Changes to Consider in the 

Federal Motor Carrier Safety Regulations and 

North American Standard Inspection Procedures 

to Accommodate Hydrogen as an 

Alternative Fuel 

Final Report 

 November 2007
FOREWORD 

PURPOSE 

Today, virtually all commercial trucks are powered by diesel fuel, while private cars are fueled 

by gasoline. Supported by our National Energy Policy, a new generation of technologies is 

currently being developed that allow the use of hydrogen as a fuel to power cars and trucks. The 

purpose of this document is to provide a review of existing Federal Motor Carrier Safety 

Regulations (FMCSRs) with respect to changes that should be considered to accommodate 

commercial vehicles that use hydrogen as an alternative fuel. In addition, this document also 

provides a review of the existing North American Standard (NAS) Inspection Procedures and 

considers changes in those procedures that should be considered for inspections of commercial 

vehicles using hydrogen as an alternative fuel. 

NOTICE 

This document is disseminated under the sponsorship of the Department of Transportation in the 

interest of information exchange. The United States Government assumes no liability for its 

contents or the use thereof. 

The contents do not necessarily reflect the official policy of the Department of Transportation. 

This report does not constitute a standard, specification, or regulation. 

The United States Government does not endorse products or manufacturers. Trade or 

manufacturers’ names appear herein only because they are considered essential to the objective 

of this document. 
TECHNICAL REPORT DOCUMENTATION PAGE 

Technical Report Documentation Page (Form 1700.7) 

1. Report No.

FMCSA-RRT-07-027

2. Government Accession No. 3. Recipient's Catalog No. 

4. Title and Subtitle: 

Changes to Consider in the Federal Motor Carrier Safety Regulations and 

North American Standard Inspection Procedures to Accommodate 

Hydrogen As an Alternative Fuel – Final Report 

5. Report Date: 

December 4, 2007

6. Performing Organization Code 

MC-RRT 

7. Author(s): 

John M. Simon, CSP, Booz Allen Hamilton Inc. 

Stephen Brady, Booz Allen Hamilton Inc. 

Dana Lowell, M. J. Bradley & Associates 

8. Performing Organization Report No. 

9. Performing Organization Name and Address: 10. Work Unit No. (TRAIS) 

Booz Allen Hamilton Inc. 

444 S. Flower Street, Suite 1850 

Los Angeles, California 90071 11. Contract or Grant No. 

GS-23F-0025K 

13. Type of Report and Period Covered:

Final Project Report

12. Sponsoring Agency Name and Address: 

U.S. Department of Transportation 

Federal Motor Carrier Safety Administration 

Technology Division 

1200 New Jersey Ave. SE 

Washington, DC 20590 

14. Sponsoring Agency Code 

FMCSA 

15. Supplementary Notes: 

Contracting Officer’s Technical Representative: 

 Quon Y. Kwan, Program Manager 

16. Abstract: 

Over the next 50 years, hydrogen use is expected to grow dramatically as an automotive and electrical power source 

fuel. As hydrogen becomes commercially viable, the safety issues associated with hydrogen systems, equipment, and 

operation are of concern to the commercial motor vehicle industry. This report provides a review of the existing 

Federal Motor Carrier Safety Regulations (FMCSRs) and considers changes in order to accommodate gaseous and 

liquid hydrogen. In addition, this report considers changes to the current North American Standard (NAS) 

Inspection Procedures to accommodate gaseous and liquid hydrogen used as an alternative fuel in commercial 

vehicles. 

17. Key Words: Guidelines for use of Hydrogen Fuel 

regulations, rules, inspection procedures, commercial vehicles, hydrogen, 

compressed hydrogen gas, liquefied hydrogen, alternative fuel, trucks, buses, 

hydrogen safety, driver awareness training 

18. Distribution Statement 

No restrictions. 

19. Security Classif. (of this report) 

 Unclassified 

20. Security Classif. (of this page) 

 Unclassified 

21. No. of Pages: 

35 

22. Price 

N/A 
SI* (MODERN METRIC) CONVERSION FACTORS 

APPROXIMATE CONVERSIONS TO SI UNITS APPROXIMATE CONVERSIONS FRO

Symbol When You Know Multiply By To Find Symbol Symbol When You Know Multiply By 

LENGTH LENGTH 

in Inches 25.4 millimeters Mm mm millimeters 0.039 incft Feet 0.305 meters M m meters 3.28 feeyd Yards 0.914 meters M m meters 1.09 Yami Miles 1.61 kilometers Km km kilometers 0.621 mi

AREA AREA 

in2 square inches 645.2 square millimeters mm2 mm2 square millimeters 0.0016 squft2 square feet 0.093 square meters m2 m2 square meters 10.764 squyd2 square yards 0.836 square meters m2 m2 square meters 1.195 squac Acres 0.405 hectares Ha ha hectares 2.47 acrmi2 square miles 2.59 square kilometers km2 km2 square kilometers 0.386 squ

VOLUME VOLUME 

fl oz fluid ounces 29.57 milliliters Ml ml milliliters 0.034 flugal Gallons 3.785 liters L l liters 0.264 gaft3 cubic feet 0.028 cubic meters m3 m3 cubic meters 35.71 cuyd3 cubic yards 0.765 cubic meters m3 m3 cubic meters 1.307 cu

MASS MASS 

oz Ounces 28.35 grams G g grams 0.035 oulb Pounds 0.454 kilograms Kg kg kilograms 2.202 poT short tons (2000 lbs) 0.907 megagrams Mg Mg megagrams 1.103 sho

TEMPERATURE (exact) TEMPERATURE (exac

°F Fahrenheit 5(F-32)/9 Celsius °C °C Celsius 1.8 C + 32 

Temperature or (F-32)/1.8 temperature temperature 

ILLUMINATION ILLUMINATION 

fc foot-candles 10.76 lux Lx lx Lux 0.0929 fl foot-Lamberts 3.426 candela/m2 cd/m2 cd/m2 candela/m2 0.2919 

FORCE and PRESSURE or STRESS FORCE and PRESSURE or S

lbf pound-force 4.45 newtons N N newtons 0.225 psi pound-force per square inch 6.89 kilopascals kPa kPa kilopascals 0.145 

* SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. 
ACKNOWLEDGEMENTS 

This document was prepared by Booz Allen Hamilton Inc., and M.J. Bradley & Associates, Inc., 

under contract GS-23F-0025K with the Federal Motor Carrier Safety Administration (FMCSA), 

a subdivision of the U.S. Department of Transportation (DOT). The FMCSA project manager for 

this project was Mr. Quon Kwan, and the Booz Allen Hamilton project manager and principal 

author of this document was Mr. John Simon, supported by Mr. Dana Lowell of M.J. Bradley & 

Associates. 

