequently, based this and other factors, 

pressure buildup within a tank containing the example crude oil would be expected to be more 

gradual than that for a pure substance.

 

15 IBP values in this chart where based on ASTM 5307, a capillary chromatography method, producing lower values 

as compared to IBP data from samples provided which were based largely on ASTM D 86 – a method referenced in 

the HMR. 

16 Estimated based on the properties of n-dodecane, a C-12 hydrocarbon with a flashpoint of 71oC and a boiling 

point of 216oC, which is not subject to the DOT HMR as a flammable liquid. Crude oil compositions with a boiling 

point of 216oC or higher were assumed to not qualify as flammable liquids with a flashpoint less than 60oC. 

17 Some examples of other Class 3 Flammable Liquids that are transported in DOT 111’s with a higher 

risk profile than Bakken crude would include: diethyl ether, acrylonitrile, and ethyl mercaptan. 

0

10

20

30

40

50

60

70

80

90

100

-50 0 50 100 150 200 250 300 350 400 450 500 550 % Boiled Off

Boiling Temperature in ◦C

Boiling Point Range for Typical Bakken Crude
15 

Crude oil processing. When crude oil is extracted, it is typically processed to remove water and 

entrained gases, and stored in a tank prior to transportation. Processing, settling time in storage 

tanks and ambient temperature conditions all influence the extent to which light ends including 

gases are released from crude oil before it is transported. 

III. Survey Results 

A. Testing Used to Evaluate Bakken Crude Oils 

As a Class 3 flammable liquid or a combustible liquid under the HMR, Bakken crude oil is 

subject to evaluation of its flashpoint and initial boiling point for classification purposes in 

accordance with the HMR. Other tests evaluating vapor pressure, flammable gas content, 

hydrogen sulfide content and corrosivity are also employed by industry and provide additional 

information relative to the hazards of crude oil. 

Tests are carried out on crude oil samples taken at multiple locations along the distribution chain 

as it moves from the production point at a well to a refinery destination. Samples may be taken 

and evaluated at the well head, at gathering stations, at rail loading facilities, at pipeline facilities 

and when it is received at the refinery. Survey responses include data resulting from testing by 

AFPM members or independent laboratories (e.g. assays).18 Data considered relevant for 

purposes of this survey was limited to data characterizing crude oil “in transportation,” – ranging 

from data on samples taken at the well head location at the point of loading for transportation to 

data from samples taken where transportation ended at the refinery gate. 

Members generally found variations in properties of specific crude oils to be minimal as these 

crude oils moved through the distribution chain. Summary data provided in the survey 

aggregates data obtained for samples taken along the distribution chain. A number of members 

noted seasonal variations in some properties of Bakken crude oils. The variations may be 

attributable to higher retention of flammable gases in crude oils in winter owing to lower 

ambient temperatures. 

B. Test Methods Used to Characterize the Hazards of Crude Oil 

PHMSA requested information on test methods used to characterize crude oil. The test methods 

used to evaluate selected characteristics are provided in Appendix 4. 

 

18 Crude oil assays are detailed evaluations of crude oils that are commonly performed for commercial nonregulatory purposes. They may be used to define crude oil purchased by a refiner from a producer. The values 

reported in an assay reflect the properties of a specific sample. They are intended to represent characteristics of 

crude oils to be purchased and do not normally account for variations that may be identified among multiple 

samples. For example, higher RVP values for Bakken crude oil are noted in this survey for other samples. In 

addition, data from more than one assay was used in this report. Even though the data in assays are not normally 

used for regulatory compliance purposes, consideration of assay data was instructive for purposes of this survey 

given the detailed information they provide. 
16 

C. Reported Information and Test Results - Discussion and Range 

The following information on Bakken crude oil is based on responses from AFPM members and 

data provided on approximately 1400 samples of Bakken crude oils.19 The data included data 

points on specific characteristics as follows: 

Flash Point: 77 data points; 

Initial Boiling Point: 275 data points; 

RVP: 807 data points; 

Rail Tank Car Pressure (PSIG): 387 data points; 

Total C1-C4: 18 data points; 

H2S in Liquid: 37 data points; 

H2S in Vapor: 535 data points; and 

Corrosivity to metal: 7 data points.20

For comparison purposes data from samples of non-Bakken crude oil was also considered. 

1. Flashpoint 

Reported Bakken flashpoint range. Survey respondents reported flashpoints ranging from 

 -59oC (-74o

F) to 110oC (230oF). On the basis of this flashpoint information, Bakken crude oil in 

transportation ranges from being subject to regulation as flammable liquids (in all 3 Packing 

Groups), combustible liquids or not regulated as hazardous materials under the HMR. 

The chart below shows the distribution of flashpoints among all Bakken crudes for which data 

was provided as part of this survey. 

 

19 Many of the samples were collected in February/March 2014 in North Dakota. Given the prevailing 

ambient temperature, these samples are expected to represent “worst case” conditions that contribute 

to higher flashpoint, vapor pressure and dissolved gasses. 

