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Case Study: Ammonia Release Incidents (2007 – 2017)

Refrigeration Basics

A refrigeration system is comprised of interconnected parts forming a system in which refrigerant is circulated for the purpose of cooling a designated space or surface. The refrigerant is circulated through a cycle of expansion and compression that allows for heat energy to be moved from one area to another via the refrigerant. Figure 1 and the accompanying cycle description illustrate this basic refrigeration cycle:

Basic Refrigeration Cycle
  1. The refrigerant enters the compressor as a low-pressure gas and is compressed into a high-pressure gas, heating the refrigerant.
  2. The heated high-pressure refrigerant gas enters the condenser, removing heat and condensing the refrigerant to a high-pressure liquid.
  3. Rapid expansion of the liquid refrigerant through the expansion valve rapidly cools the refrigerant resulting in a low-pressure liquid/gas mixture.
  4. Heat from the ambient air is absorbed by the cooled refrigerant, resulting in a low-pressure gas and cooling the refrigerated space. The cycle repeats.

Typical Refrigerants

System components and refrigerants are determined by the occupancy, system performance requirements and refrigerant classifications. There are several refrigerants that can be used in refrigeration systems: the refrigeration system designer would select the refrigerant based on compatibility (i.e., materials used in the construction and installation must be suitable for conveying the refrigerant), cost, efficiency and environmental effects. Table 1 identifies some typical refrigerants and their properties.

Beginning in the 1930s, chlorofluorocarbon (CFC)-based refrigerants were commonly used for their inert characteristics and low boiling points. The consumption and manufacture of CFCs has declined since the 1970s due to their environmental effects and has led to manufacturing and evaluating alternative refrigerants.

Ammonia (anhydrous ammonia or NH3) emerged as an alternative to CFC-based and hydrofluorocarbon-based (HFC) refrigerants. Ammonia occurs naturally in the environment in low concentrations as a by-product of microbial processes and from the decomposition of organic matter. It is also manufactured for a variety of uses in the agricultural, chemical, manufacturing and refrigeration industries. It is used in industrial heat extraction in sport and leisure facilities and in the food production industry for processing, preservation, cold storage and commercial retail systems.

Ammonia has a distinctive odour that is detectable at low concentrations. Even in low concentrations, ammonia can be irritating to the eyes, skin and breathing passages. Table 1 compares the properties and possible effects of ammonia and other refrigerants.


Refrigerant Hazards

While the refrigerant is contained in the system, it presents no hazard to people and the environment. A hazard may be presented when there is an uncontrolled, unexpected release of refrigerant from the system. These containment failures, or refrigerant leaks, are usually the result of one of two conditions:

  1. The refrigerant pressure has increased above the normal operating pressure of the container, component or system.
  2. A component, piping and/or system was compromised such that it will no longer hold the operating refrigerant pressure.

Potential health hazards to people exposed to refrigerant leaks and environmental hazards are identified in Table 1. Health hazards depend upon the type of exposure and can range from mild and temporary discomfort to irreversible serious damage to exposed tissues, or death. Injuries in BC have been reported as a result of ammonia releases and subsequent exposure to maintenance personnel or other people in the vicinity of the leak. As a result, this report primarily focuses on summarizing ammonia usage and incidents in BC within the context of other refrigerants and pressure vessels.

Table 1: Refrigerant Properties and Potential Effects

Refrigerant Anhydrous ammonia Halocarbon R22 R410A3 Halocarbon 134a 4
IUPAC Chemical name Ammonia Chlorodifluoromethane R-32/125 1,1,2,2-Tetrafloroethane
Chemical formula/composition NH3 CHF2Cl CH2F2(50%), C2HF(50%) C2H2F2
Refrigerant ASHRAE numb R-717 R-22 R-410A R-134a
Potential health effects - Acute toxicity

Corrosive to the eyes. May cause severe damage including blindness. Contact causes severe skin irritation and possible burns.

Ingestion causes burns of the upper digestive and respiratory tract.

Inhalation of corrosive fumes/gases may cause coughing, choking, headache, dizziness, weakness for several hours or death. 

Contact with liquid may cause frostbite.

High concentrations may cause asphyxia from lack of oxygen or act as a narcotic causing central nervous system (CNS) depression. 