The authors would like to thank Mr. William Chernicoff of the DOT Research and Innovative 

Technology Administration for lending his expertise to help guide the project. The authors would 

also like to thank the following organizations and individuals for hosting project team members 

and providing background information and valuable insights: the California Highway Patrol, 

Commercial Vehicle Section, Mr. Chris Morgan and Mr. Mike Chafee; and the Commercial 

Vehicle Safety Alliance, Collin Mooney, Director of Enforcement Programs and Steve Keppler, 

Director of Policy and Programs. 
TABLE OF CONTENTS 

ACRONYMS...............................................................................................................................III

EXECUTIVE SUMMARY ........................................................................................................ IV

1. INTRODUCTION.................................................................................................................1

2. HYDROGEN FUEL CONSIDERATIONS........................................................................2

3. FMCSR REVIEW.................................................................................................................3

4. 49 CFR PARTS 392.50, 393.27, 393.28, AND 393.65.........................................................4

5. BASES FOR CONSIDERING CHANGES TO FMCSRS AND NAS INSPECTION 

PROCEDURES.....................................................................................................................6

5.1 GAPS IN EXISTING FMCSRS WITH RESPECT TO FUELS THAT ARE LESS 

DETECTABLE AND MORE FLAMMABLE THAN DIESEL FUEL .......................6 

5.2 GAPS IN EXISTING FMCSRS WITH RESPECT TO PRESSURIZED GASEOUS 

AND CRYOGENIC LIQUID FUELS ..........................................................................7 

5.3 CURRENT PRACTICES IDENTIFIED TO INSPECT ALTERNATIVE-FUELED 

VEHICLES....................................................................................................................8 

6. CONSIDERING CHANGES TO FMCSRS FOR GASEOUS HYDROGEN................9

7. CONSIDERING CHANGES TO FMCSRS FOR LIQUID HYDROGEN ...................12

8. NORTH AMERICAN STANDARD (NAS) INSPECTION PROCEDURES ...............14

8.1 BASIS FOR CONSIDERING CHANGES TO NAS INSPECTION PROCEDURES15 

9. CONSIDERING CHANGES TO INSPECTION PROCEDURES FOR GASEOUS 

HYDROGEN.......................................................................................................................16

10. CONSIDERING CHANGES TO INSPECTION PROCEDURES FOR LIQUID 

HYDROGEN.......................................................................................................................19

11. CONSIDERING CHANGES TO NAS OUT OF SERVICE ORDERS.........................22

12. SUMMARY/CONCLUSION.............................................................................................23

i 
LIST OF APPENDICES 

APPENDIX A: CALIFORNIA HIGHWAY PATROL INSPECTION PROCEDURES 

FOR COMPRESSED NATURAL GAS AND LIQUEFIED NATURAL GAS ............24

REFERENCES.............................................................................................................................26

LIST OF TABLES 

Table 1. Inspection Levels ............................................................................................................ 15 

LIST OF FIGURES 

Figure 1. California Highway Patrol Inspection Checklist—Form CHP 353A............................ 24 

Figure 2. California Highway Patrol Inspection Checklist—Form CHP 354 .............................. 25 

ii 
ACRONYMS 

CHP California Highway Patrol 

CNG Compressed Natural Gas 

FMCSA Federal Motor Carrier Safety Administration 

FMCSR Federal Motor Carrier Safety Regulation 

FMVSS Federal Motor Vehicle Safety Standards 

LNG Liquefied Natural Gas 

NAS North American Standard for commercial vehicle inspections 

NFPA National Fire Protection Association 

NHTSA National Highway Traffic Safety Administration 

PRD Pressure Relief Devices 

PRV Pressure relief valve; a device used to protect from overpressure inside a highpressure storage tank 

psi Pounds per square inch; a unit of measure for pressure 

psig Pounds per square inch gauge; gauge pressure is measured relative to 

atmospheric air pressure at sea level, so that gauge measurements of atmospheric 

pressure at sea level are always 0 psig 

SAE Society of Automotive Engineers 

iii 
EXECUTIVE SUMMARY 

Over the next 50 years, hydrogen use is expected to grow dramatically as an automotive and 

electrical power source fuel. As hydrogen becomes commercially viable, the safety concerns 

associated with hydrogen systems, equipment, and operation are of concern to the commercial 

motor vehicle industry. This report provides a review of the existing Federal Motor Carrier 

Safety Regulations (FMCSRs) that pertain to fueling systems and considers changes in order to 

accommodate gaseous and liquid hydrogen. In addition, this report considers changes to the 

current North American Standard (NAS) Inspection Procedures to accommodate gaseous and 

liquid hydrogen used as an alternative fuel in commercial vehicles. 

iv 
1. INTRODUCTION 

This report provides a review of existing Federal Motor Carrier Safety Regulations (FMCSRs) 

overseen by the FMCSA to determine what, if any, modifications should be considered in 

existing regulations in order to accommodate the use of hydrogen fuel in the commercial vehicle 

sector. The primary FMCSR that governs commercial vehicle fuel systems is 49 CFR Part 

393.65. This report also considers how commercial vehicle inspections and carrier reviews may 

need to be modified to address commercial vehicles that use hydrogen as an alternative fuel. 

Examples of hydrogen fuel system equipment that are different from traditional fueled vehicles 

include: 

• Pressure relief devices 

• Venting stacks 

• High-pressure fuel tanks (compressed hydrogen) 

• Cryogenic fuel tanks (liquid hydrogen) 

• Leak detection systems 

• Numerous other special features depending on fuel cell type, reformer technology, fuel 

storage approach, and other manufacturer-specific design features 

A separate report provides information on the types of hydrogen fuel systems and components 

that could be expected for use in the commercial vehicle sector (see Guidelines for Use of 

Hydrogen Fuel in Commercial Vehicles, FMCSA, dated 2007). 

