Billing Code: 4910-60-P
DEPARTMENT OF TRANSPORTATION
Pipeline and Hazardous Materials Safety Administration
[Docket No. PHMSA-2023-0108, (Notice No. 2023-13)]
Hazardous Materials: Request for Feedback on De Minimis Quantities of Explosives
AGENCY: Pipeline and Hazardous Materials Safety Administration (PHMSA), Department of
Transportation (DOT).
ACTION: Notice; request for information.
SUMMARY: PHMSA is publishing this notice to solicit information from hazardous materials
(HAZMAT) shippers pertaining to what small quantities or low concentrations of explosives
they offer for transport appear to present a low risk to life, property, and the environment.
DATES: Interested parties are invited to submit comments on or before [INSERT DATE 90
DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. Comments
received after that date will be considered to the extent possible.
ADDRESSES: You may submit comments identified by the Docket Number PHMSA-20230108 by any of the following methods:
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Federal eRulemaking Portal: http://www.regulations.gov. Follow the instructions for
submitting comments.

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Fax: 1-202-493-2251.

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Mail: Docket Management System; U.S. Department of Transportation, West Building,
Ground Floor, Room W12–140, Routing Symbol M–30, 1200 New Jersey Avenue SE,
Washington, D.C. 20590.

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Hand Delivery: Docket Management System; Room W12-140 on the ground floor of the
West Building, 1200 New Jersey Avenue SE, Washington, D.C. 20590, between 9 a.m.
and 5 p.m., Monday through Friday, except Federal holidays.

Instructions: All submissions must include the agency name and Docket Number
[PHMSA-2023-0108] for this notice. To avoid duplication, please use only one of these four
methods. All comments received will be posted without change to the Federal Docket
Management System (FDMS) and will include any personal information you provide.
Docket: For access to the dockets to read background documents or comments received,
go to http://www.regulations.gov or DOT’s Docket Operations Office (see ADDRESSES).
Privacy Act: In accordance with 5 U.S.C. 553(c), DOT solicits comments from the
public. DOT posts these comments, without edit, including any personal information the
commenter provides, to http://www.regulations.gov, as described in the system of records notice
(DOT/ALL–14 FDMS), which can be reviewed at http://www.dot.gov/privacy.
Confidential Business Information (CBI): CBI is commercial or financial information that
is both customarily and actually treated as private by its owner. Under the Freedom of
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public disclosure. If your comments
responsive to this notice contain commercial or financial information that is customarily treated
as private, that you actually treat as private, and that is relevant or responsive to this notice, it is
important that you clearly designate the submitted comments as “CBI.” Please mark each page of
your submission containing CBI as “PROPIN.” Submissions containing CBI should be sent to
Michael Klem, Pipeline and Hazardous Materials Safety Administration, U.S. Department of
Transportation, 1200 New Jersey Avenue SE, Washington, D.C. 20590-0001. Any commentary
PHMSA receives that is not specifically designated as CBI will be placed in the public docket for
this notice.
FOR FURTHER INFORMATION CONTACT: Andrew Leyder, Office of Hazardous
Materials Safety, Research, Development & Technology, Pipeline and Hazardous Materials
Safety Administration, U.S. Department of Transportation, 1200 New Jersey Avenue SE,
Washington, D.C. 20590-0001, by phone at 202-360-0664, or by e-mail at
andrew.leyder@dot.gov.

SUPPLEMENTARY INFORMATION:
I.

Purpose
PHMSA is publishing this notice to HAZMAT shippers to determine, based on their

experience, what small quantities or low concentrations of explosives they offer for transport that
appear to present a low risk (e.g., negligible severity, remote probability, etc.) to life, property,
and the environment. The information will be used to define the focus of a research project
investigating the risk of small and/or de minimis quantities of explosive substances and in
selecting test samples for PHMSA research and development Contract# 693JK322C00003.
II.

Background
HAZMAT is comprised of substances or materials capable of posing an unreasonable risk

to life, property, and the environment when transported in commerce. PHMSA issues the
Hazardous Materials Regulations (HMR), contained in title 49 of the Code of Federal
Regulations (CFR) parts 171–180, for the safe and secure transportation of HAZMAT. When
packaged in inner and outer packagings that do not exceed small threshold quantities, specific
classes of HAZMAT can be offered for transport without being subject to many or all of the
HMR requirements. Exceptions for small quantities of HAZMAT in transport include the
following:
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Small quantities for highway and rail within the U.S. (49 CFR 173.4).

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Excepted quantities (49 CFR 173.4a).

