Haz-mat Response

Of tigers and kittens and what we learned

Of tigers and kittens and what we learned

A recent video that circulated on the Internet depicted a full-grown tiger leaping high into the air to fetch a slab of meat. The tiger’s meal was thrown over a 20-foot-high fence that kept all of the tigers in their cage. To see a 700-pound tiger propel itself into the air from a standing start and grab the meat with its fangs several feet higher than the fence was at once spectacular and unsettling. In a split-second maneuver, this majestic cat provided a realization never before seen and never before realized. In a word, the capability of what this feline could do was “underestimated.”

As a hazardous materials (hazmat) response instructor, I have used this short video to illustrate how responders can also underestimate the power and capability of some hazardous materials. When the lid comes off a haz-mat container, or when the tiger gets out of the cage, it can hurt or harm anything or anyone in its path-and sometimes in unexpected ways. A healthy respect for all hazmat needs to be cultivated if we want to go home after every call. Conversely, not all hazmats may be as dangerous as we think, and we may severely overestimate their chemical and physical characteristics. In other words, sometimes we are really dealing with a hazmat kitten and may not even realize it. To prove this point, I will share an eye-opening incident that proved to be monumental in my own hazmat response development.

Hazmat Terms

To fully understand hazmat response, a study of both chemical and physical terms is a must. Not only are the definitions of the important terms paramount, but examples must be examined along with contrasts between common hazmats. At about this point, most students’ eyes gloss over, but I have found that by looking at real-life incidents and their results, a competent instructor can keep them interested and in the game. Since a chemical compound’s boiling point (BP) is the temperature at which a liquid readily changes into a vapor, it is important to show that the BPs of some of the hazmat tigers include anhydrous ammonia, chlorine, and propane (Table 1). These three hazmats are frequently released in our country and cause harm because they are gases in our ambient environment. And when they are released, they commonly produce visible vapor clouds because of their low temperatures. In my experience, a visible vapor cloud is a “bad day in the neighborhood” because gases and vapors are the things that combust, burn, or explode, and being airborne is what people and animals are injured by through inhalation.

Additionally, if a material has a low boiling point it will also have a low flash point (FP). Flash point is the temperature at which a liquid will evolve enough vapor content so that if an ignition source is presented, the vapors will temporarily ignite. Of the examples above, anhydrous ammonia and propane are flammable gases and technically do not have flash points because they exist as gases below our ambient temperatures. Some common liquids with flash points include acetone, cyclohexylamine, and ethanol (Table 1). These materials rarely present as vapor clouds because they are usually the same temperature as the environment and sometimes will not present a flammable hazard so a liquid spill is quite often a “good day in the neighborhood.”

Table 1.

Gases at Room Temperature


Boiling Point

Flash Point

Vapor Pressure

Flammable Range

Chemical Formula

Anhydrous Ammonia



110 psi @ 68F






113 psi @ 77F






110 psi @75F



Liquids at Room Temperature


Boiling Point

Flash Point

Vapor Pressure

Flammable Range

Chemical Formula




180 mm/Hg @68F






11 mm/Hg @68F






43 mm/Hg @68F



Urea Formaldehyde Concentrate


Boiling Point

Flash Point

Vapor Pressure

Flammable Range

Chemical Formula


Approximately 200°F




Mixture of urea, formaldehyde, methanol, and water

Note: 760 millimeters of mercury (mm/Hg) equals 14.7 pounds per square inch (psi) equals 1 atmosphere (atm.) equals 1 Torr.

Still another term to look at is vapor pressure (VP). Vapor pressure is defined as the pressure a gas or vapor that emanates from a liquid exerts on the walls and the top of a container at equilibrium. VP is temperature dependent, so as the temperature increases, the vapor pressure of any material will also correspondingly increase. Vapor pressure curves for most materials are readily available through research (Table 2).

Table 2. Vapor pressure is temperature dependent.


At Boiling Point

At 0°F

At 68°F

At 100°F

At 120°F

Anhydrous Ammonia

0 psig (-28°F)

15 psig

110 psig

197 psig

271 psig


0 psig (-29°F)

14 psig

80 psig

140 psig

187 psig


0 psig (-44°F)

24 psig

98 psig

172 psig

214 psig

The important point here is with the relationship of all of the above: If a material has a low BP, it will also have a low FP, and it will, correspondingly, have a high VP at any given temperature. (Also remember the opposite is true!)(Table 3). This premise is vital for all responders to remember because it should be included in all risk management considerations and is a key consideration in all hazmat strategic and tactical decision making. The case study that follows will prove my point.

Table 3.

For any chemical compound, if it has a low boiling point (BP), it will have a correspondingly low flash point (FP) and a correspondingly high vapor pressure (VP).