1 
2. HYDROGEN FUEL CONSIDERATIONS 

In order to promulgate safety regulations for the use of hydrogen as an alternative fuel, one must 

have a basic understanding of the properties of hydrogen (see Guidelines for Use of Hydrogen 

Fuel in Commercial Vehicles, FMCSA, dated 2007 for additional details on the properties of 

hydrogen). Hydrogen as a fuel has unique physical and chemical properties that are different 

from traditional automotive fuels. These properties have specific hazards associated with them 

including: 

• Hydrogen is not readily detectable by human senses. Hydrogen is colorless, odorless,1

and tasteless. Therefore, systems and equipment are required to detect the presence of 

hydrogen in the event of a leak. 

• Hydrogen has a high flammability for two reasons. As compared to other automotive 

fuels, hydrogen has a much wider range of flammable concentrations in air. Second, 

hydrogen has one of the lowest ignition energy levels of automotive fuels. 

These two hazards of hydrogen are the fundamental principles that were considered in reviewing 

existing safety regulations and identifying the need for modifying or developing new safety 

regulations. 

In addition to the above issues related to the properties of hydrogen, one must also have an 

understanding of the form in which hydrogen is likely to be stored and used on the vehicle. Due 

to the low energy content of hydrogen, using hydrogen as a fuel requires onboard storage in 

compressed gas or liquid form in order to provide sufficient range for vehicle systems. 

Consequently, the storage of hydrogen onboard vehicles can introduce additional hazards such as: 

• High Pressure – Hydrogen is most likely to be stored on the vehicle as a high-pressure 

gas, at pressures up to 10,000 pounds per square inch. 

• Extremely Low Temperature – Hydrogen may also be stored on the vehicle as a 

cryogenic liquid at temperatures below -423°F. 

The understanding and consideration of the hazardous properties discussed thus far form the 

basis for safely using hydrogen as an alternative fuel, and will shape appropriate considerations 

for changes in the regulations. Consideration of changes in FMCSA regulations that address 

hazards related to the form in which hydrogen is stored on the vehicle will be similar if not 

identical to those by NHTSA in the FMVSS regulations dealing with other high-pressure gases 

or cryogenic liquids used as automotive fuels (for example, compressed natural gas or liquefied 

natural gas). Of the fuel properties unique to hydrogen, the most important with respect to safety 

regulations are those related to detection by human senses (odorless, colorless, invisible flame) 

and hydrogen’s very high flammability. 

 

1 Other gases used as automotive fuel, for example natural gas, are also naturally odorless. However, sulfur-based odorants are typically 

added to pipeline natural gas to aid in detecting a leak. These odorants are incompatible with the catalysts used in automotive fuel cells and 

substitute odorants have not been developed. 

2 
3. FMCSR REVIEW 

The FMCSR requirements for “All Fuel Systems” are listed in 49 CFR Parts 392.50, 393.27, 

393.28, and 393.65 as shown in section 4.0 of this report. Based on the review of this existing 

regulation, it is apparent that significant modifications are required for commercial vehicles that 

use hydrogen as an alternative fuel. Specifically: 

• In general, the regulations are written for commercial vehicles using diesel fuel and do 

not address alternative fuels. 

In particular, the regulations do not consider safety systems and equipment regulations required 

for commercial vehicles using hydrogen as an alternative fuel (e.g., requirements for grounding 

and bonding fueling connections). 

3 
4. 49 CFR PARTS 392.50, 393.27, 393.28, AND 393.65 

49 CFR 392.50, Ignition of fuel; prevention. 

No driver or any employee of a motor carrier shall: 

(a) Fuel a commercial motor vehicle with the engine running, except when it is necessary to run the engine to fuel the 

commercial motor vehicle; 

(b) Smoke or expose any open flame in the vicinity of a commercial motor vehicle being fueled; 

(c) Fuel a commercial motor vehicle unless the nozzle of the fuel hose is continuously in contact with the intake pipe of the fuel 

tank; 

(d) Permit, insofar as practicable, any other person to engage in such activities as would be likely to result in fire or explosion. 

49 CFR 393.27, Wiring specifications. 

 (a) Wiring for both low voltage (tension) and high voltage (tension) circuits shall be constructed and installed so as to meet

design requirements. Wiring shall meet or exceed, both mechanically and electrically, the following SAE Standards as found in 

the 1985 edition of the SAE Handbook: 

(1) Commercial vehicle engine ignition systems-SAE J557-High Tension Ignition Cable. 

(2) Commercial vehicle battery cable-SAE J1127-Jan 80-Battery Cable. 

(3) Other commercial vehicle wiring-SAE J1128-Low Tension Primary Cable. 

(b) The source of power and the electrical wiring shall be of such size and characteristics as to provide the necessary voltage as 

the design requires to comply with FMVSS 571.108. 

(c) Lamps shall be properly grounded. 

NOTE: This shall not prohibit the use of the frame or other metal parts of a motor vehicle as a return ground system provided 

truck-tractor semitrailer/full trailer combinations are electrically connected. 

49 CFR 393.28 

Electrical wiring shall be installed and maintained to conform to SAE J1292-Automobile, Truck, Truck-Tractor, Trailer, and Motor 

Coach Wiring, October 1981, except the jumper cable plug and receptacle need not conform to SAE J560. The reference to 

SAE J1292 shall not be construed to require circuit protection on trailers. (See §393.7(b) for information on the incorporation by 

reference and availability of this document.) 

49 CFR 393.65 

(a) Application of the rules in this section. The rules in this section apply to systems for containing and supplying fuel for the 

operation of motor vehicles or for the operation of auxiliary equipment installed on, or used in connection with, motor vehicles. 

(b) Location. Each fuel system must be located on the motor vehicle so that -- 

(b)(1) No part of the system extends beyond the widest part of the vehicle; 

(b)(2) No part of a fuel tank is forward of the front axle of a power unit; 

(b)(3) Fuel spilled vertically from a fuel tank while it is being filled will not contact any part of the exhaust or electrical systems of 

the vehicle, except the fuel level indicator assembly; 

(b)(4) Fill pipe openings are located outside the vehicle's passenger compartment and its cargo compartment; 

(b)(5) A fuel line does not extend between a towed vehicle and the vehicle that is towing it while the combination of vehicles is in 

motion; and 

(b)(6) No part of the fuel system of a bus manufactured on or after January 1, 1973, is located within or above the passenger 

compartment. 