Contact with liquid may cause frostbite.

High concentrations may cause asphyxia from lack of oxygen or act as a narcotic causing CNS depression. 

Intentional misuse and deliberate inhalation may cause death without warning. 

Higher exposures may cause temporary alteration of the heart's electrical activity or fatality from gross overexposure.

May cause slight irritation to eyes and skin. Contact with liquid may cause frostbite.

High concentrations may cause asphyxia from lack of oxygen or act as a narcotic causing CNS depression. 

Potential health effects - Chronic toxicity

Possible risks of irreversible effects.

Chronic exposure to corrosive fumes/gases may cause erosion of the teeth and jaw necrosis. 

Bronchial irritation, with chronic cough and attacks of pneumonia are common. Gastrointestinal disturbances may also be seen.  

Possible risks of irreversible effects. Possible risks of irreversible effects.

Possible risks of irreversible effects. 

Oxygen deficiency during pregnancy has produced developmental abnormalities in humans and experimental animals. 
Ecological effects

Harmful to aquatic organisms. Very toxic to aquatic organisms.

Ozone depletion potential.
Product is known to contribute to the destruction of the ozone layer. The environmental impact of this product has not been fully investigated.

Will not bioconcentrate. 

Ozone depletion potential.
Freezing point -77.7°C/ -107.9°F -160°C/ -245°F No information available -101°C/ -149.8°F
Boiling point / boiling range -77.7°C/ -107.9°F -40.8°C/ -41.4°F -51.6°C/ 60.8°F -26.5°C/ -15.7°F
Physical state Gas Compressed gas Compressed liquefied gas Compressed gas
Water solubility Completely soluble Slightly soluble No info available 67 mg/L at 25°C


1:      The Linde Group, “Ammonia Material Safety Data Sheet”, 2010
2:      The Linde Group, “Chlorodifluoromethane (Halocarbon R22) Material Safety Data Sheet”, 2010
3:      The Linde Group, “R410A Material Safety Data Sheet”, 2010 
4:      The Linde Group, “Tetrafloroethane (Halocarbon 134a) Material Safety Data Sheet“, 2010 
5:      Standard conditions: 25°C/77°F and 100 kPa/0.987 atm


Distribution of Refrigeration Systems in BC

The Boilers, Pressure Vessels and Refrigeration (BPVR) Safety Program at Technical Safety BC is responsible for overseeing the design, construction, installation and operation of refrigeration equipment and refrigeration systems, as well as boilers and boiler systems, pressure vessels, pressure piping and pressure systems throughout British Columbia. Technical Safety BC also certifies the operators of boiler, pressure and refrigeration systems.

BC Population Distribution –  Night View


Case Study - Ammonia - Figure 3


Case Study - Ammonia - Figure 4


Case Study - Ammonia - Figure 5

The highest population concentrations occur in BC’s Lower Mainland, Southern Interior’s Okanagan Valley and Vancouver Island’s East Coast. There are smaller concentrations in Central and Northern BC. The population density pattern is shown in Figure 2 and is mirrored not only in the distribution of the 80,000 operating BPVR units, but also in refrigeration units and ammonia refrigeration units as shown in Figures 3, 4, and 5.

Ammonia Release Incidents in British Columbia

Figure 6 compares the refrigeration units by refrigerants and shows that most refrigeration units utilize methane-or ethane-based refrigerants or methane-ethane-based blends.

Ammonia Case Study Final



Table 2: Refrigerant Listing

Refrigerant Number IUPAC Chemical Name


R-134a 1,1, 2, 2-Tetrafluoroethane
R-143a 1,1,1-Trifluoroethane (HFC-143a)
R-22 Chlorodifluoromethane
R-410 R-32/135 (50/50 blend of R-32 Difluromethane and R-125 Pentafluoroethane)


Carbon dioxide

Between 2007 and 2017, there were 74 incidents where it was reported that a refrigerant was discharged. Figure 7 compares refrigerant release incidents relative to boiler and pressure vessel incidents investigated by Technical Safety BC. Figure 8 shows refrigeration incidents and reveals that almost 80% of refrigerant release incidents reported to Technical Safety BC involved systems containing ammonia. A listing of the reported ammonia incidents is included at the end of this page.