Low BP -> Low FP -> High VP

The inverse is also true: For any chemical compound, if it has a high boiling point (BP), it will have a correspondingly high flash point (FP) and a correspondingly low vapor pressure (VP).

High BP -> High FP -> Low VP

Case Study

On an extremely cold morning in February, early in my career, an emergency call was received from a fertilizer company at which an overpressurization of a liquid storage tank occurred. The temperature was -5°F, and the pressure relief device to an atmospheric tank that held a fertilizer solution had frozen shut because of the weather. At approximately 0500 hours, a truck driver had begun to pump a solution of urea formaldehyde into the 6,000-gallon storage tank from an outside connection (photo 2). After he got the system going, he walked across the street to have a cup of coffee, but little did he know that the solution he pumped into the tank was raising the internal pressure because there was no way for the displaced air to travel because the pressure relief device was frozen shut. In short order, the weak spot in the system resulted when a welded seam near the top of the storage tank ruptured because of the internal pressure.

At the time of the rupture, two company workers happened to be inside the same room as the tank. The rupture caused the stressed concrete roof of this room to shift slightly and consequently jam the exit doors to the room. The room had normally been heated to 40°F to prevent the solution from freezing, and at this point the heat had escaped because of the shifted roof. The emergency call included two trapped workers who had been exposed to chemical vapors.

Engine 5 arrived at approximately 0530 hours and gathered information from workers on scene. A hazmat alarm was struck, and the team arrived at approximately 0600 hours and began their own assessment. The truck driver had his coffee break cut short when he noticed that the red lights and emergency efforts were centered on his off-loading activities.

The hazmat research effort concerning the fertilizer solution revealed that it was a water-based material with up to 60 percent formaldehyde and up to 25 percent urea dissolved into the solution. A small amount of methanol also was mentioned as an ingredient and that may be used as a stabilizer agent because of formaldehyde’s tendency to polymerize. This material was called UF-85 to represent its components. Formaldehyde, with a formula of HCHO, is a gas at ambient temperatures that is flammable, and it is also a toxic material that is listed as a carcinogen. It is known for its pungent odor. Urea is a nitrogen-based solid material that is dissolved into the solution to serve as a potent fertilizer. Since all of these additives are water-based, they needed to be stored in a heated room to prevent freezing. UF-85 has a flash point of 174°F (Table 1).

Shortly after the research results were considered, it was decided to have two responders in Level A suits cut through one of the room’s concrete block walls to make an exit for the trapped workers. (As I was one of the responders in Level A, the difficulty and risk of this task still resounds in my mind to this day.) While we donned the chemical suits inside a city bus that was brought to the scene, as soon as we exited the bus the suits stiffened up because of the extreme cold. As we neared the wall we were to breach, our suit visors had frosted over on the inside because of the condensation of our own body temperature and the cold outside. Additionally, as we climbed the scaffolding that was provided on site, which we used as a platform to conduct our task, we could hardly see what we were doing. (We frequently used our fingernails to scrape the frost from the inside of the visors of our suits.)

Running the rotary saw with a concrete blade was even more precarious, all while standing on plywood and with no side rails to prevent falls. Fortunately, we made several cuts along some of the mortar seams until we ran out of air and had to exit the area. To finish the task, a team of firefighters in structural fire protective clothing (SFPC) and self-contained breathing apparatus (SCBA) broke through the remaining concrete blocks with sledgehammers. Shortly after breaching the wall, we removed the workers from the room (photo 1).

Successful Response

In retrospect, this response was successful in that two workers were rescued from a compromised structure that also included a hazmat exposure. While neither worker had any residual affects because of the chemical odor, their main complaint was exposure to the extreme cold. What we learned, however, was that the chemical exposure risk was extremely low because of the low environmental temperature. As a result of a -5°F ambient temperature, the material would not physically produce enough vapor to cause a problem in terms of acute chemical exposure, both through inhalation and skin absorption and in terms of producing a flammable atmosphere. In essence, the cold weather suppressed the solution’s ability to become airborne because its vapor pressure was almost nothing.

This emergency made us rethink how we analyzed hazmat incidents and that not every incident was an automatic Level A situation. In the early days of hazmat response, the common hazmat team battle cry was “Level A all the way!” Our experience on this extremely cold day indicated that future events needed to be looked at holistically and that Level A is required on few incidents. That is, in addition to researching the released material’s hazards, we also needed to consider the situation at hand, the logistics of what was needed for mitigation, the risk management concerns, and the environmental conditions on scene. In other words, we subjected ourselves to increased risk because of the limitations of Level A suits in extreme cold; working on an unguarded, elevated platform; and operating power equipment, all with very limited vision. Essentially, we encountered a kitten and we overestimated the hazards of UF-85 that day.

Clarion UX