(c) Fuel tank installation. Each fuel tank must be securely attached to the motor vehicle in a workmanlike manner. 

(d) Gravity or syphon feed prohibited. A fuel system must not supply fuel by gravity or syphon feed directly to the carburetor or 

injector. 

(e) Selection control valve location. If a fuel system includes a selection control valve which is operable by the driver to regulate 

the flow of fuel from two or more fuel tanks, the valve must be installed so that either -- 

(e)(1) The driver may operate it while watching the roadway and without leaving his/her driving position; or 

(e)(2) The driver must stop the vehicle and leave his/her seat in order to operate the valve. 

 

4 
49 CFR 393.65 (continued) 

(f) Fuel lines. A fuel line which is not completely enclosed in a protective housing must not extend more than 2 inches below the 

fuel tank or its sump. Diesel fuel crossover, return, and withdrawal lines which extend below the bottom of the tank or sump must 

be protected against damage from impact. Every fuel line must be -- 

(f)(1) Long enough and flexible enough to accommodate normal movements of the parts to which it is attached without incurring 

damage; and 

(f)(2) Secured against chafing, kinking, or other causes of mechanical damage. 

(g) Excess flow valve. When pressure devices are used to force fuel from a fuel tank, a device which prevents the flow of fuel from 

the fuel tank if the fuel feed line is broken must be installed in the fuel system. 

[36 FR 15445, Aug. 14, 1971, as amended at 37 FR 4341, Mar. 2, 1972; 37 FR 28752, Dec. 29, 1972] 

5 
5. BASES FOR CONSIDERING CHANGES TO FMCSRs AND 

NAS INSPECTION PROCEDURES 

The consideration of changes to the Federal Motor Carrier Safety Regulations and North 

American Standard Inspection Procedures to accommodate hydrogen as an alternative fuel 

contained in this report are based on three factors: 

• The wide flammability range of hydrogen and inability of the unaided human senses to 

detect hydrogen leaks require more stringent measures than those currently being taken 

with diesel fuel. 

• Gaps identified in existing Federal Motor Carrier Safety Regulations (FMCSRs) with 

respect to pressurized gaseous and cryogenic liquid fuel systems. 

• Current practices identified to inspect alternative-fueled vehicles. 

Each of these factors is discussed below. 

5.1 GAPS IN EXISTING FMCSRs WITH RESPECT TO FUELS THAT ARE LESS 

DETECTABLE AND MORE FLAMMABLE THAN DIESEL FUEL 

As compared to diesel, hydrogen has properties that should be considered in the FMCSRs, 

mainly: 

• Hydrogen leaks onboard a commercial vehicle using hydrogen as an alternative fuel 

cannot be detected by human senses. The inability to detect hydrogen leaks means that 

other measures are required for commercial vehicle using hydrogen as an alternative fuel. 

• A hydrogen flame has very low luminosity and is nearly invisible or undetectable in 

daylight conditions. 

• Hydrogen has a wider flammability range than diesel. A wider flammability range means 

that hydrogen poses a greater fire hazard than diesel. 

• Hydrogen has a lower ignition energy than diesel. A lower ignition energy means that 

hydrogen can be ignited easier than diesel. 

As a result of these differences, more stringent requirements should be added to the existing 

FMCSRs to accommodate the use of hydrogen as an alternative fuel in commercial vehicles. 

Specific changes discussed in the following sections of this report include the need for the 

requirement for hydrogen leak detection systems, grounding and bonding, and prohibition 

against the use of cell phones during fueling. 

6 
5.2 GAPS IN EXISTING FMCSRs WITH RESPECT TO PRESSURIZED GASEOUS 

AND CRYOGENIC LIQUID FUELS 

Based on current hydrogen fuel technology, there are two ways that hydrogen that may be stored 

as an alternative fuel: 

• Compressed hydrogen—The most common form of hydrogen fuel stored onboard 

vehicles today is compressed hydrogen. In order to get enough fuel onto a vehicle to be 

able to go several hundred miles between fill-ups, but without taking up too much space, 

the hydrogen must be stored at very high pressure. Most current vehicle systems store 

hydrogen at a pressure of 5,000 pounds per square inch (psi). 

• Liquefied hydrogen—In order to increase a vehicle’s range, some manufacturers of 

hydrogen systems are considering storing hydrogen onboard in liquefied form. The 

boiling point of hydrogen at atmospheric pressure is -423°F; above that temperature, 

hydrogen exists as a gas, and it will only liquefy if the temperature drops below the 

boiling point. Compressors and heat exchangers can be used to lower the temperature of 

hydrogen gas to produce liquid hydrogen, which must then be kept at this very low 

temperature or it will “boil off” again as a gas. To maintain its temperature, liquid 

hydrogen is stored in specialized, heavily insulated, containers called “dewars,” 

“cryotanks,” or “cryogenic vessels.” 

A detailed discussion of hydrogen onboard storage can be found in the FMCSA report entitled 

“Guidelines for Use of Hydrogen Fuel in Commercial Vehicles.” 

These two forms of hydrogen fuel are considered the most common forms of hydrogen that are 

used as an alternative fuel and form one of the bases for considering revisions in the FMCSRs 

for accommodating hydrogen as an alternative fuel. 

Based on a review of the existing regulations, several key elements are missing with respect to 

hydrogen and gaseous fuels in general. 

• There are currently no FMCSRs for compressed gaseous fuels. 

• Currently, there are no FMCSRs that pertain to cryogenic or super-cooled liquid fuels. 

Based on increased environmental considerations to operate cleaner commercial vehicles, some 

fleet operators are investigating hydrogen and natural gas as an alternative to diesel. It is readily 

apparent from a review of the existing regulations that new regulations need to be developed for 

the vehicles using these types of alternative fuels. 