Of the 57 incidents reported to Technical Safety BC between 2007 and 2017, 59 resulted in the release of ammonia from the refrigeration system. However, only 14 incidents included reports of injuries resulting from the incident. It is important to note that Technical Safety BC receives its injury reports from operators or first responders immediately following the incident. Ammonia exposure-related injuries may develop or the negative effects resulting of exposure may increase sometime after the initial reports to Technical Safety BC.

The following list summarizes the injury reports made to Technical Safety BC.

  • In 2008, an arena and the surrounding eight blocks were evacuated after an ammonia leak. It was reported that a first responder was exposed to ammonia.
  • In 2010, it was reported that a first responder was admitted to hospital after exposure to ammonia gas when responding to an ammonia leak at an arena.
  • In 2011, it was reported that three employees received injuries when ammonia refrigerant vapour was released at an arena. It was reported that two employees (operators) walked into ammonia vapour when they walked outside to investigate. The third employee (not an operator) reported exposure to ammonia. Approximately one year after the incident and investigation, Technical Safety BC learned indirectly that the third employee’s injuries were more serious than initially reported. This employee experienced chronic effects that impacted the employee’s respiratory systems.
  • In 2013, it was reported that 19 people were sent to hospital as a precaution after ammonia was released from a food processing facility. Of those, 18 people were from a separate facility nearby.
  • In August 2014, it was reported that an employee (operator) at an arena who was adding oil to the compressor and was sprayed with it, smelled ammonia . The operator used the face wash numerous times throughout the morning but did not seek first aid.
  • In October 2014, it was reported that three people were exposed to ammonia gas at an arena and were treated by emergency services and sent to hospital. They were released the same day.
  • In October 2014, an employee was sent to hospital for examination following an ammonia release at a food processing facility.
  • In April 2015, an operator attempted to purge ammonia from the arena’s system into water. The operator attempted to dispose the ammonia-water mixture via a hose. While initiating the siphon, the ammonia-water mixture entered the operator’s mouth.
  • In June 2015, three employees at a recreational facility were exposed to ammonia vapour when an operator in an adjacent building was purging an ammonia line.
  • In September 2015, an operator was attempting to add oil to the compressor when the operator was exposed to ammonia vapours. The operator was taken to hospital for treatment.
  • In December 2016, an operator sustained chemical burns to his hand when the operator attempted to replace an oil filter on the refrigeration compressor.
  • In December 2016, a worker (not an operator of the refrigeration system) experienced headache and burning/irritation in the nose after the worker was exposed to ammonia vapour.
  • In April 2017, a witness in the next building detected an ammonia odour after ammonia was released from the system’s safety relief valve.
  • In October 2017, three workers died after an ammonia release in an arena’s mechanical room.

Table 3 below summarizes the causes and failure descriptions identified by safety officers during their investigations of ammonia release incidents.

Table 3: Summary of Factors Contributing to Ammonia Release Incidents

Cause Category Qty Equipment or Operation Failure Description
  15 Component failure/wear out
  4 Control or monitoring system failure
  1 Failure of operator’s tool
  2 Component used incorrectly
   9    Inadequate or lack of preventative maintenance program and procedures  
  5    Procedure not carried out or inadequate
  4 Operating environment (e.g., higher than expected operating temperatures, higher humidity than expected, excessive vibration)
  2 Operator error/lack of training
  1 Access to area around maintenance work was not restricted
  3 System-component  compatibility
  1 Valve not secured when new component was installed
  1 Component missing
  1 Components (piping) misaligned
  1 Components not protected
  4 Not recorded

Ammonia Incident and Injury Summary

The number of BPVR incidents reported to Technical Safety BC is generally inconsistent between 2007 and 2010. Technical Safety BC has been actively working with these industry sectors to improve reporting and we believe this is the likely reason for the increase in reported incidents starting in 2010.

Between 2007 and 2017, there were 59 reported ammonia releases. Of these, 14 incidents resulted in 40 reports of ammonia exposure, including three fatal exposures. There are several contributing factors identified as being associated with the ammonia release as identified in Table 3. Most ammonia releases are associated with failures of control/monitoring systems or individual system components.