20 Data provided was initially acquired for a range of purposes and not necessarily for compliance with the HMR. 

As such data on samples did not always include data points on all of the characteristics considered in the survey. 
Discussion on flashpoint data. Survey data indicate that

classification criteria for Packing Group

provided could be classified either 

As already noted, flashpoint data may be based on estimation methods with the objective of 

determining the HMR flashpoint 

these methods suffice for HMR classificati

appropriate flashpoint range they may not accurately reflect the 

would be obtained using a method identified as suitable under the HMR.

advised when considering specific values.

0

5

10

15

20

25

-60 to 

-50

-50 to 

-40

-40 to 

-30

Count

Flash Point Frequency for Bakken Crudes

Survey data indicate that 76 of the 77 crude oil sample

Packing Group I or II. One crude oil sample for which data was 

either as Packing Group III or as a combustible liquid.

As already noted, flashpoint data may be based on estimation methods with the objective of 

determining the HMR flashpoint range a particular crude oil falls into (e.g., 23oC or less). While 

classification purposes in that they assign a substance to the 

they may not accurately reflect the precise flashpoint value

would be obtained using a method identified as suitable under the HMR. As such caution is 

ering specific values.

40 to -30 to 

-20

-20 to 

-10

-10 to 

0

0 to 

10

10 to 

20

20 to 

30

30 to 

40

Flash Point Result (Deg C)

Flash Point Frequency for Bakken Crudes

Mean -27.1oC (-16.8oF) 

Median -36oC (-32.8oF) 

Mode -15.0 oC (5 oF) 

Minimum -59oC (-74.2oF) 

Maximum 50oC (122oF) 

17 

samples meet the 

for which data was 

a combustible liquid.

As already noted, flashpoint data may be based on estimation methods with the objective of 

C or less). While 

in that they assign a substance to the 

flashpoint value that 

As such caution is 

30 to 40 to 

50
2. Initial boiling point 

Reported Initial Boiling Points. 

that was provided on Bakken samples from crude oil in transportation.

Discussion on Initial Boiling Point information

majority of Bakken crude oils in transportation 

50oC. The low values shown in the lower 

upon arrival at a refinery in the months of February to April su

seasonal conditions. 

The HMR utilize an IBP threshold criterion of 35

Among Bakken crude oils, IBP values

Respondents to the survey noted 

While no misclassification is implied, 

value combined with repeatability 

challenges with respect to the assignment to 

3. Vapor pressure of crude oil in transportation, tank car pressures

Reported vapor pressure at 50oC

samples. The vapor pressure values ranged from a low of 13.89 psia to 16.72

RVP data these values appear to be in the high range of what would normally be expected

Bakken crude oil – although well below the vapor pressure threshold for a flammable gas

 The chart below describes the range of initial boiling point data 

that was provided on Bakken samples from crude oil in transportation. 

Mean 29.0oC (69.6o

F) 

Median 30.7oC (87.3oF) 

Mode 30.2 oC (86.4 oF) 

Minimum 2.2oC (36.0oF) 

Maximum 66.9oC (152.4oF)

n Initial Boiling Point information. Based on the data provided in the survey, t

in transportation have an initial boiling point ranging from

low values shown in the lower left hand side of the chart stem from samples taken 

upon arrival at a refinery in the months of February to April suggesting that IBP is influence

threshold criterion of 35oC to delineate between Packing Group

values are clustered around the regulatory threshold. 

noted problems with the variability and repeatability of 

While no misclassification is implied, the clustering of IBP values around the 35

repeatability problems associated with IBP testing could present 

assignment to Packing Group I or II. 

of crude oil in transportation, tank car pressures 

C. Vapor pressure values were reported in data on nine Bakken 

samples. The vapor pressure values ranged from a low of 13.89 psia to 16.72 psi

RVP data these values appear to be in the high range of what would normally be expected

although well below the vapor pressure threshold for a flammable gas

18 

The chart below describes the range of initial boiling point data 

Based on the data provided in the survey, the 

ing from 15oC to 

hand side of the chart stem from samples taken 

ggesting that IBP is influenced by 

Packing Group I and II. 

threshold. 

repeatability of IBP tests. 

of IBP values around the 35oC threshold 

present practical 

Vapor pressure values were reported in data on nine Bakken 

psia. Based on 

RVP data these values appear to be in the high range of what would normally be expected for 

although well below the vapor pressure threshold for a flammable gas. All 
but two samples were taken at the 

samples taken in February and March 

at other times during the year when ambient temperatures are higher.

Bakken crude oils fall within the d

the 300 kPa (43 psia) threshold value delineating between a gas and a liquid

Note that the vapor pressure at 50

reported RVP which is measured at 38

Reported Reid Vapor Pressure values

respondents and based on the data 

found to have RVP values ranging 

The chart below shows the distribution of RVPs among all Bakken crudes for which data was 

obtained as part of this survey. 

