United States
Environmental Protection
Agency
Office of Solid Waste
and Emergency Response
(5104)
EPA550-F-97-002d
December 1997
www.epa.gov
EXPLOSION HAZARD FROM
AMMONIUM NITRATE
The Environmental Protection Agency (EPA) is issuing this Alert as part of its ongoing effort to
protect human health and the environment. EPA is striving to learn the causes and contributing
factors associated with chemical accidents and to prevent their recurrence. Major chemical
accidents cannot be prevented solely through command and control regulatory requirements but
by understanding the fundamental root causes, widely disseminating the lessons learned, and
integrating these lessons learned into safe operations. EPA will publish Alerts to increase
awareness of possible hazards. It is important that facilities, SERCs, LEPCs, emergency responders
and others review this information and take appropriate steps to minimize risk.
PROBLEM
ACCIDENTS
Ammonium nitrate primarily is
used as a fertilizer; it also is used
widely with additives as a
blasting agent. Millions of tons of this
chemical are produced annually
throughout the world and handled
without incident. According to scientific
literature, ammonium nitrate is a strong
oxidizer and a relatively stable explosive.
For the purpose of transportation,
ammonium nitrate with less than 0.2
percent combustible substances and
ammonium nitrate fertilizers are
classified by the U.S. Department of
Transportation as oxidizers. Ammonium
nitrate with more than 0.2 percent
combustible substances is classified as an
explosive. Ammonium nitrate can be
exploded under certain conditions.
These must include added energy (heat,
shock), especially under conditions of
confinement or presence of
contaminants. Although ammonium
nitrate generally is used safely and
normally is stable and unlikely to
explode accidentally, accidental
explosions of ammonium nitrate have
resulted in loss of lives and destruction
of property. These accidents rarely occur,
but when they do, they have high
impacts. Many of the safe handling
procedures were developed after
learning from these accidents.
In a 1994 accident, ammonium nitrate
solution exploded during a
manufacturing process, causing a
number of deaths and injuries. In this
process, ammonia and nitric acid were
reacted in a neutralizer vessel to produce
83 percent ammonium nitrate solution
for use in fertilizer. At the time of the
accident, the neutralizer contained
approximately 164,000 pounds of
ammonium nitrate. During a procedure
to shut down the process, compressed
air was applied to the nitric acid line into
the neutralizer, followed by pressurized
steam at 200 pounds per square inch
gauge (psig) and temperatures up to
430°F. After the steam had passed
through the nitric acid line for several
hours, the ammonium nitrate exploded
in the neutralizer. EPA believes localized
areas of the ammonium nitrate solution
were heated to high temperatures by the
steam. The compressed air and steam
created bubbles in the solution. The
solution was highly acidic and was
contaminated by chlorides. EPA believes
the acidic conditions, bubbles, localized
high temperatures, and chloride
contamination contributed to the
explosion.
Chemical Emergency Preparedness and Prevention Office
i Printed on recycled paper
-------
Explosion Hazard from Ammonium Nitrate
December 1997
Another explosion occurred in 1989, during the
manufacture of ammonium nitrate by a high
temperature process. In this case, upset
conditions allowed prolonged exposure of
ammonium nitrate to temperatures up to 500°F
under high pressure and low pH (acidic).
Other past accidental explosions of ammonium
nitrate have included some of the most
destructive on record. Several of these, including
two in Germany in 1921, occurred during
attempts to break up large piles of solidified or
caked ammonium nitrate-ammonium sulfate
mixtures using a blasting explosive. The blasting
initiated explosions in the ammonium nitrate-
ammonium sulfate mixtures. Other large
explosions were triggered by fires involving
ammonium nitrate in confined spaces, including
the 1947 explosion of two cargo ships. A fire in
the hold, involving ammonium nitrate fertilizer
coated with wax and stored in paper bags,
caused the explosion of the first ship; the
ammonium nitrate in the second ship exploded
some time later, apparently as a result of a fire
caused by the first explosion. As a result of such
accidents and subsequent studies of the
properties of ammonium nitrate, caked
ammonium nitrate no longer is broken up with
blasting agents, and wax coatings are no longer
used for ammonium nitrate fertilizer.