7 
5.3 CURRENT PRACTICES IDENTIFIED TO INSPECT ALTERNATIVE-FUELED 

VEHICLES 

Another important factor that contributed to the consideration of regulatory changes contained in 

this report was a review of inspection practices currently deployed to regulate and inspect 

alternative-fueled vehicles. As part of this project, a site visit was made to the California 

Highway Patrol (CHP), Commercial Vehicle Section, located in Sacramento, California. The 

CHP has developed a comprehensive program to inspect compressed natural gas (CNG) and 

liquefied natural gas (LNG) commercial vehicles operating in California. The CHP inspection 

program includes developing detailed CNG and LNG inspection checklists from NFPA 52 and 

57 fire codes, and providing on-the-job training for field inspectors. Based on this review, the 

CHP inspection procedures for vehicles using natural gas, either liquefied or compressed, could 

serve as a model for inspection of commercial vehicles using hydrogen as an alternative fuel 

(note: The CHP had not updated its checklist to conform to the most recent NFPA edition [NFPA 

52] at the time of our visit). A copy of the CHP’s inspection procedures is contained in appendix 

A of this report. 

8 
6. CONSIDERING CHANGES TO FMCSRs FOR 

GASEOUS HYDROGEN 

To properly regulate gaseous hydrogen-fueled commercial vehicles, specific regulations should 

be considered for gaseous hydrogen. The following areas should be considered for inclusion into 

updated regulations: 

1. Vehicle Labeling 

a. Requirement for “diamond “ type labeling of commercial vehicle as a gaseous hydrogen 

fueled vehicle: 

– Label (consistent with Society of Automotive Engineer [SAE] J2578, Recommended 

Practice for Hydrogen Vehicles) 

– Location (suggested in tow locations on opposing sides of vehicle cab) 

– Label Size (suggested readable at 50 ft) 

2. Fuel Components and Tank Labeling (e.g., similar to requirements of 49 CFR 571.304 for 

compressed natural gas (CNG) tanks but applied to gaseous hydrogen tanks): 

a. Manufacturer’s name 

b. Model/serial number 

c. Design service pressure 

d. Direction of flow 

e. Capacity 

f. Fuel type (i.e., label “gaseous hydrogen”) 

3. Fuel Tank Certification and Recertification (e.g., similar to requirements of 49 CFR 571.304 

for CNG tanks but applied to gaseous hydrogen tanks) 

a. Design Certification Test 

b. Maintenance Personnel Certification2

c. Periodic retesting and labeling (per Pamphlet C6)3

d. Record of last defects visual inspection 

 

2 “CSA America is the only known standards development organization in the U.S. that provides testing and certification for qualified 

compressed natural gas (CNG) cylinder inspections and maintains a National Registry of Certified inspectors. To qualify for a new certification, 

or to renew an existing certification, candidates must successfully pass a certification exam. To maintain their status without re-examination, 

certified CNG Inspectors must perform and submit reports on 10 vehicle or 50 cylinder inspections per year.” 

3 Compressed Gas Association, Inc., Pamphlet C-6: Standards for Visual Inspection of Compressed Gas Cylinders, 1984.

9 
4. Pressure Relief Devices (PRDs) installed on fuel tanks in direct contact with fuel (e.g., 

similar to requirements of 49 CFR 571.304 for CNG tanks but applied to gaseous hydrogen 

tanks) 

5. Fueling Connection 

a. Grounding and bonding requirements 

b. Dust cap 

c. Labeling the fueling compartment or fueling door with “gaseous hydrogen,” service 

pressure, and installer or company name because all the information may not fit on the 

fueling compartment door; therefore, some of the information for Item 5 may be placed 

on the back panel of the fueling compartment so that it can be seen when the fueling door 

is opened. 

d. Support for fueling connector 

6. Fuel Tank System Installation 

a. Protection and shielding from road hazards 

b. Mounted to minimize damage from collision 

c. Mounting racks are secured 

d. Clearance from road to storage tank container 

e. Shielded against heat sources 

f. Fuel system components electrically bonded and grounded (specific for hydrogen) 

7. Venting System 

a. Hydrogen venting or purging does not vent to hazardous location (i.e., not to engine 

compartment or wheel well) 

b. Vent piping system shall be metallic 

c. Hydrogen does not vent or purge to restrict PRD safety devices 

d. Venting system contains protective cap or cover 

e. Secured at outer end 

f. Venting of enclosed spaces where leaked gaseous fuel might collect 

g. Not blocked by ice, snow, or debris 

8. Piping and valves 

a. Provide automatic shutoff valve for fuel tanks in response to system fault. 

b. Provide manual shutoff valve. 

9. Installation of Fuel Pressure Gauge 

10 
10. Wiring 

a. High voltage labeling is properly labeled and color coded. 

b. Do not route through passenger compartment. 

c. Ground fault detection system shall be provided. 

d. Live components behind cover/enclosure labeled with high-voltage symbols. 

e. Connectors are not loose, broken, cracked, or otherwise defective. 

11. Post Accident Precautions – Inspection and replacement following an accident (e.g., similar 

to requirements of 49 CFR 571.304 S7.4(g) for CNG tanks but applied to gaseous hydrogen 

tanks) 

12. Gas Leak Detection System (e.g., regulation should require a hydrogen leak detection 

system) 

13. Shutoff Valve - Turning off main on/off switch isolates fuel to storage tank 

14. Driver Awareness Training Program – Suggest vehicle operator attend hydrogen hazard 

awareness training and compressed gas hazards. 

15. Activities – The use of cellular phones during fueling in the fueling area should be 

prohibited. 

11 
7. CONSIDERING CHANGES TO FMCSRs FOR 

LIQUID HYDROGEN 

To properly regulate liquid hydrogen fueled commercial vehicles, specific regulations should be 

considered for liquid hydrogen. The following areas should be considered for inclusion into 

updated regulations: 

1. Vehicle Labeling 

a. Requirement for “diamond” type labeling of commercial vehicle as a liquid hydrogen 

vehicle 

- Label (consistent with Society of Automotive Engineer [SAE] J2578, Recommended 

Practice for Hydrogen Vehicles) 

- Location (suggested in tow locations on opposing sides of vehicle cab) 

- Size (suggested readable at 50 ft) 