 

21 The seasonal variation of RVP is discussed below.

were taken at the rail loading point in North Dakota. These values were f

in February and March 2014. Lower vapor pressure values would be anticipated 

at other times during the year when ambient temperatures are higher.21 The data 

Bakken crude oils fall within the definition of a liquid under the HMR in that they are well below 

threshold value delineating between a gas and a liquid. 

Note that the vapor pressure at 50 oC will normally correlate closely with the far more widely 

is measured at 38 oC (100 oF) as discussed below. 

Reported Reid Vapor Pressure values (vapor pressure at 38 oC (100 oF)). Among the 

data submitted, Bakken crude oil offered for transportation

ranging from 0.8 to 15.54 psia.

The chart below shows the distribution of RVPs among all Bakken crudes for which data was 

The seasonal variation of RVP is discussed below.

19 

These values were from 

values would be anticipated 

The data confirm that 

in that they are well below 

C will normally correlate closely with the far more widely 

Among the survey 

Bakken crude oil offered for transportation was 

The chart below shows the distribution of RVPs among all Bakken crudes for which data was 
Seasonal variations of RVP. Seasonal variations of RVP are demonstrated in the following 

chart. 

The chart shows that RVP values 

psia during colder periods. RVP and other parameters are interrelated. As such, s

variations in other parameters such as flashpoint, init

are likely. 

Operational limits on crude oil RVP

operational limits on the RVP of crude oil. 

roof tanks. Environmental regulations governing the release of volatile organic compounds 

(VOCs) restrict the RVP (or a variant known as TVP measured at ambient temperature) of crude 

oil in floating roof tanks to 10-11 psia. The floating roof tank pressure l

RVP limits on the crude oil transported b

monitor crude oil for RVP to ensure compliance with

respondent noted that they test the RVP of

receipt. In their experience RVP values varied according to the time of year with RVP values as 

high as 15 psia in the winter and with lower RVP values typical in the summer. 

operational restriction on the transportation of

potential for pump cavitation. A limiting RVP of 10 psia was reported as typical for crud

transported by pipeline where pumping is required

crude oils transported by rail. Finally, l

operational perspective. One refinery respondent noted a contractual RVP limit of 9.5 psia. 

Seasonal variations of RVP are demonstrated in the following 

The chart shows that RVP values average 8 psia for warmer times of the year and average 12.5 

RVP and other parameters are interrelated. As such, s

such as flashpoint, initial boiling point, and flammable gas content 

Operational limits on crude oil RVP. Respondents noted that, outside of the HMR

operational limits on the RVP of crude oil. First of all, it is common to store crude oil in floating 

Environmental regulations governing the release of volatile organic compounds 

(VOCs) restrict the RVP (or a variant known as TVP measured at ambient temperature) of crude 

11 psia. The floating roof tank pressure limits impose practical 

transported by rail to refiners and petrochemical facilities.

monitor crude oil for RVP to ensure compliance with these environmental regulations.

respondent noted that they test the RVP of every rail shipment at the time of loading and upon

receipt. In their experience RVP values varied according to the time of year with RVP values as 

high as 15 psia in the winter and with lower RVP values typical in the summer. 

striction on the transportation of high RVP value crude oils is due to increased 

potential for pump cavitation. A limiting RVP of 10 psia was reported as typical for crud

where pumping is required. Pipelines are a destination for some Bakken 

Finally, lower RVPs are also more desirable from a refinery 

operational perspective. One refinery respondent noted a contractual RVP limit of 9.5 psia. 

20 

Seasonal variations of RVP are demonstrated in the following 

8 psia for warmer times of the year and average 12.5 

RVP and other parameters are interrelated. As such, similar seasonal 

ial boiling point, and flammable gas content 

the HMR, there are 

t is common to store crude oil in floating 

Environmental regulations governing the release of volatile organic compounds 

(VOCs) restrict the RVP (or a variant known as TVP measured at ambient temperature) of crude 

imits impose practical 

rail to refiners and petrochemical facilities. Recipients 

environmental regulations. One 

every rail shipment at the time of loading and upon

receipt. In their experience RVP values varied according to the time of year with RVP values as 

high as 15 psia in the winter and with lower RVP values typical in the summer. The second 

high RVP value crude oils is due to increased 

potential for pump cavitation. A limiting RVP of 10 psia was reported as typical for crude oils 

n for some Bakken 

ower RVPs are also more desirable from a refinery 

operational perspective. One refinery respondent noted a contractual RVP limit of 9.5 psia. 
21 

Reported rail tank car pressure measurements. The chart below indicates pressures measured in 

rail tank cars upon arrival at a refinery. The highest value reported was 11.3 psig. This value is 

lower than the 35 psig minimum relief valve setting for older DOT 111 rail tanks cars and their 

required 240 psig minimum design burst pressure. This suggests that DOT 111’s are built with 

an ample margin of safety relative to the pressures that rail tanks may experience when 

transporting Bakken crude oil. 