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De minimis exceptions (49 CFR 173.4b)
Currently there are no small quantity exceptions for Class 1 explosives. Rather, the HMR

requires that any change in the formulation, design, or process that alters any of the properties of
a Class 1 explosive means it is now considered a “new explosive” and must be examined,
classed, and approved for transport. Obtaining a U.S. DOT PHMSA explosives (EX) approval
requires significant commitments of time, effort, and financial resources by the prospective
shipper, examining agent, and PHMSA. Establishing a small quantity and/or de minimis

exception for explosives presenting a low hazard in transport would reduce the time, effort, and
financial investments required by all affected parties in order to authorize its transport, while
maintaining the safety of the transportation system.
Although there are no small quantity exceptions for Class 1 explosives with a general
scope that might apply to broad categories of small quantity or low concentration explosives,
there are a few narrowly defined exceptions that authorize the transport of specific explosive
substances that have been desensitized to impact, friction, and/or flame initiation, such as:
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UN2555, Nitrocellulose with water [with not less than 25% water, by mass], 4.1, II
(≤75% explosives content, 1.1D when undiluted); UN3357, Nitroglycerin mixture,
desensitized, liquid, n.o.s. with not more than 30% nitroglycerin, by mass, 3, II (30%
explosives content, forbidden from transport when undiluted); or UN1204, Nitroglycerin
solution in alcohol [with not more than 1% nitroglycerin], 3, II (1% explosives content,
forbidden from transport when undiluted).
o Each can be offered for transport in inner packagings containing up to 30 grams
per 49 CFR 173.4 or 173.4a or 1 gram per 49 CFR 173.4b.

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UN1571, Barium azide, wetted [with not less than 50% water], by mass, 4.1, I (≤50%
explosives content, 1.1A when undiluted); UN1322, Dinitroresorcinol, wetted [with not
less than 15% water, by mass], 4.1, I (≤85% explosives content, 1.1D when undiluted);
UN3366, Trinitrotoluene (TNT), wetted, [with not less than 10 % water by mass], 4.1, I
(≤90% explosives content, 1.1D when undiluted); or UN3370, Urea nitrate, wetted, [with
not less than 10% water by mass], 4.1, I (≤90% explosives content, 1.1D when
undiluted).
o Each can be offered for transport in inner packagings containing up to 30 grams
per 49 CFR 173.4.
Therefore, although the small quantity exceptions authorize the transport of specific and

narrowly defined desensitized explosives, the current quantity exceptions do not have allowances

for broader categories of small quantity or low concentration explosives defined by lower
concentration without individual testing/examination, nor allowances that define when a diluted
explosive might be excepted from the HMR requirements.
III.

PHMSA’s Exceptions for Desensitized Explosives
There are currently no small quantity or de minimis exceptions for Class 1 explosive

substances or articles in the United States. However, the following exceptions permit the
transport of various desensitized explosives that have been excluded from Class 1 (summarized
by the following bullets; refer to the regulatory text for the full requirements and allowances):
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49 CFR 173.4 (Small quantities for highway and rail within the U.S.) authorizes inner
packagings containing up to 30 g of authorized solids or 30 mL of authorized liquids in
an outer packaging not exceeding a gross mass of 29 kg.

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49 CFR 173.4a (Excepted quantities) authorizes inner packagings containing up to 30 g
of authorized solids or 30 mL of authorized liquids in an outer packaging not exceeding a
net mass 300 g or 300 mL for PG I solids or liquids; 500 g or 500 mL for solids or liquids
of PG II; and 1 kg or 1 L for PG III solids or liquids/gases.

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49 CFR 173.4b (De minimis exceptions) authorizes inner packagings containing up to 1 g
of authorized solids or 1 mL of authorized liquids with an aggregate quantity of
HAZMAT not exceeding 100 g or 100 mL in an outer packaging not exceeding a gross
mass of 29 kg.

IV.

Request for Feedback
We are interested in understanding what small quantities or low concentrations of

explosives are offered for transport that appear to present a low risk to life, property, and the
environment. For this inquiry, an explosive meets the definition of 49 CFR 173.50(a) and United
Nations Recommendations on the Transport of Dangerous Goods section 2.1.1 and 2.1.1.3. The
phrase “low risk to life, property, and the environment” means a risk comprised of a negligible
severity and a remote probability (as defined in MIL-STD-882E, “Department of Defense

Standard Practice, System Safety”, 11 May 2012) for the worst-case scenario related to
transportation, including preparation for transport, storage, and/or handling incidental to
movement. From MIL-STD-882E, negligible severity and remote probability are defined as:
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Negligible severity - Could result in one or more of the following: injury or
occupational illness not resulting in a lost work day, minimal environmental
impact (air/water/solid waste pollutant emissions, inadvertent hazardous releases,
or adverse change upon resources/ecosystems), or monetary loss less than $100K.