2. Fuel Components and Tank Labeling (similar to the requirements of 49 CFR 571.304 

requirements but applied to liquid hydrogen tanks) 

a. Fuel type (i.e., liquid hydrogen) 

b. Manufacturer’s name 

c. Model number/serial number 

d. Design service pressure 

e. Direction of flow 

3. Fuel Tank Certification and Recertification (similar to the requirements of SAE standard 

J2343 for liquefied natural gas (LNG) tanks but applied to liquid hydrogen tanks) 

a. Design Certification Test 

b. Periodic retesting and labeling 

4. Pressure Relief Valves (PRVs) installed on fuel tanks 

5. Fueling Connection 

a. Grounding and bonding requirements 

b. Dust cap 

c. Labeling the fueling compartment or fueling door “liquid hydrogen” with service 

pressure, and installer or company 

6. Fuel Tank System Installation 

a. Protection and shielding 

b. Mounted to minimize damage from collision 

c. Mounting racks are secured 

12 
d. Clearance from road to storage tank container 

e. Shielded against heat sources 

f. Fuel system components electrically bonded and grounded (specific to hydrogen) 

g. Fuel system components insulated, vapor sealed, and protected from casual contact 

7. Venting System 

a. Venting diffuser output to less than 20% of the lower flammable limit 

b. Hydrogen venting or purging does not vent to hazardous location (i.e., not to engine 

compartment or wheel well) 

c. Vent piping system shall be metallic 

d. Hydrogen does not vent or purge to restrict PRD safety devices 

e. Venting of enclosed spaces where leaked gaseous fuel might collect 

f. Venting system contains protective cap or cover 

g. Secured at outer end 

h. Not blocked by ice, snow, or debris 

8. Piping and valves 

a. Provide automatic shutoff valve for fuel tanks 

b. Provide manual shutoff valve 

9. Installation of fuel liquid level gauge 

10. Wiring 

a. High voltage labeling is properly labeled and color coded 

b. Do not route through passenger compartment 

c. Ground fault detection system shall be provided 

d. Live components behind cover/enclosure labeled with high voltage symbols 

e. Connectors are not loose, broken, cracked, or otherwise defective 

11. Post Accident Precautions – Inspection and replacement (similar to requirements of 49 CFR 

571.304 S7.4g for CNG tanks but applied to liquid hydrogen tanks) 

12. Leak Detection 

13. Shutoff Valve - Turning off main on/off switch isolates fuel to storage tank. 

14. Driver Awareness Training Program – Suggest vehicle operator attend hydrogen hazard 

awareness training including a module on cryogenic hazards. 

15. Activities – The use of cellular phones during fueling in the fueling area should be 

prohibited. 

13 
8. NORTH AMERICAN STANDARD (NAS) 

INSPECTION PROCEDURES 

The North American Standard (NAS) Inspection program has five levels of inspections, 

established by CVSA: 

• Level I: Detailed driver and vehicle inspection 

• Level II: Driver inspection and walk-around vehicle inspection 

• Level III: Driver only inspection 

• Level IV: Special one-time inspections of a particular item 

• Level V: Vehicle only inspection without a driver present (typically conducted at a 

carrier facility/terminal) 

• Level VI: Enhanced Level I inspection for radioactive shipments (includes additional 

checks for vehicles carrying radioactive hazardous materials). 

Table 1 below shows the various inspection levels and what is typically performed. 

Three types of inspections are generally implemented by inspection oversight agencies: 

• Annual 

• Trip 

• “Random” roadside 

Certainly, everything that has been specified for consideration in sections 10 and 11 apply to the 

more thorough, comprehensive annual inspections, which generally occur at the 

owner/operator’s facilities or at an inspection facility. The comprehensive annual inspections 

would make use of a checklist similar to the CHP checklists for LNG and CNG, except that these 

would be for liquid hydrogen and compressed hydrogen. Only certain parts of sections 10 and 11 

apply to both the trip and “random” roadside inspections. 

The trip and “random” roadside inspections may be discussed together at the same time because 

whatever the driver can do, the inspector can, and vice verse. Those parts of sections 10 and 11 

that would apply to both the trip and “random” roadside inspections should include the 

following: 

• Verifying that the annual inspection was performed, 

• Ensuring that the appropriate labels are affixed properly for hydrogen, 

• Checking for certification/recertification of the hydrogen storage tanks, 

• Observing for any visible damage to the hydrogen storage tanks, 

• Checking for properly functioning leak detection system as well as for leaks, and 

• Confirming that the operator (if present) has had hydrogen awareness training. 

14 
Table 1. Inspection Levels 

Inspection Item 

Level I 

Level II 

Level III 

Level IV 

Level V 

Level VI 

Driver’s License ✔ ✔ ✔ ✔ 

Medical Examiner’s Certificate and Waiver ✔ ✔ ✔ ✔ 

Alcohol and Drugs ✔ ✔ ✔ ✔ 

Driver’s Log (HOS and Duty Status) ✔ ✔ ✔ ✔ 

Seatbelt System ✔ ✔ ✔ ✔ ✔ 

Vehicle Inspection Report ✔ ✔ ✔ ✔ ✔ 

Brake System ✔ ✔ ✔ ✔ 

Coupling Devices ✔ ✔ ✔ ✔ 

Exhaust System ✔ ✔ ✔ ✔ 

Frame ✔ ✔ ✔ ✔ 

Fuel System * ✔ ✔ ✔ ✔ 

Lights/Lamps ✔ ✔ ✔ ✔ 

Safe Loading of Cargo ✔ ✔ ✔ ✔ 

Steering Mechanism ✔ ✔ ✔ ✔ 

Suspension ✔ ✔ ✔ ✔ 

Tires ✔ ✔ ✔ ✔ 

Wheels, Rims, Hubs ✔ ✔ ✔ ✔ 

Van and Open Top Trailer Bodies ✔ ✔ ✔ ✔ 

Windshield Wipers ✔ ✔ ✔ ✔ 

Emergency Exits (buses) ✔ ✔ ✔ ✔ 

Hazardous Materials Requirements ✔ ✔ ✔ ✔ 

One Time Special Inspection of an Item ✔ 

Radiological Requirements ✔ 

* Highly pertinent to hydrogen-fueled vehicles. 

8.1 BASIS FOR CONSIDERING CHANGES TO NAS INSPECTION PROCEDURES 

For commercial vehicles that use hydrogen as an alternative fuel, it is clear that procedures for 

examining the integrity of the fuel system will need to be modified. Specifically, the fuel system 

inspection requirements for Levels I, II, V, and VI need to be modified for commercial vehicles 

that use hydrogen as an alternative fuel. The basis for identifying changes to the inspection 

procedures are based on the current practices developed by the California Highway Patrol for 

inspection of natural gas vehicles (see attached inspection checklists for CNG and LNG in 

appendix A). 