 

Mean 8.5 psig 

Median 8.5 psig 

Mode 9.0 psig 

Minimum 4.2 psig 

Maximum 11.3 psig

4. Flammable Gas Content 

Reported flammable gas concentrations. In response to the PHMSA question on ranges of 

flammable gas content of Bakken crude oil, respondents reported the following ranges:22

Hydrocarbon gas Concentration in Liquid Volume %

 

22 In data collected, some samples were found to have higher values than indicated in the range of 

values reported. Maximum values were 0.77 LV % for ethane, 3.4 LV % for propane, and 8.0 LV % 

for butane. As reflected in the bar chart below, based on sample data, the maximum total flammable 

gas content for all samples was 11.9 LV %. Samples were obtained in February and March. 

0 0 0 0 4 6

40

95 91

103

44

4

0

0

20

40

60

80

100

120

Count

PSIG Range

Rail Tank Car Pressure Frequencies (psig)
22 

Methane <0.01 

Ethane 0.50 

Propane <1-2% 

Iso-, N-Butane 3-4% 

Eighteen samples included measurements of flammable gas content. The information differs 

from light end content in that pentane, which is not a gas under the HMR, is commonly included 

in light end data. Data from three respondents indicated a maximum total flammable gas content 

(C1 to C4) of 3.5% Liquid Volume %. 

Information provided by a fourth respondent, included data from 12 samples taken in a one 

month period beginning in early February and ending in early March. In the case of the latter 

samples, total flammable gas content ranged from 5.9% to 11.9%. Ambient temperatures affect 

these gas concentration values. The data obtained from all respondents is illustrated in the chart 

below. 

2

4

0

3

1 1

2

0

2

3

0

1

2

3

4

5

2 - 3 3 - 4 4 - 5 5 - 6 6 - 7 7 - 8 8 - 9 9 - 10 10 - 11 11 - 12

Count

LV% Range

C1 Through C4 Frequency
23 

Comparison with other crude oils. To determine whether Bakken crude oil’s “light end” content 

is markedly different from other crude oils, data (primarily from assays) for other non-Bakken 

crude oils were examined.23 The table below illustrates that some selected other crude oils have 

comparable gas contents and in addition illustrates some of the variations in characteristics that 

exist among crude oils with a range of API gravities. (Note that “light ends” as the term is used 

in the petroleum industry includes pentanes which are deemed flammable liquids under the 

HMR.) Based on assay data for Bakken and non-Bakken crude oils24, the following table 

summarizes data obtained: 

 Crude Name Origin API RVP 

(psia)

Vol % of 

Light Ends 

(C2 – C5) 

Arabian Super 

Light 

Saudi Arabia 51 20.7 12.53 wt %25

(C1-C4 only) 

Eagle Ford Texas 48 7.95 8.3 

Agbami Nigeria 48 2.2 5.61 wt % 

DJ Basin Colorado 45 7.82 8.0 

Sarahan Blend Algeria 43 7.46 8.1 

Bakken North Dakota 42 7.83 7.2 

WTI Texas / New 

Mexico 

41 5.90 6.1 

Brent26 United Kingdom 37.5 9.33 5.28 wt % 

API gravity of 37 or more defines light 

crude oil 

37 

LLS Louisiana 36 4.18 3.0 

Alvheim blend Norway 34.9 3.9 1.86 wt % 

Arabian Heavy Saudi Arabia 28.4 18.3 5.13 wt % 

(C1-C4) 

Alberta Dilbit27 Alberta 21.1 7.18 7.30 wt % 

Alba United Kingdom 19.6 1.6 0.14 wt % 

 

23 Note “light ends” as the term is used in the petroleum industry includes pentanes which are deemed flammable liquids under the HMR.

24 Sources included data collected as part of the survey as well as online data at http://www.oiltransport.info/crudedata/crudeoildata/crudeoildata.html and data at 

http://www.statoil.com/en/ouroperations/tradingproducts/crudeoil/crudeoilassays/pages/default.aspx

25 Because the specific gravities of gases and pentanes in the liquid state are lower than that of other components, “wt %” is 

lower than “LV %”. Conversion from wt % to LV% requires the concentrations of each individual component. 

26 Data from a sample taken at the loading point. 

27 Data from a sample taken at the loading point. 
24 

Using assay data allows for evaluating oils on a consistent basis. While survey data on specific 

samples of Bakken crude oils (like other light crude oils) showed higher gas content than assay 

data, it may be expected that similar variations arise in the case of non-Bakken crude oils. The 

data suggests that Bakken crude oil is within the norm for what might be expected in the case of 

light end content in light crude oils. Light crudes oils are not unique to new drilling practices 

and have been common since the advent of petroleum extraction. 

Operational limits on flammable gas content. Since flammable gas content and vapor pressure 

are closely linked, operational limitations identified relative to RVP (i.e., floating roof tank 

limits, pipeline pumping limits and refinery operational considerations) also apply in the case of 

flammable gas concentrations. 

