On the flip side of ammonia’s consideration, it tends to become corrosive to copper, brass and other non-ferrous materials when it combines with water. Copper is commonly used in refrigeration equipment for halocarbon systems. It’s not an option for systems using R-717. Another concern is its behavior with oil. As with almost any mechanical system, refrigeration systems require lubrication to reduce friction in moving parts extend their durability. Ammonia is non-miscible with oil, so systems in which it’s used must be designed to account for this characteristic and prevent oil from pooling in heat exchangers and thereby reducing efficiency.
But one characteristic that might be considered a drawback, and in fact has contributed to the lack of ammonia’s use in food retail, is in the applications where it is deployed; its odor. In concentrations above 50 ppm, ammonia is readily noticeable due to its pungent smell. It is in this sense self-alarming. In comparison to other refrigerants, consequently, this can actually be a benefit in that leak detection is made all the much easier. But too much of a good thing can be the opposite of a benefit.
On the basis of environmental and performance factors, ammonia would seem to be an excellent choice. But there are other considerations that come into play when assessing its practicality for various applications beyond industrial and distribution facilities’ use.
In a particularly a bad string of events in 2016 that included an ammonia leak at a Shamrock Farms facility in Phoenix which resulted that April in multiple people complaining of burning eyes. A month earlier, a Boston warehouse worker died from an ammonia leak. And a month before that, nine people were sickened from a leak at a Brazilian fertilizer plant. In December of 2015, two men working in a nitrogen plant in Canada were sent to the hospital after an ammonia leak. One succumbed to his injuries.
A meat processing plant in South Carolina experienced an ammonia leak in 2018 that fortunately did not result in any deaths or injuries. It did, however, cause an evacuation within a half-mile radius as a precaution at two in the morning.
More recently, in 2020, ammonia accidently released from a meatpacking plant in Texas killed more than 5,000 fish in a nearby creek. While ammonia systems are safe and efficient. provided the ammonia stays contained in the systems, as an article reporting the incident stated: “ammonia is highly corrosive and can injure or kill people who inhale it according to the U.S. Department of Health and Human Services.” It’s news like this that makes prospective users in consumer-facing business weary of its adoption.
Enough of practically any refrigerant by nature is more or less toxic in certain conditions. Most refrigerants however, besides being colorless are also odorless. R-717’s odor is distinctly noticeable even in very small concentrations. This means that since refrigeration systems are almost never entirely leak-proof, the prospect of a highly noticeable, highly toxic substance accidentally being released in a commercial public space has until recently been enough to almost completely forestall its use in food retail applications.
Ammonia’s Improving Prospects
More recently the business environment for commercial ammonia applications has been changing. With the adoption of new regulatory policies and technically innovative approaches, the food retail sector has begun to open up to the use of R-717. Under the EPA’s SNAP (Significant New Alternatives Policy) program the push for industry-wide adoption of natural refrigerants has gained significant momentum over the past several years that the program has been in place.
Starting in 2012, with one store in California, and more recently another two stores in California and Georgia, ammonia- based rack refrigeration systems have been installed. The three stores use low-charge NH3/CO2 cascade systems. Ammonia in a cascade system is used as a condenser, in the upper section of the cascade, for the CO2 in the lower section. Only the CO2 is sent out to the sales floor of the store while the limited amount of NH3 used in the system is kept entirely within the mechanical room (separate from the sales floor) and the piping to the outdoor condenser. Such a design entirely eliminates the risk of ammonia reaching public areas of the store.
The limited amount of ammonia employed in these systems, combined with improvements in lead-detection and monitoring allow stores like these to operate with virtually no risk to the public. It is consequently not difficult to see why ammonia may finally be starting to attract more consideration as a commercially useful refrigerant in the food retail sector.