Explosions of ammonium nitrate, involving
relatively small quantities, have occurred during
the preparation of nitrous oxide. In these cases
(e.g., an explosion in 1977), the explosions of
ammonium nitrate occurred as a result of
excessively high temperatures and confinement
during processing.
Two explosions of ammonium nitrate solutions
that occurred during processing at ordnance
plants during the Second World War were
believed to be caused by the explosion of a small
amount of ammonium nitrate in a blocked pipe,
which then initiated the explosion of a larger
quantity of solution.
HAZARD AWARENESS
A
mmonium nitrate, in solid or molten
form or in solution, is a stable compound
and generally is difficult to explode.
Ammonium nitrate may explode, however,
when exposed to strong shock or to high
temperature under confinement. In a large
quantity of ammonium nitrate, localized areas
of high temperature may be sufficiently confined
by the total quantity to initiate an explosion. The
explosion of a small quantity of ammonium
nitrate in a confined space (e.g., a pipe) may
initiate the explosion of larger quantities (e.g.,
in an associated vessel).
Contaminants may increase the explosion
hazard of ammonium nitrate. Organic materials
generally will make ammonium nitrate
explosions more energetic. Ammonium nitrate
may be sensitized by certain inorganic
contaminants, including chlorides and some
metals, such as chromium, copper, cobalt, and
nickel. As ammonium nitrate solution becomes
more acidic, its stability decreases, and it may
be more likely to explode.
Low density areas, such as bubbles, in molten
ammonium nitrate or solutions, also may
increase the possibility of an explosion and
enhance the propagation of an explosion.
Ammonium nitrate by itself does not burn, but
in contact with other combustible materials, it
increases the fire hazard. It can support and
intensify a fire even in the absence of air. Fires
involving ammonium nitrate can release toxic
nitrogen oxides and ammonia. A fire involving
ammonium nitrate in an enclosed space could
lead to an explosion. Closed containers may
rupture violently when heated.
PROCESS SAFETY AREAS
FOR HAZARD REDUCTION
Facilities should be aware of the hazards of
ammonium nitrate and ensure that the
conditions that may lead to an explosion
are not present. Actions that may help to prevent
explosions include:
+ Avoid heating ammonium nitrate in a
confined space (e.g., processes involving
ammonium nitrate should be designed to
avoid this possibility).
-------
Explosion Hazard from Ammonium Nitrate
December 1997
+ Avoid localized heating of ammonium
nitrate, potentially leading to development
of high temperature areas.
4- Ensure that ammonium nitrate is not ex-
posed to strong shock waves from explo-
sives.
+ Avoid contamination of ammonium nitrate
with combustible materials or organic
substances such as oils and waxes.
4- Avoid contamination of ammonium nitrate
with inorganic materials that may contrib-
ute to its sensitivity to explosion, including
chlorides and some metals, such as chro-
mium, copper, cobalt, and nickel.
4 Maintain the pH of ammonium nitrate
solutions within the safe operating range of
the process. In particular, avoid low pH
(acidic) conditions.
INFORMATION RESOURCES
The National Fire Protection Association (NFPA)
includes information on ammonium nitrate in its
publication NFPA 49— Hazardous Chemicals
Data, 1994. This publication provides guidance on
hazardous chemicals to emergency personnel and
others.
National Fire Protection Association
1 Batterymarch Park
PO. Box 9101
Quincy, MA 02269-9101
Phone: (617)770-3000
Web site: http://www.nfpa.org
The National Safety Council has a data sheet titled
"Ammonium Nitrate Fertilizer, Data Sheet 1-699,
Rev. 91" that discusses the health hazards, properties,
and precautions for safe storage and handling of
ammonium nitrate fertilizer.
National Safety Council
1121 Spring Lake Drive
Itasca, IL 60143-3201
Phone: (630) 285-1121
Web site: http://www.nsc.org
Some references that contain
information about the hazards of
ammonium nitrate and methods of
minimizing these hazards are listed below.
Regulations applicable to the manufacture of or
processes involving ammonium nitrate, and
codes and standards that may be relevant, are
also listed.
General References
The following references and organizations provide
information on ammonium nitrate and its hazards.
Sax's Dangerous Properties of Industrial
Materials, Ninth Edition. New York: Van
Nostrand Reinhold (1996).
Kirk-Othmer Encyclopedia of Chemical
Technology, Fourth Edition, Volume 2. New
York: John Wiley & Sons (1992).