5. Hydrogen sulfide content

Reported hydrogen sulfide concentrations. Respondents indicated hydrogen sulfide vapor space 

concentrations were less than 10 ppm. 

Data reviewed was for either hydrogen sulfide concentration in the liquid or hydrogen sulfide 

concentration in the vapor. 

Data on H2S in liquid. For samples, hydrogen sulfide concentrations (in ppm) in the liquid were 

reported as follows: 

H2S in liquid Count 

x< 0.2 4

x<1.0 2

x< 2 22

x<5.0 1

x< 10 8

Total 37

These would suggest very low hydrogen sulfide vapor concentrations. 

Data on H2S in vapors. Reports of hydrogen sulfide (in ppm) in the vapor were reported as 

follows: 

H2S in Vapor Count 

x<1 390

x<2.0 9

x>2000 6

Total 535
25 

 

The above six values indicating “x>2000” stemmed from one of four respondents providing H2S 

vapor data. In addition, the same respondent reported 129 measured H2S values (in ppm) that are 

summarized as follows: 

H2S in Vapor 

Mean 3580

Median 2000

Min 1 

Max 23000

The data was based on samples taken at a gathering location where crude oil was being collected 

for transportation. For crude oils with H2S concentrations posing an inhalation hazard, 

additional HMR hazard communication requirements apply, including warnings on rail tanks 

cars.28

 

Operational limits on hydrogen sulfide. With an OSHA short term exposure limit (STEL) of 15

ppm for 15 minutes exposure, occupational limits are far below those warranting communication 

of the toxic hazard under the HMR. Where there is potential for exposure, employees are fitted 

with monitors and ambient air is subject to gas sampling. Testing for hydrogen sulfide is 

common for rail unloading operations and one respondent noted that hydrogen sulfide levels 

greater than 15 ppm were not allowed at company rail unloading facilities. Another respondent 

noted that where high hydrogen sulfide crude oils are encountered, the crude oil is typically not 

transported before first being subjected to treatment using amine scavengers. 

When appropriate, based on potential high levels of hydrogen sulfide which pose a health risk to 

workers, the risks of hydrogen sulfide are delineated on Safety Data Sheets.

6. Corrosivity to metals 

Discussion. Under the HMR, in addition to criteria for corrosivity to skin, a substance is 

regarded as corrosive if it corrodes steel or aluminum at a rate of 6.25 mm (0.25 inches) per year. 

A substance with this degree of corrosivity would penetrate steel used in crude oil rail tank cars 

in a period of approximately two years. There is no evidence that Bakken crude corrodes steel or 

aluminum at this rate. 

Reported corrosivity data. Data reported using NACE TM 172 indicates that Bakken crude oil 

scores as either B+ or B++ using this method. Generally, a NACE value of B+ or better is 

 

28 See 49 CFR §172.327. 
26 

required for transportation via pipeline. While crude oil does not meet the HMR corrosivity 

criteria, water, solids and H2S contaminants in crude may cause corrosion at rates less than that 

specified in the HMR for classification purposes. Industry deals with this lower level of 

corrosion from an asset management perspective. 

D. What safety information is provided to carriers? 

The HMR require that a considerable amount of information be provided to carriers, including: 

1. UN number of the crude oil; 

2. Proper shipping name under which it is transported; 

3. Hazard class (Class 3); 

4. Packing Group of the crude oil; 

5. Total quantity being offered or the number of packagings (i.e., rail tank cars) involved; 

6. Emergency response information that includes immediate hazards to health; risks of fire or 

explosion; intermediate methods to be taken for handling fires; initial methods for handling spills 

or leaks in the absence of a fire; and preliminary first aid measures; and 

7. A 24-hour emergency telephone number where more detailed information may be obtained. 

Upon request, carriers may also be provided material safety data sheets. 

IV. Summary Remarks 

Survey results obtained by AFPM members provide a considerable amount of information on 

which to assess the hazard characteristics of Bakken crude oil. The data obtained appears to be 

of good quality. From the data, it is clear that parameters such as vapor pressures, initial boiling 

points, flashpoints and dissolved gas content were influenced by seasonal variations. Yet even 

when considering data obtained during periods of cold weather, Bakken crude oil was found to 

be well within the limits for what is acceptable for transportation as a flammable liquid. Bakken 

crude oil was compared with other light crude oils and determined to be within the norm in the 

case of light hydrocarbon content, including dissolved flammable gases. 

Measured tank car pressures show that even the older DOT 111’s authorized to transport Bakken 

crude oil are built with a wide margin of safety relative to the pressures that rail tanks may 

experience when transporting Bakken crude oil. 

Other factors influence the properties of crude that is transported. As manufacturers, AFPM 

members have an interest in limiting the RVP for purposes of operational efficiency and 

adherence to Clean Air Act requirements. RVP values correlate with values for flammable gas 

content, initial boiling point and flashpoint. Levels of all these parameters, consistent with an 

RVP of approximately 10 psia or lower are in the best interests of AFPM members. Compliance 
27 

with OSHA requirements related to exposure to H2S also plays a role in reducing the hydrogen 

sulfide content of crude oil in transportation. 

