One thing you can usually count on when you see a news article about an ammonia release is that the reporter is unfamiliar with ammonia refrigeration. That’s not surprising – they can’t be expected to know everything! This article is an attempt to provide some basic information to reporters so they can write a more cogent article. I’ll update this as I find some more common misconceptions.
What is it?
Ammonia is naturally produced by the anaerobic decay of organic material. First isolated by Joseph Priestley in 1774, it is the combination of one Nitrogen atom and three Hydrogen atoms. It is a colorless gas that is about half the weight of air. It has a boiling point of -28f and about 150 million tons a year are produced commercially from natural gas.
Most people are familiar with the smell of ammonia from its use as a household cleaner which contains 5% ammonia and 95% water.
Why is it used?
About 85% of the ammonia produced in the world is used as a fertilizer. Most commercial dairies, meat packing plants and distribution centers however use it as a refrigerant. Ammonia is an extremely efficient refrigerant that is relatively inexpensive. It is the most environmentally friendly refrigerant in widespread use because it has zero global-warming potential and no effect on the ozone layer.
Where is it located in a facility?
The bulk of the ammonia in a refrigerated facility is usually in the Compressor Room. Ammonia liquid is piped to various heat exchangers throughout a facility to provide cooling in those areas. Some facilities use a secondary loop of glycol or another refrigerant. In those facilities the glycol or other refrigerant is piped to the heat exchangers and the ammonia stays in the Compressor Room and on the roof near the compressor room in the Condensers.
What can happen if I am exposed to it?
Ammonia has a strong irritating pungent odor that most people can detect at 5ppm (parts per million of air). The Occupational Safety and Health Administration (OSHA) has set an acceptable eight-hour exposure limit at 25ppm and the IDLH (Immediately Dangerous to Life and Health – the level to which a healthy worker can be exposed for 30 minutes without suffering irreversible health effects) for ammonia at 300ppm. In my experience, people will voluntarily leave the area at concentrations well below 50ppm. Most facilities have ammonia detectors that detect leaks and notify the system operators that there is a problem. Ammonia is not a carcinogen. Prolonged exposure to minor amounts does not result in bioaccumulation in people and can not cause any known adverse health effects.
High concentrations of Ammonia Gas or Ammonia Liquid are extremely dangerous. Ammonia is highly corrosive to skin and can cause irreversible damage to eyes. It is Anhydrous, meaning “without water” and will merge with moisture to form ammonium hydroxide, a caustic. This caustic will form on moist areas of the body causing chemical burns. Liquid ammonia at ambient air pressure will be 28 degrees below zero and can freeze exposed flesh on contact.
If exposed to liquid or high concentrations of vaporous ammonia, flush the area with copious amounts of water for at least 15 minutes and seek medical attention.
What are the environmental effects of a release?
Ammonia is extremely toxic to fish and amphibians since they cannot metabolize ammonia – this is one of the reasons aquariums have charcoal filters, to remove the ammonia that normally occurs from decay of organic material. Water with extreme amounts of ammonia in it can also harm the bacteria in sewage plants, although this is fairly uncommon. Vapor clouds of ammonia will harm vegetation from caustic burns. This is the same thing that can happen if you put fertilizer full strength on your garden.
Ammonia is not very stable when released in the environment and will usually decay into atmospheric nitrogen and water within a few days. Usually it will not last those few days as it is rapidly taken up by plants and bacteria. Ammonia does not build up in the food chain because it serves as a nutrient for plants and bacteria.
What are all these “valve failures” about?
If a news article mentions a reason for a release, it’s almost always called a “valve failure” or “valve malfunction”. Ammonia systems are equipped with pressure relief valves that operate if the pressure of the system exceeds the rated pressure of the equipment. This is required by law and the reason is fairly obvious: if you must release dangerous pressure in the system you would rather do it in a controlled manner rather than in some big explosion as a vessel catastrophically fails! Once this pressure is released the pressure relief valve should re-seat. Occasionally these relief valves can stick in the open position and dump the entire system charge. In a properly running ammonia refrigeration system these valves should NOT operate – sadly, many times incorrect system operation causes these valves to open and the operator reports it as a “valve malfunction” when the system was running outside of its design and the valve was actually operating correctly.
Actual “valve failures” are rare although they do occur – it’s an imperfect world.
Isn’t ammonia explosive!?
Ammonia can indeed burn in the range of 15-28% (150,000-280,000PPM) concentration in air. This is a VERY rare occurrence and would usually only happen when something has gone terribly wrong in the Compressor Room. The temperature of an ammonia flame is very close to the temperature required to ignite the mixture so there has to be a catalyst of some sort. In a Compressor Room this would usually be the compressor oil separator catastrophically failing and releasing a fine mist of oil into the air. For comparison, Gasoline can burn in much lower concentrations: 1.4-7.6% (14,000-76,000PPM)