by Kem Russell

The majority of am monia refrigeration systems are well built, – lesson well maintained, and operated by people who know what they’re doing. IIAR has several Standards established to help in design, construction, maintenance and inspection of ammonia refrigeration systems and all of these factors usually result in no more than incidental releases from systems. Although rare, a system can have a potentially large release, or an actually significant event.

Because larger releases are uncommon it puts a burden on us, each facility and company, to be prepared. In the event I’m about to describe, no one was injured, either in the facility or in the surrounding community, but it was a BIG wake-up call to not only the facility, but to many groups and individuals in the community.

The incident happened around 7 am on a cold morning. Light wind, totally overcast sky, and temperature in the low 20’s. I was on my way to meet with the refrigeration manager at a large cold storage facility when I got an alert on my phone from the Office of Emergency Management. When I got to the cold storage facility, the refrigeration manager wasn’t there to meet me, which was unusual. I called his cell phone, and he answered saying that he had gone to pick up his grandmother and would be back shortly. I didn’t know at the time that his grandmother – along with several hundred other people in the small community – were in the process of being evacuated because of an ammonia release.

At the release site, the refrigeration operators had been in the control room, which was located in the machine room, when they heard a loud hissing noise. Looking into the machine room they saw next to one of the screw compressors a large white plume of ammonia shooting toward the ceiling. The machine room was quickly filling with ammonia vapor. Not having any personal protective equipment that might have (falsely) let them approach the release, they used the control system to shut down all compressors, and quickly left.

The facility had no response capabilities, and realized they needed help fast. 911 was called, and since it was early, many people had not yet left for work so the local Fire Department, made entirely of volunteers, quickly responded. (Something to think about, who will be responding to help you?). Since the facility that was in the middle of the release was right down the street from the Fire Department, the Fire Department didn’t have to go anywhere. The Fire Chief realized he also needed additional help because none of his fireman were trained to respond to an ammonia release.

Appropriate calls were quickly made by the facility experiencing the release, as well as the Fire Chief. And as other emergency agencies arrived, Unified Command was quickly established and it was determined that an evacuation of the area surrounding the facility was necessary since it could take close to an hour before ammonia hazmat-capable responders arrived.

Now, here are some lessons learned in just the first few minutes of this event. Recall the outdoor conditions: cold temperatures, light wind, low cloud cover. The ammonia vapor leaving the machine room did not immediately rise and disperse in the atmosphere, but slowly began spreading out downwind of the release point. Ammonia doesn’t always go up and away. Ambient conditions make a difference.

Remember too, ammonia vapor is lighter than air, and will move fairly rapidly. In this particular case the ammonia could be smelled just outside of the Fire Department within a short time. With the ammonia spreading, it was quickly determined that the small community business center, as well as the surrounding homes for more than a mile around the release should be evacuated. Another lesson here is, how do you quickly notify all of the surrounding businesses and homes of an ammonia release?

In this case the Office of Emergency Management and the county had in place a system to call all phones. Land lines in certain districts, as well as cell phones were called. Two challenges came to light. One, the computerized message could only be 90 characters long, so careful thought had to go into the messages, which left many in the public wondering exactly what was happening. Two, the cell phone coverage area is 360 degrees around cell towers, so many people were notified that were not within the incident area, which also caused some confusion.

People in the area were instructed to go to one of the local schools well outside of the release area. Now let’s go back to the refrigeration manager I was going to meet. He realized his grandmother was in the affected area. He was concerned and tried to call his grandmother, but couldn’t get a hold of her so he decide to go to her house.

Here is another lesson learned. Depending on the area of an emergency, and how large that emergency is, there may not, at least initially, be enough emergency personnel to respond. In this case there wasn’t. So, even though hundreds of people were self-evacuating from the area and the area was supposed to be closed to entry, there were many roads into the area that could not be manned. People outside the area were very concerned about their family members inside the affected area. Several of those people drove around the unmanned road blocks. When the refrigeration manager reached his grandmother’s house, she wasn’t there. Where was she?

Unbeknownst to the refrigeration manager, one of his grandmother’s neighbors had taken her to the school. Here another lesson was learned. One of the emergency messages sent out was that the school was in “lockdown”. Now if you had one of your family members in a school that said it was in “lock-down”, what comes to mind? One of the first thoughts might be “active shooter”. Many people had that very thought and were very interested in getting their family member(s) out of there. (If you don’t know, when a school is in “lockdown,” no one gets in or out.) The emergency message might have caused much less concern if it had stated that the school is a “shelter-in-place” location. A few well-chosen words can make a big difference.

Even with some confusion as the incident unfolded, no one in the business area or surrounding homes was injured or physically affected by the release. The emotional aftermath, at least for a short period following the incident, was another story. The school did an outstanding job accommodating the surrounding community in this emergency even though it really wasn’t a “lock-down,” which the school often practiced. The school also knew and had practiced the redirecting of students coming into the area from other schools. Smart.

Let’s look at the incident from the facility point of view. The refrigeration operators and many others that worked at the facility safely evacuated or sheltered-in-place. The facility had not really spent much effort in training employees about evacuation or shelterin-place, which they are now correcting. The facility also learned that the machine room ventilation system did not function properly, and neither did the machine ammonia detector. There was also no emergency shutdown located outside of the machine room, nor any ventilation system control. There were no drawings of the refrigeration system that could have helped in narrowing down the release point.

The facility did learn they were prepared to make the required notifications by calling 911, NRC, State, and LEPC. In that regard the attendance of some of the company personnel at a past LEPC meeting where plastic cards with emergency contact information were handed out proved very beneficial.

Now let’s look briefly at what was learned from the interaction of the facility with emergency responders. Due to the fact that the refrigeration operators (wisely) quickly left the machine room, they could not help much as the emergency responders began deciding what to do. The power company was called to shut off power, but the event was over before they could assemble their team at the facility. Many ammonia events are like that. They happen quickly, and everyone needs to respond in an appropriate and timely manner. In this case having everyone remain at a safe distance was a good decision.

About 1.5 hours or so into the release, it could be clearly seen that the release rate had greatly reduced, and the white vapor leaving the machine room was almost nonexistent. Since the refrigeration operators could not point to what was going on in the machine room, the hazmat team had suited up, Level-A, and with ammonia detector in hand were preparing to enter the machine room to close the king valve.

People can argue about whether to close the king valve or not. An understanding of the possible effects of this action should come from the facility personnel who should have sufficient knowledge of their system, as well as other information that can help the emergency responders make a reasonable plan. The best, not just good, not just better, but the best outcome occurs when facility and emergency responders work together.

In this case closing the king valve would have had no effect on the amount of ammonia release. In this incident the release was coming from a high pressure liquid line that was dedicated for liquid injection oil cooling of the screw compressors. This was a separate liquid supply line coming from the high pressure receiver. The release was stopped when a valve in the high pressure liquid injection supply line was closed just upstream of the valve assembly that had failed.

We can learn a lot from past incidents. This incident actually went pretty well. However, the one big lesson that needs further learning is that facilities and emergency responders must work together. They must communicate and practice often enough to be prepared for an emergency. They must develop a working relationship so that when help is needed all parties can cooperate and work together to have a good outcome for all.