AFPM and its members appreciate the concerns raised in relation to rail transport of Bakken 

crude oil and stand ready to work cooperatively with DOT and other governmental organizations 

to ensure the safe transportation of Bakken crude oil. This survey shows that Bakken crude oil 

does not pose risks that are significantly different than other crude oils and other flammable 

liquids authorized for transportation as flammable liquids. In some respects Bakken crude oil 

may be regarded as posing a lower degree of risk than other flammable liquids transported in 

accordance with the HMR, particularly pure substances.29

 

 

29 Some examples of other Class 3 Flammable Liquids that are transported in DOT 111’s with a higher 

risk profile than Bakken crude would include: diethyl ether, acrylonitrile, and ethyl mercaptan.
28 

Appendix 1 
29 
30 

Appendix 2 

PHMSA Field Office Questionnaire 

Company: Contact Name: __________________ 

Address: Title: 

City, State: Phone: 

Type: Refinery  Transfer Terminal  Email: 

• What tests, if any, are performed on the crude oil upon receipt? 

o How frequently are they completed? 

o Are you willing to share the results with us? 

• When you find high levels of gases in crude, what actions do you require of your 

personnel before unloading? 

o What information about the crude oil properties, if any, is provided by the 

offerors or carriers prior to receipt? 

o How is this information communicated? 

• Have you had to add any special safety measures or make any procedural changes in the 

unloading process to protect workers or modify the flow to the facility? 

• Are there any prescribed limits involving vapor pressure, flammable gas concentration or 

hydrogen sulfide content above which the crude oil is not accepted at terminal or 

refinery? 

o If so, what are these limits and how are they determined? (Note: We have heard 

that one of the larger refineries in Canada placed gauges on top of rail cars to 

measure pressure before unloading and in turn rejected some 400 rail cars.) 

 
31 

Committee of Experts on the Transport of Dangerous Goods 

and on the Globally Harmonized System of Classification 

and Labeling of Chemicals 

Sub-Committee of Experts on the Transport of Dangerous Goods 

Forty-fifth session 

Geneva, 23 June – 2 July 2014 

Item 4 (c) of the provisional agenda 

Listing, classification and packing: miscellaneous 

 Classification and hazard communication provisions for 

crude oil 

 Transmitted by the experts from Canada and the United States of 

America30

 Background 

1. North America is experiencing a significant increase in crude oil supply, bolstered 

both by growing production in the Canadian oil sands and the recent expansion of shale 

oil and natural gas production in the United States of America and Canada. 

2. North American shale oil and natural gas extraction has been mostly in geographic 

areas not linked to traditional crude oil or natural gas pipelines, resulting in an increase 

in surface transport. Surface transport has also enabled crude transport to different 

refinery capacities situated across North America. This mostly “younger” crude is being 

found to contain significantly higher “light ends” than what has been traditionally 

transported as UN 1267. 

 

30 In accordance with the programme of work of the Sub-Committee for 2013-2014 approved by the 

Committee at its sixth session (refer to ST/SG/AC.10/C.3/84, para. 86 and ST/SG/AC.10/40, para. 14). 

Appendix 3

United Nations ST/SG/AC.10/C.3/2014/49

Secretariat Distr.: General 

2 April 2014 

Original: English 
32 

3. This significant and exponential increased in surface movement of crude oil has led 

authorities within Canada and the United States of America to carefully consider 

transport safety impacts as well as potential impacts to the environment. These efforts 

have been prioritized based on a series of major accidents across North America 

involving crude oil transport by rail - including a catastrophic incident brought to the 

attention of the Sub-Committee at its previous session that caused numerous fatalities 

and destroyed much of Lac Mégantic, Quebec, in July 2013. 

4. The increased production and experience has led to a renewed focus within North 

America on assessing the adequacy of the current provisions governing crude oil 

transport. While an assessment of relevant rail operational conditions have been major 

components of this effort, a significant portion of the experience gained is relevant to all 

modes and would benefit from broader review and discussion within the SubCommittee. The purpose of this paper is to initiate discussions relevant to the 

experience recently gained, to raise important questions regarding the proper 

classification of - and transport provisions for – crude oil, and to invite the SubCommittee to consider whether a review of the existing UN entries, assigned 

classifications, and transport provisions is warranted. This discussion may also 

eventually encumber other petroleum products such as natural gas condensates. 

5. In particular, the Sub-Committee is invited to consider whether the current entries 

for crude oil in the Dangerous Goods List adequately distinguish between what can be 

significant variations in the flammable gas content of crude oils from different sources 

(see discussion below relevant to classification). 

