This month our example is Anhydrous
Ammonia, which has a chemical formula of NH3.
Ammonia is readily dissolved in water to form Ammonium
Hydroxide a corrosive, alkaline solution at high
concentrations. Ammonia is listed under more than one UN
# (United Nations Number) by the US Department of
Transportation: UN 2672 (between 12% and 44% aqueous
solution), UN 2073 (>44% aqueous solution), UN 1005
(anhydrous gas or >50% aqueous solution).
At room temperature, anhydrous ammonia is a
colorless, highly irritating gas with a pungent,
suffocating odor. It is lighter than air and flammable,
with difficulty, at high concentrations and
temperatures. It is easily compressed and forms a clear,
colorless liquid under pressure. Anhydrous ammonia is
hygroscopic. Ammonia dissolves readily in water to form
ammonium hydroxide, an alkaline solution. The
concentration of aqueous ammonia solutions for household
use is typically 5% to 10% (weight:volume), but
solutions for commercial use may be 25% (weight:volume)
or more and are corrosive. Aqueous ammonia is commonly
stored in steel drums. Anhydrous ammonia is stored and
shipped in pressurized containers, fitted with
pressure-relief safety devices, and bears the label
“Nonflammable Compressed Gas”. However, Anhydrous
Ammonia can form flammable mixtures with air at certain
concentrations and therefore should be treated as
odor threshold is sufficiently low to acutely provide
adequate warning of its presence (odor threshold = 5
ppm; OSHA PEL = 50 ppm). However, ammonia causes
olfactory fatigue or adaptation, making its presence
difficult to detect when exposure is prolonged.
Anhydrous ammonia is lighter than air at ambient
temperature and will therefore rise (will not settle in
low-lying areas); however, vapors from liquefied gas are
initially heavier than air (because of the cold
temperature) and may spread along the ground.
Asphyxiation may occur in poorly ventilated or enclosed
exposed to the same levels of ammonia vapor as adults
may receive larger dose because they have greater lung
surface area:body weight ratios and increased minute
volumes:weight ratios. In addition, they may be exposed
to higher levels than adults in the same location
because of their short stature and the higher levels of
ammonia vapor found nearer to the ground.
It is a health hazard because of its
toxicity and it is flammable forming mixtures with air
that are flammable or explosive.
is manufactured by reacting hydrogen with nitrogen.
About 80% of the ammonia produced is used in
fertilizers. It is also used as a refrigerant gas, and
in the manufacture of plastics, explosives, pesticides,
and other chemicals, as a corrosion inhibitor, in the
purification of water supplies, as a component of
household cleaners, in the pulp and paper, metallurgy,
rubber, food and beverage, textile and leather
industries, and in the manufacture of pharmaceuticals.
Ammonia is also produced naturally from decomposition of
organic matter and under unusual conditions, can reach
include Ammonia gas; Ammonia, anhydrous; Anhydrous
ammonia; Aromatic Ammonia, Vaporole; Nitro-Sil; and
Spirit of Hartshorn.
NIOSH IDLH (immediately dangerous to
life or health) = 300 ppm.
AIHA ERPG-2 (maximum
airborne concentration below which it is believed that
nearly all persons could be exposed for up to 1 hour
without experiencing or developing irreversible or other
serious health effects or symptoms that could impair
their abilities to take protective action) = 200 ppm.
Ammonia reacts with strong oxidizers, acids,
halogens (including chlorine bleach), and salts of
silver, zinc, copper, and other heavy metals. It is
corrosive to copper and galvanized surfaces.
Exposure: Anhydrous ammonia reacts with moisture in
the mucous membranes to produce an alkaline solution
(ammonium hydroxide). Exposure to ammonia gas or
ammonium hydroxide can result in corrosive injury to the
mucous membranes of the eyes, lungs, and
gastrointestinal tract and to the skin due to the
alkaline pH and the hygroscopic nature of ammonia.
Exposure: Repeated exposure to ammonia may cause
chronic irritation of the respiratory tract. Chronic
cough, asthma and lung fibrosis have been reported.
Chronic irritation of the eye membranes and dermatitis
have also been reported.
Anhydrous Ammonia gas has a boiling
point of -28°F and a melting point of -108°F. Its
molecular weight is 17, and has a relative vapor density
is 0.6 (compared to air). It will rise but because it is
normally stored or shipped as a compressed liquified gas
when it is released it will rapidly cool and because of
this initial low temperature it will seek low areas. The
lower Explosive Limit (LEL) is 15%; the Upper Explosive
Limit (UEL) is 28%.
- Keep in a cool, dry, dark location in a tightly
sealed container or cylinder. Keep away from
incompatible materials, ignition sources and untrained
individuals. Secure and label area. Protect
containers/cylinders from physical damage.
- All chemicals should be considered hazardous.
Avoid direct physical contact. Use appropriate, approved
safety equipment. Untrained individuals should not
handle this chemical or its container. Handling should
occur in a chemical fume hood.
- Wear appropriate protective gloves, clothing and
- Wear positive pressure self-contained breathing
spills or leaks - Keep material out of water sources
and sewers. Attempt to stop leak if without undue
personnel hazard. Use water spray to knock-down vapors.