15 
9. CONSIDERING CHANGES TO INSPECTION 

PROCEDURES FOR GASEOUS HYDROGEN 

Since commercial vehicle inspectors are enforcing regulations, the inspection procedures for 

commercial vehicles that use hydrogen as an alternative fuel should also be considered for 

modification. It is important to note that not all changes to the FMCSRs specified for 

consideration in section 6.0 have associated inspection procedures. In particular, FMCSRs 

associated with wiring have not been included in the consideration of changes to inspection 

procedures that are listed below. Wiring is not included because it is not listed as a safety-critical 

inspection item. Based on the review, Level I and Level V procedures should be considered for 

modification, including the following inspection areas of commercial vehicles that use hydrogen 

as an alternative fuel: 

1. Verify and Inspect Vehicle Labeling 

a. Requirement for labeling commercial vehicle as a gaseous hydrogen fueled vehicle: 

- Label (consistent with Society of Automotive Engineer [SAE] J2578, Recommended 

Practice for Hydrogen Vehicles) 

- Location (suggested in tow locations on opposing sides of vehicle cab) 

- Size (suggested readable at 50 ft) 

2. Verify and Inspect Fuel Components and Tank Labeling (e.g., similar to requirements of 49 

CFR 571.304 for compressed natural gas (CNG) tanks but applied to gaseous hydrogen 

tanks): 

a. Manufacturer’s name 

b. Model/serial number 

c. Design service pressure 

d. Direction of flow 

e. Capacity 

f. Fuel type (i.e., “gaseous hydrogen”) 

3. Verify and Inspect Fuel Tank Certification and Recertification (e.g., similar to requirements 

of 49 CFR 571.304 for CNG tanks but applied to gaseous hydrogen tanks) 

a. Design Certification Test 

b. Periodic retesting and labeling 

c. Record of last visual inspection 

4. Verify and Inspect Pressure Relief Devices (PRDs) installed on fuel tanks (e.g., similar to 

requirements of 49 CFR 571.304 for CNG tanks but applied to gaseous hydrogen tanks) 

16 
5. Verify and Inspect Fuel Connection 

a. Grounding and bonding requirements 

b. Dust cap 

c. Labeling the fueling compartment or fueling door with “gaseous hydrogen,” service 

pressure, and installer or company name 

d. Support for fueling connector 

6. Verify and Inspect Fuel Tank System Installation 

a. Protection and shielding from road hazards 

b. Mounted to minimize damage from collision 

c. Mounting racks are secured 

d. Clearance from road to storage tank container 

e. Shielded against heat sources 

f. Fuel system components electrically bonded and grounded (specific for hydrogen) 

7. Verify and Inspect Venting System 

a. Venting diffuser output to less than 20% of the lower flammable limit 

b. Hydrogen venting or purging does not vent to hazardous location (i.e., not to engine 

compartment or wheel well) 

c. Vent piping system shall be metallic 

d. Hydrogen does not vent or purge to restrict PRD safety devices 

e. Venting system contains protective cap or cover 

f. Secured at outer end 

g. Venting of enclosed spaces where leaked gaseous fuel might collect 

h. Not blocked by ice, snow, or debris 

8. Verify and Inspect piping and valves integrity 

a. Provide automatic shutoff valve for fuel tanks in response to system fault 

b. Provide manual shutoff valve 

9. Verify and Inspect Installation of Fuel Pressure Gauge 

10. Verify and Inspect Post Accident Precautions – Inspection and replacement following an 

accident (e.g., similar to the requirements of 49 CFR 571.304 S7.4(g) for CNG tanks but 

applied to gaseous hydrogen tanks) 

11. Verify and Inspect Gas Leak Detection System (e.g., regulation should require a hydrogen 

leak detection system and that it should be functioning properly) 

17 
12. Verify and Inspect main on/off switch isolates fuel to storage tank. 

13. Verify operator has attended hazard training. (Note: This does not apply to Level V 

inspections where the operator is not present.) 

The consideration of changes to procedures specified in this section pertain to the required 

commercial vehicle inspections. Safety procedures, training, and guidance should be provided to 

vehicle inspectors or enforcement officers with respect to hydrogen system safety. For example, 

inspectors or enforcement officers should not be smoking or using radios or cell phones while 

detecting for leaks or checking any lines or connections that carry high-pressure gas (usually 

identifiable by stainless steel tubing). 

18 
10.CONSIDERING CHANGES TO INSPECTION PROCEDURES 

FOR LIQUID HYDROGEN 

Since commercial vehicle inspectors are enforcing regulations, the inspection procedures for 

commercial vehicles that use liquid hydrogen as an alternative fuel should also be considered for 

modification. It is important to note that not all changes to the FMCSRs specified for 

consideration in section 7.0 have associated inspection procedures. In particular, FMCSRs 

associated with wiring have not been included in the consideration of changes to inspection 

procedures that are listed below. Wiring is not included because it is not listed as a safety-critical 

inspection item. Based on the review, Level I and Level V procedures should be considered for 

modification, including the following inspection areas of commercial vehicles that use hydrogen 

as an alternative fuel: 

1. Verify Vehicle Labeling 

a. Requirement for “diamond” type labeling of commercial vehicle as a liquid hydrogen 

vehicle 

- Label (consistent with Society of Automotive Engineer [SAE] J2578, Recommended 

Practice for Hydrogen Vehicles) 

- Location (suggested in tow locations on opposing sides of vehicle cab) 

- Size (suggested to be readable at 50 ft) 

2. Verify Fuel Components and Tank Labeling (similar to the requirements of 49 CFR 571.304 

for CNG tanks but applied to liquid hydrogen tanks) 

a. Fuel type (i.e., liquid hydrogen) 

b. Manufacturer’s name 

c. Model number/serial number 

d. Design service pressure 

e. Direction of flow 

3. Verify Fuel Tank Certification and Recertification (similar to the requirements of SAE 

standard J2343)4 for LNG tanks but applied to liquid hydrogen tanks 

a. Design Certification Test 

b. Periodic retesting and labeling 

4. Verify Pressure Relief Valves (PRVs) installed on fuel tanks 

 

4 Society of Automotive Engineers [SAE J2343], J2343 – Recommended Practices for LNG Powered Heavy-Duty Trucks, 

January 1997.