 Discussion 

6. This document contains no proposals. The Sub-Committee is invited to provide 

feedback as a first step towards evaluating the efficacy of the current provisions of the 

Model Regulations based on an evolving understanding of the risks inherent in the 

transport of crude oil. Specifically, based on the information available on various types 

of crude oils in global transport today, the Sub-Committee is requested to provide 

feedback with respect to the classification and hazard communication elements of the 

Model Regulations currently applicable to crude oil. 

(a) Classification 

Unlike other Class 3 manufactured goods, organic materials from oil and 

gas production represent a unique challenge in regards to classification. 

Differences in the chemical makeup of the raw material can vary day-today and from well head-to-well head. Unprocessed crude oil may present 

unique hazards based on the specific dissolved gas content, posing 

different hazards in transport. Would further distinctions beyond merely 

identifying the Packing Group relevant to the flammable liquid hazard or 

the flammable gas content of the crude be appropriate to account for the 

differing hazards posed by what can be significant quantities of dissolved 

flammable gases? What is the most appropriate measure of this volatility 

– boiling point or vapour pressure? Is the proposed measurement method 

a calculation based on the properties of the material or an observed value? 

What are the most appropriate sampling and testing procedures? And 

finally, at what threshold should revisions to the regulatory requirements 

be considered? 

(b) Hazard communication 

The current flammable liquid entries in the Dangerous Goods List provide 

for a distinction in hazard by the assignment of Packing Groups based on 
33 

the liquid’s boiling and flash points. However, lighter crude oil with a 

higher quantity of dissolved flammable gases pose a significantly 

different risk than heavier crude oils that do not have such a high 

constituency of more volatile components. Would enhanced hazard 

communication distinguishing more volatile crude oils be beneficial for 

transport workers and emergency response personnel? If so, would a new 

table entry for such a material be sufficient? 

 Conclusion 

7. The Sub-Committee is invited to consider appropriate next steps to ensure that the 

provisions of the Model Regulations adequately address the risks posed by the transport 

of crude oil. Based on the feedback received at this session, the experts from Canada 

and the United States of America would be willing to prepare specific proposals for 

consideration at a future session.

 

_______________
34 

Appendix 4 

Test methods used to evaluate selected Bakken Crude Oil Characteristics 

1. Flashpoint (Note: Some reported using the methods referenced in §173.120(c).)

- ASTM D56 Standard Test Method for Flash Point by Tag Closed Cup Tester 

- ASTM D93 Standard Test Methods for Flash Point by Pensky-Martens Closed Cup 

Tester 

- ASTM D3278 Standard Test Methods for Flash Point of Liquids by Small Scale 

Closed-Cup Apparatus 

2. Initial boiling point (Note: Some reported using the methods referenced in 

§173.121(a)(2).)

- ASTM D86 Standard Test Method for Distillation of Petroleum Products at 

Atmospheric Pressure 

- ASTM D1160 Standard Test Method for Distillation of Petroleum Products at 

Reduced Pressure 

- ASTM D2887 Standard Test Method for Boiling Range Distribution of Petroleum 

Fractions by Gas Chromatography 

- ASTM D5134 Standard Test Method for Detailed Analysis of Petroleum Naphthas 

through n-Nonane by Capillary Gas Chromatography 

- ASTM D7169 Standard Test Method for Boiling Point Distribution of Samples with 

Residues Such as Crude Oils and Atmospheric and Vacuum Residues by High 

Temperature Gas Chromatography 

3. Vapor pressure 

- ASTM D2879 Standard Test Method for Vapor Pressure-Temperature Relationship 

and Initial Decomposition Temperature of Liquids by Isoteniscope 

- ASTM D5191 Standard Test Method for Vapor Pressure of Petroleum Products (Mini 

Method) 

4. Flammable gas content 

- ASTM D-5134 Standard Test Method for Detailed Analysis of Petroleum Naphthas 

through n-Nonane by Capillary Gas Chromatography 

- ITM 6008 Light ends analysis by Gas Chromatography 

- IP 344 Determination of light hydrocarbons in stabilized crude oils - Gas 

chromatography method 

5. Hydrogen sulfide content 

- ASTM D5705 Standard Test Method for Measurement of Hydrogen Sulfide in the 

Vapor Phase Above Residual Fuel Oils 
35 

- IP 507: Determination of boiling range distribution by gas chromatography method - 

Part 2: Heavy distillates and residual fuels 

- UOP163 Hydrogen Sulfide and Mercaptan Sulfur in Liquid Hydrocarbons by 

Potentiometric Titration 

6. Corrosivity to metal 

- NACE TM172 Standard Test Method - Determining Corrosive Properties of Cargoes 

in Petroleum Product Pipelines 

 
36 

Appendix 5 

Guide 128 from the 2012 ERG 

GUIDE 128 Flammable Liquids (Non-Polar/Water-Immiscible) 

POTENTIAL HAZARDS 

FIRE OR EXPLOSION 

• HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. 

• Vapors may form explosive mixtures with air. 

• Vapors may travel to source of ignition and flash back. 