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Remote probability - Unlikely, but possible for an incident to occur in the life of
the item.

The information will be used to define the focus of a research project investigating the
risk of small and/or de minimis quantities of explosive substances, and in selecting test samples
for PHMSA Research & Development Contract# 693JK322C00003. PHMSA requests comment
on the following questions:
1. Which of the following items do you encounter that a) are to be offered for transport,
and b) contain small quantities and/or low concentrations of explosives? Examples
could include, but are not limited to: analytical standards, canine training aids,
residues in packaging (bags, boxes, drums, etc.), residues on tooling or equipment,
contaminated lubricants, residues in piping, residues from processing (wipes, swabs,
paper/plastic/textile sheets or covers, absorbent pads, filter media, etc.), residues from
handling (gloves, aprons, masks, respirator cartridges, clothing, etc.), manufacturing
residues, floor sweepings, residues in solvent or water washes, contaminated soil,
and/or other.
2. How frequently does your facility offer small quantities or low concentrations of
explosives as a HAZMAT shipper that appear to present a low risk to life, property,
and the environment?

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Never [skip to question 8]

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Rarely [continue to next question]

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Yearly [continue to next question]

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Monthly [continue to next question]

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Weekly [continue to next question]

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Daily [continue to next question]

3. Please provide responses to the following sub-questions (3.1 to 3.10) for the top five
examples of small quantities or low concentrations of explosives encountered by your
facility that present a low risk to life, property, and the environment. Please focus on
examples at your facility that: a) are most frequently encountered; b) represent the
greatest mass/volume; c) have the highest net explosives weight; d) have the highest
explosives concentration; and/or e) have the greatest amount of explosives.
3.1.

What is the composition of the HAZMAT (constituents, concentration,
quantity, etc.)?

3.2.

What is the packaging configuration of the HAZMAT (inner, intermediate,
and outer packagings)?

3.3.

What is the average net explosives weight of the inner package (in grams)?

3.4.

What is the average net explosives weight of the outer package (in grams)?

3.5.

What is this HAZMAT's UN identification number?

3.6.

On average, how many packages of this HAZMAT are in one shipment?

3.7.

On average, how many shipments of this HAZMAT are made in one year?

3.8.

What mode(s) of transport is/are utilized for these shipments (e.g., motor
vehicle, passenger or cargo-only rail/aircraft, vessel, etc.)?

3.9.

Where is this HAZMAT typically shipped? Specify all that apply: another
facility for further manufacturing; customer or end user; recycling
(reclamation, reuse/use, etc.); hazardous waste facility for

chemical/thermal/biological/physical treatment; hazardous waste facility
for disposal (dumpsite, landfill, etc.); public landfill; and/or other.
3.10. Is the HAZMAT offered for transport internationally or domestically in
intrastate (within the same state) or interstate (between states) commerce?
3.11. What type of approval is currently being utilized to offer the HAZMAT for
shipment? (e.g., EX-approval, Special Permit, or Competent Authority).
3.12. What tests were performed to characterize the hazard of the HAZMAT?
3.13. Are you willing to share more detailed information (e.g., the test report,
recommended classification, and EX-approval) with Safety Management
Services, Inc. (SMS) of West Jordan, Utah? SMS is willing to sign nondisclosure agreements to protect proprietary information; further details can
be securely transmitted to them.
4. As applicable, please list up to five examples of small quantities and/or low
concentrations of explosives presenting more than a low risk to life, property, and the
environment.
5. All materials containing explosives, including small quantities or dilute
concentrations, require a PHMSA approval prior to transport; it can take up to 180
days to examine, classify, and approve a regulated explosives-containing material for
transport. What impact does waiting for PHMSA approval of your small quantities
and/or dilute explosives have upon your facility, in your efforts to comply with the
requirements of other regulatory agencies?
6. What threshold quantity and/or concentration of explosives, if any, presents a low risk
to life, property, and the environment, and should, in your opinion, be considered for
exception from regulation by PHMSA?
7. What is the technical basis for your opinion (e.g., testing, experience, data, etc.)?

8. Why, in your opinion, should a threshold quantity and/or concentration of explosives
not be considered for exception from regulation by PHMSA?
Your efforts to comment on the above questions are appreciated; your responses will be
used to better inform decisions in determining small quantity and/or de minimis exceptions for
explosive substances and in selecting test samples for Contract# 693JK322C00003.
Issued in Washington, D.C.
Yolanda Y. Braxton,
Director,
Operations System Division,
Office of Hazardous Materials Safety,
Pipeline and Hazardous Materials Safety Administration.
[FR Doc. 2024-14175 Filed: 6/27/2024 8:45 am; Publication Date: 6/28/2024]