Vapor knockdown water is corrosive or toxic and should
be diked for containment. Land spill: Dig a pit, pond,
lagoon, holding area to contain liquid or solid
material. Dike surface flow using soil, sand bags,
foamed polyurethane, or foamed concrete. Absorb bulk
liquid with fly ash or cement powder. Neutralize with
vinegar or other dilute acid. Water spill: Neutralize
with dilute acid. Use mechanical dredges or lifts to
remove immobilized masses of pollutants and
- Reactive only under extreme conditions. Reacts
vigorously with oxidizing materials.
- Reacts violently or produces explosive products
with fluorine, chlorine, bromine and iodine and bromine
pentafluoride and chlorine trifluoride May react
violently with boron halides, ethylene oxide
(polymerization), perchlorates and strong oxidizing
agents (chromyl chloride, chromium trioxide, chromic
acid, nitric acid, hydrogen peroxide, chlorates,
fluorine, nitrogen oxide, liquid oxygen).
Decomposition - Shock-sensitive compounds are formed
with mercury, silver and gold oxides.
Charges - Liquid ammonia can cause ignition if
sprayed in a tank containing air.
Health related information
Exposure effects -
in blood pressure and pulse have been reported. An
altered mental status (coma) may be seen, but is not
characteristic unless hypoxemia occurs. Seizures may
occur with extensive absorption. Decreased egg
production has occurred in experimental animals. Ammonia
crosses the ovine placental barrier.
- Nausea and vomiting occur frequently following
ingestion. Swelling of the lips, mouth, and larynx, and
oral or esophageal burns may occur if concentrated
ammonia solutions are ingested.
- Vapors are extremely irritating and corrosive.
- Concentrated ammonia may produce liquifaction
necrosis and deep penetrating burns.
- A small quantity in the eye will cause permanent
damage. Also frostbite. Vapor causes a burning sensation
and irritation. Cold vapor may cause frostbite.
- Seek medical assistance.
- Move victim to fresh air. Apply artificial
respiration if victim is not breathing. Do not use
mouth-to-mouth method if victim ingested or inhaled the
substance; induce artificial respiration with the aid of
a pocket mask equipped with a one-way valve or other
proper respiratory medical device. Administer oxygen if
breathing is difficult. Effects may be delayed.
- Remove contaminated clothing and wash exposed area
thoroughly with soap and water. A physician should
examine the area if irritation or pain persists.
- In case of contact with liquefied gas, thaw
frosted parts with lukewarm water immediately flush skin
with running water for at least 20 minutes.
In using the PEAC application we
access information for the chemical by first locating
Anhydrous Ammonia in the database. The following figures
show the screens displayed for chemical properties,
Figure 1 for the PEAC-WMD for Windows application
and Figure 2-5 for the PEAC‑WMD for the Pocket PC
- Using the Lookup By: Name for Anhydrous Ammonia using
the PEAC-WMD for Windows application
Review of the information displayed
in the chemical properties screen whether in Figure 2
(above) or Figures 3-5 (below), show chemical properties
values discussed earlier at the top of this discussion.
As you can see, the published toxicity values, e.g.,
IDLH, ERPGs (Emergency Response Protection Guidelines)
published by American Industrial Hygiene Association,
and the TEELs (Temporary Emergency Exposure Limits)
published by Department of Energy are provided. We will
use the IDLH as the Level of Concern when we develop the
PAD a little later.
Figure 2 – Selecting Anhydrous
Ammonia using the PEAC-WMD for Pocket PC
Figure 3 – The top portion of the
Chemical Properties Data Display Screen
Figure 4 – The middle portion of
the Chemical Properties Data Display Screen
Figure 5– The bottom portion of
the Chemical Properties Data Display Screen
The PEAC-WMD application provides
more than just the Chemical Properties for the
identified material, the Chemical Properties are
just the default information screen displayed, by
clicking (if running the Windows version, see Figure 6)
or tapping (if running the Pocket PC version, see Figure
7) on the drop-down box where Chemical Properties
is displayed on the screen, the user is provided with a
list of other databases that provide information for the
selected chemical (Anhydrous Ammonia in our current
example). So the search is done once, and the user is
indexed into the different databases easily and quickly.
Figure 6 – Accessing other
databases from the PEAC-WMD for Windows
Figure 7 – Accessing other
databases from the PEAC-WMD for Pocket PC
A quick review or sampling of the
type of information available in each of these screens
is now provided. First is access to Respirators
Recommendations, these are primarily taken from the
NIOSH Pocket Guide and provide the user with different
types of respirators for increasing concentrations. A
sample of the information is provided in Figure 8.
Likewise the Chemical Protective Clothing (CPC)
database can be accessed by clicking on either the
All Chemical Protective Clothing or the
Available Chemical Protective Clothing selection
as shown in Figure 9. The All Chemical Protective
Clothing displays all the CPC entries in the
PEAC‑WMD database for the selected chemical vs. the
Available Chemical Protective Clothing displays
just those CPC entries that match the manufacturers the
user has previously identified as the products the
response organization typically keeps in inventory.