• Most vapors are heavier than air. They will spread along ground and collect in low or confined areas (sewers, basements, tanks). 

• Vapor explosion hazard indoors, outdoors or in sewers. 

• Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. 

• Runoff to sewer may create fire or explosion hazard. 

• Containers may explode when heated. 

• Many liquids are lighter than water. 

• Substance may be transported hot. 

• For UN3166, if Lithium ion batteries are involved, also consult GUIDE 147. 

• If molten aluminum is involved, refer to GUIDE 169. 

HEALTH 

• Inhalation or contact with material may irritate or burn skin and eyes. 

• Fire may produce irritating, corrosive and/or toxic gases. 

• Vapors may cause dizziness or suffocation. 

• Runoff from fire control or dilution water may cause pollution. 

PUBLIC SAFETY 

• CALL EMERGENCY RESPONSE Telephone Number on Shipping Paper first. If Shipping Paper not 

available or no answer, refer to appropriate telephone number listed on the inside back cover. 

• As an immediate precautionary measure, isolate spill or leak area for at least 50 meters (150 feet) in all directions. 

• Keep unauthorized personnel away. 

• Stay upwind. 

• Keep out of low areas. 

• Ventilate closed spaces before entering. 

PROTECTIVE CLOTHING 

• Wear positive pressure self-contained breathing apparatus (SCBA). 

• Structural firefighters’ protective clothing will only provide limited protection. 

EVACUATION 

Large Spill 

• Consider initial downwind evacuation for at least 300 meters (1000 feet). 

Fire 

• If tank, rail car or tank truck is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, 

consider initial evacuation for 800 meters (1/2 mile) in all directions. 

EMERGENCY RESPONSE 

FIRE 

CAUTION: All these products have a very low flash point: Use of water spray when fighting fire may 

be inefficient. 

CAUTION: For mixtures containing alcohol or polar solvent, alcohol-resistant foam may be more 

effective. 

Small Fire 

• Dry chemical, CO2, water spray or regular foam. 

Large Fire 

• Water spray, fog or regular foam. 

• Do not use straight streams. 

• Move containers from fire area if you can do it without risk. 

Fire involving Tanks or Car/Trailer Loads 

• Fight fire from maximum distance or use unmanned hose holders or monitor nozzles. 

• Cool containers with flooding quantities of water until well after fire is out. 

• Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank. 

• ALWAYS stay away from tanks engulfed in fire. 

• For massive fire, use unmanned hose holders or monitor nozzles; if this is impossible, withdraw from
37 

area and let fire burn. 

SPILL OR LEAK 

• ELIMINATE all ignition sources (no smoking, flares, sparks or flames in immediate area). 

• All equipment used when handling the product must be grounded. 

• Do not touch or walk through spilled material. 

• Stop leak if you can do it without risk. 

• Prevent entry into waterways, sewers, basements or confined areas. 

• A vapor suppressing foam may be used to reduce vapors. 

• Absorb or cover with dry earth, sand or other non-combustible material and transfer to containers. 

• Use clean non-sparking tools to collect absorbed material. 

Large Spill 

• Dike far ahead of liquid spill for later disposal. 

• Water spray may reduce vapor; but may not prevent ignition in closed spaces. 

FIRST AID 

• Move victim to fresh air. 

• Call 911 or emergency medical service. 

• Give artificial respiration if victim is not breathing. 

• Administer oxygen if breathing is difficult. 

• Remove and isolate contaminated clothing and shoes. 

• In case of contact with substance, immediately flush skin or eyes with running water for at least 20 minutes. 

• Wash skin with soap and water. 

• In case of burns, immediately cool affected skin for as long as possible with cold water. Do not remove clothing if adhering to skin. 

• Keep victim warm and quiet. 

• Ensure that medical personnel are aware of the material(s) involved and take precautions to protect themselves 
38 

Appendix 6 

Glossary of Terms and Acronyms 

AFPM means the American Fuel & Petrochemical Manufacturers.

DOT means U.S. Department of Transportation. 

ERG means the Emergency Response Guidebook produced by PHMSA in cooperation with the 

governments of Canada and Mexico and used throughout North America as the basis for the 

initial response to a hazardous materials emergency.

Flashpoint means the lowest temperature at which a liquid or gas produces a concentration of 

vapor in air that may be ignited. 

H2S means hydrogen sulfide.

HMR the Hazardous Materials Regulations in 49 CFR Parts 105 to 180. 

IBP means initial boiling point. 

OSHA means the Occupational Safety and Health Administration.

PHMSA means the DOT Pipeline and Hazardous Materials Administration. 

Packing Group means the degree of hazard assigned to materials subject to the DOT HMR 

according to specified criteria. Hazard levels of Packing Group I (high), II (medium) and III 

(low) are possible. 

RVP means Reid Vapor Pressure. 

STEL means short term exposure limit for a specific substance in air. The value is commonly 

based on 15 minutes exposure. 

TVP means True Vapor Pressure. 

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