19 
5. Verify and Inspect Fueling Connection 

a. Grounding and bonding requirements 

b. Dust cap 

c. Labeling the fueling compartment or fueling door “liquid hydrogen” with service 

pressure and installer or company 

6. Verify and Inspect Fuel Tank System Installation 

a. Protection and shielding 

b. Mounted to minimize damage from collision 

c. Mounting racks are secured 

d. Clearance from road to storage tank container 

e. Shielded against heat sources 

f. Fuel system components electrically bonded and grounded (specific to hydrogen) 

g. Fuel system components insulated, vapor sealed, and protected from casual contact 

7. Verify and Inspect Venting System 

a. Venting diffuser output to less than 20% of the lower flammable limit 

b. Hydrogen venting or purging does not vent to hazardous location (i.e., not to engine 

compartment or wheel well) 

c. Vent piping system shall be metallic 

d. Hydrogen does not vent or purge to restrict PRD safety devices 

e. Venting of enclosed spaces where leaked gaseous fuel might collect 

f. Venting system contains protective cap or cover 

g. Secured at outer end 

h. Not blocked by ice, snow, or debris 

8. Verify and Inspect Piping and valves 

a. Provide automatic shutoff valve for fuel tanks 

b. Provide manual shutoff valve 

9. Verify Installation of fuel liquid level gauge 

10. Verify Post Accident Precautions – Inspection and Replacement (similar to requirements of 

49 CFR 571.304 for CNG tanks but applied to liquid hydrogen tanks) 

11. Verify and Inspect Leak Detection System 

20 
12. Verify Shutoff Valve - Turning off main on/off switch isolates fuel to storage tank 

13. Verify Driver Awareness Training Program – Suggest all vehicle operators attend hydrogen 

hazard awareness training including cryogenic hazard. (Note: This does not apply to Level V 

inspections where the operator is not present.) 

The consideration of changes to procedures specified in this section pertain to the required 

commercial vehicle inspections. Safety procedures, training, and guidance should be provided to 

vehicle inspectors or enforcement officers with respect to hydrogen system safety. For example, 

inspectors or enforcement officers should not be smoking, using radios or cell phones while 

detecting for leaks or observing any lines or connections that carry high-pressure gas (usually 

identifiable by stainless steel tubing). 

21 
11.CONSIDERING CHANGES TO NAS 

OUT OF SERVICE ORDERS 

In addition to modifying NAS inspection procedures for commercial vehicles that use hydrogen 

as an alternative fuel, changes should be considered to the NAS Out of Service Criteria (dated 

January 1, 2004). The Out of Service Criteria provides guidance to commercial vehicle 

inspectors for placing commercial vehicles out of service as a result of inspection findings. Just 

as a leak in a diesel fuel system serves as a basis for placing a commercial vehicle out of service, 

likewise, a leak in a system using hydrogen as an alternative fuel on a commercial vehicle should 

serve as a basis for placing such a commercial vehicle out of service. For commercial vehicles 

that use hydrogen as an alternative fuel, the following out of service criteria should be considered 

for addition to the existing NAS criteria: 

• Any fuel system leak detected by an onboard leak detection system 

• Any fuel system leak detected by an audible noise, or detected by a hand-held hydrogen 

detector and confirmed by a “soap bubble test”5

• Any fuel system leak that vaporizes in the air 

• Any such commercial vehicle operating without a hydrogen leak detection system or 

operating with a defective hydrogen leak detection system 

 

5 Hand held hydrogen detectors indicate the presence of hydrogen, but can not generally confirm the existence, or pinpoint the location of, 

an active leak. The general procedure for leak checking is as follows: (1) Use a hand held hydrogen detector to sample the air in the vicinity of 

all major hydrogen bearing components (tanks, valves, pressure regulators), especially near connections and piping joints, where leaks are most 

likely to occur, and (2) if the hand held detector senses a hydrogen concentration greater than 25% of the lower flammable limit, conduct a 

“soap bubble test” in that area to confirm/pinpoint the leak. For the soap bubble test, pour or spray a non-ammonia, non-corrosive soap solution 

onto each connection/joint in the area where hydrogen was detected and observe for several minutes. If small bubbles appear and multiply in the 

soap solution, it is an indication that hydrogen gas is leaking through the joint. 

22 
12.SUMMARY/CONCLUSION 

Based on a review of existing Federal Motor Carrier Safety Regulations and the North American 

Standard Inspection Procedures, additional regulations and inspections procedures are needed to 

accommodate commercial vehicles that use hydrogen as an alternative fuel. Specifically, the 

FMCSRs need to be updated to accommodate gaseous and cryogenic liquefied hydrogen fuel. 

The regulation updates need to consider the hazards associated with gaseous and liquid hydrogen 

including the properties of hydrogen, operating pressures, cryogenic hazards, safety devices, and 

hydrogen hazard awareness training. The inspection procedures for these vehicles also need to be 

updated accordingly. As the result of an inspection, any hydrogen leak that is detected should 

serve as an additional criterion for placing a commercial vehicle out of service. 

23 
APPENDIX A: California Highway Patrol Inspection Procedures 

for Compressed Natural Gas and Liquefied Natural Gas 

Figure 1. California Highway Patrol Inspection Checklist—Form CHP 353A 

24 
Figure 2. California Highway Patrol Inspection Checklist—Form CHP 354 

25 
REFERENCES 

Compressed Gas Association, Inc., Pamphlet C-6: Standards for Visual Inspection of 

Compressed Gas Cylinders, 1984 

Federal Motor Carrier Safety Administration (FMCSA), Guidelines for use of Hydrogen Fuel in 

Commercial Vehicles, 2007 

National Fire Protection Association, NFPA 52 – Vehicle Fuel Systems Code – 2006 Edition. 

Society of Automotive Engineers (SAE), J2343 – Recommended Practices for LNG Powered 

Heavy-Duty Trucks, January 1997 

Society of Automotive Engineers (SAE), J2578 - Recommended Practice for Hydrogen 

Vehicles, December 2004 

26