Figure 8 – Respirator
Recommendations for Anhydrous Ammonia
Figure 9 – Chemical Protective
Clothing for Anhydrous Ammonia
The IC (Incident Commander) will
typically utilize more than a single resource for
developing a response plan but sometimes the information
in other resources will use a different name for the
same substance. Clicking on the Synonyms
selection will provide a quick list of other names
the substance may be referenced by in other resources as
shown in Figure 10. To further assist the responder in
initiating the best response plan, PEAC‑WMD also
provides the generic guidelines found in the ‘orange
pages’ of the DOT Emergency Response Guidebook (ERG).
These are categorized into different types of procedures
depending on the incident and the problem to be
mitigated. An example for Spill or Leak Response
is shown in Figure 11. >
|Figure 10 – Synonyms
||Figure 11 – ERG Spill or
Leak Response |
A benefit of using the PEAC tool is
assistance in the development of an evacuation zone for
those chemicals that produce a toxic vapor cloud.
Depending on the incident Anhydrous Ammonia can be
released from a container as either a vapor or a liquid.
As with all of our examples, AristaTek creates a
scenario for a spill or release of the specific
chemical, and then we work through the development of a
PAD (Protective Action Distance) to demonstrate how the
PEAC system works.
Anhydrous Ammonia is a common
chemical used primarily for agriculture purposes
although it is also used for refrigeration so it can be
found in numerous settings. A relatively recent event
involving Anhydrous Ammonia occurred in Minot, ND in
January of 2002. A number of railcars derailed close to
the city late at night releasing hundreds of thousands
of gallon of Anhydrous Ammonia. There was only one
fatality and numerous long-term health effects that are
currently in the process of litigation. Considering the
extreme potential of the hazard the Minot community was
fortunate since the consequences could have been much
more severe, although certainly those with the long-term
health effects probably don’t share the same
For our hypothetical scenario using
Anhydrous Ammonia as the spilled chemical we’ll set the
location to be on the Southwest outskirts of Omaha, NE
where the Union Pacific Railroad passes beneath I-80.
The time is 4:00 AM on June 15th and a
railcar of Anhydrous Ammonia on the UP Railroad has been
derailed and breached, dumping its contents. The
temperature is about 75°F, the winds are about 2 mph,
and it’s a clear night (no clouds). There are
residential and commercial areas nearby and light
traffic on the nearby highways.
As seen at the top of the data
display screens, there is a yellow icon displayed; this
is the PEAC icon for notifying the user that a
Protective Action Distance can be calculated. Clicking
or tapping on the PAD icon will display a screen as
shown in Figure 12. Following through the screens, we
provide information on the Meteorology, Container Size,
and Type of Release (Source). The last screen displays
the PAD based on the provided information. If you decide
to follow along on this example, remember to change the
location to Omaha and the time to 4:00 AM, June
It’s Omaha in June and the
temperature about 75°, light wind is set for 2
mph, clear sky so we’ll set cloud cover to 0%, and
the terrain is Urban/Forest since it’s an urban
We have selected from our list
of container sizes the Railcar selection.
This provides us with a default size that should
get us pretty close to the actual size.
Since the scenario calls for a
loss of contents, we’ve selected a Large
Rupture as the Source type of release.
Figure 12 – Calculating a PAD using the
By pressing the right arrow at the
top of the screen, the PEAC system will display a screen
as shown in Figure 13. This just reminds the user that
the PEAC-WMD tool has calculated a PAD greater than 7
miles and to use the results with caution. This is
primarily because wind speed and terrain can change
significantly over long distances.
Figure 13 – Warning Message to use the
results with caution because things vary of long
Once the warning message has been
acknowledged by clicking or tapping on [OK], the
PAD calculated is displayed as shown in Figure 14. This
calculates a PAD (Protective Action Distance)
based on the default Level of Concern the IDLH of
300 ppm. This evacuation or standoff distance is based
on the toxicity of Anhydrous Ammonia, not its
flammability. Since it is flammable at certain
concentrations, care needs to be given to ignition
sources in the immediate vicinity of the release.
Figure 14 – Default PAD for Anhydrous
Ammonia-Using the IDLH of 300 ppm
Clicking or tapping on the pop up
list for the Level of Concern a list of published
toxicity values for Anhydrous Ammonia is displayed.
Clicking or tapping on the ERPG-2 value of 200 ppm
(Figure 15) and will allow the PEAC tool to recalculate
a PAD for the 200 ppm concentration Level of
Concern. In our example the PAD for the 200 ppm
concentration is displayed (Figure 16).
Figure 15 – Selecting another Level of
Figure 16 – PAD for ERPG-2 (200
Portions of this discussion were
adapted from the WEB site supported by the Hardy
Research Group, Department of Chemistry, The University
of Akron: http://ull.chemistry.uakron.edu/. Additional
information was also adapted from the Agency for Toxic
Substances and Disease Registry (ATSDR) Web site for
Medical Management Guidelines at: http://www.atsdr.cdc.gov/.