The Fertilizer Institute possesses information on
various fertilizer products, including ammonium
nitrate, and their uses.
The Fertilizer Institute
501 Second Street, NE
Washington, DC 20002
Phone: (202) 675-8250
Statutes and Regulations
Section 112(r) of the Clean Air Act focuses on
prevention of chemical accidents. It imposes on
facilities with regulated substances or other extremely
hazardous substances a general duty to prevent and
mitigate accidental releases. This general duty would
apply to hazards associated with ammonium nitrate.
Accident prevention activities include identifying
hazards and operating a safe facility.
-------
Explosion Hazard from Ammonium Nitrate
December 1997
EPAs Risk Management Program (RMP) Rule (40
CFR 68) is intended to prevent and mitigate
accidental releases of listed toxic and flammable
substances. Requirements under the RMP rule
include development of a hazard assessment, a
prevention program, and an emergency response
program. While ammonium nitrate is not a 112(r)
listed substance, chemicals used in the production of
ammonium nitrate are included on the 112(r) list.
Certain processes using ammonium nitrate may also
involve listed substances.
The Department of Transportation (DOT) regulates
transportation of ammonium nitrate under its
Hazardous Materials Regulations. Ammonium
nitrate is listed in DOT's Hazardous Materials Table
(49 CFR 172.101).
Department of Transportation
Phone: (202) 366-5580 - Public Information
Web site: http://www.dot.gov
The Occupational Safety and Health Administration
(OSHA) regulates the manufacture, keeping, having,
storage, sale, transportation, and use of explosives
and Hasting agents under its Occupational Safety
and Health Standards for explosives and Hasting
agents (29 CFR 1910.109). Blasting agents are
frequently formulated with ammonium nitrate.
OSHA's Process Safety Management Standard
establishes procedures intended to protect employees
by preventing or minimizing the consequences of
chemical accidents involving highly hazardous
chemicals (29 CFR 1910.119). Although ammonium
nitrate is not covered by the PSM standard, the
production or use of ammonium nitrate may involve
listed chemicals in excess of thresholds. Manufacture
of explosives, which may involve ammonium nitrate,
also is covered by the PSM standard.
The Bureau of Alcohol, Tobacco, and Firearms of the
Department of the Treasury regulates the importation,
manufacture, distribution, and storage of explosive
materials (27 CFR 55), including blasting agents and
other explosives containing ammonium nitrate.
Bureau of Alcohol, Tobacco, and Firearms
Phone: (202) 927-7777
Web site: http://atf.treas.gov
Codes and Standards
NFPA has developed a code for storage of ammonium
nitrate, including mixtures containing 60 percent or
more by weight of ammonium nitrate, and a code for
explosives that would apply to blasting agents and
explosives containing ammonium nitrate. These
codes, which may be adopted into law at the state or
local level, are:
NFPA 490 — Storage of Ammonium Nitrate,
1993, and
NFPA 495 — Explosive Materials Code, 1996.
Accident Investigation Report
EPA investigated the ammonium nitrate
explosion that occurred in 1994 and developed
the following report:
United States Environmental Protection Agency,
Region 7, Emergency Response and Removal
Branch, Kansas City, KS, Chemical Accident
Investigation Report — Terra Industries, Inc.,
Nitrogen Fertilizer Facility, Fort Neal, Iowa
Occupational Safety and Health Administration
Phone: (202) 219-8151 - Public Information
Web site: http://www.osha.gov
-------
Explosion Hazard from Ammonium Nitrate
December 1997
FOR MORE INFORMATION...
CONTACT THE EMERGENCY PLANNING AND
COMMUNITY RIGHT-TO-KNOW HOTLINE
(800) 424-9346 OR (703) 412-9810
TDD (800) 553-7672
MONDAY-FRIDAY, 9 AM TO 6 PM, EASTERN TIME
VISIT THE CEPPO HOME PAGE ON THE WORLD
WIDE WEB AT:
http://www.epa.gov/swercepp/
NOTICE
The statements in this document are intended solely as guidance. This document does not substitute for EPA's or other
agency regulations, nor is it a regulation itself. Site-specific application of the guidance may vary depending on process
activities, and may not apply to a given situation. EPA may revoke, modify, or suspend this guidance in the future, as
appropriate.
------- |