The reported ammonia releases occurred at recreational facilities (arenas) and food production/processing facilities.

Although there are exceptions, exposure and injuries are typically reported to be associated with the employees of facilities using ammonia or first responders attending to the incident.

Ammonia Release Incidents (2007 - 2017) are provided via a downloadable .CSV file.

Year              Incident Data
2007 - 2017 Data Set (.csv)

Table 4: Ammonia Release Incident Investigations

12-Jan-08 Accidental discharge of 200 kg ammonia. Not indicated. Arena 1 Ammonia exposure
27-Apr-08 After loud 'bang' was heard coming from the 'Ice house,' the fire department was called and responded to a report of an ammonia odour. A suction surge drum attached to the ice machine weld 'let go' and the tank seam opened. The weld on the 20" x 30" suction surge drum of the ice maker appeared of poor quality leading to a product failure. Food processing/ production 0 NA
5-Mar-10 Approximately 45 to 50 lbs ammonia was released. The facility "lost a condenser pump as it tripped out on high amps." A pressure relief valve opened and released the ammonia gas through the emergency discharge line. Not indicated. Arena 0 NA
11-Apr-10 Brine chiller tube leak which allowed high pressure ammonia to leak into the low pressure brine system. It was determined that the chiller had an internal fault. Arena 0 NA
17-Jul-10 Ammonia refrigerant entered a 'chill room' at an industrial facility. Corrosion to a 3/8-inch to a 1/4-inch forged steel bushing allowed it to split open and release ammonia. By design, the bushing had only a small amount of material available to resist pressure. 3/8- to 1/4-inch bushing has threads cut inside and outside to allow use as bushing and when external corrosion worked at the bottom of the outside threads to reduce the already small amount of material (less than 1/8 inch). The working pressure of the ammonia on the low side split open the strainer bushing with the strainer drain valve still attached. Avoiding use of forged steel bushings on the initial installation with thin side walls and also where exposure or corrosion is a possibility. Food processing/ production 0 NA
21-Oct-10 An ammonia leak occurred in the machinery room of a community ice arena. The plant operator and refrigeration contractor found the condenser motor did not start. With the failure of the condenser motor, the system temperature increased and the pressure rose to its limit (where the pressure relief valve opened). With the failure of this motor, an increase in system temperature and corresponding pressure resulted and rose to the point of causing the pressure relief valve to open. Each compressor is fitted with a high pressure limit that should have opened the circuit to the compressor, before getting to the point of relieving through the pressure relief valve. This did not occur as this safety device failed to operate. As recently as July/August of 2010, they were tested and all but two of the safety switches were replaced. This is one of the two that tested ok. Arena 1 Ammonia exposure
11-Nov-10 An ammonia leak occurred in the machinery room of an unoccupied arena. An employee was attempting to add oil to an ammonia compressor when he observed a leak (fill hose was not attached). Approximately 200 lbs ammonia was released. Qualified person was trained, but with minimal experience in this procedure. No written procedure was available, and an error Arena 0 NA
23-Nov-10 Ammonia was released at a recreational facility. A high pressure cut out switch failed to shut down a compressor when the compressor experienced a high pressure condition. Pressure continued to build until a safety relief device operated releasing ammonia gas to atmosphere via the relief stack, which triggered the ammonia alarm. The water supply line to the condenser had no protection and was subject to freezing during cold weather. The high limit switch was old (1986) and is mounted on the compressor base subjecting it to vibration. The safety relief operated as designed, venting gas to atmosphere, preventing a possible catastrophic failure. A high-pressure cut-out switch failed to shut down one of the compressors and as a result, a high pressure condition was created. One of four high limit switches failed to shut down its compressor. The high limit switch was old (1986) and is mounted on the compressor base subjecting it to vibration. Arena 0 NA
27-Oct-11 Employees at an industrial premise observed a leak from the freezer's evaporator coil. Corrosion to steel bushing allowed the ammonia to leak in the mechanical room housing the evaporator coils. Food processing/ production 0 NA
12-Nov-11 An ammonia leak occurred at a commercial-industrial facility. Approximately 10 lbs ammonia entrained in approximately 200 litres of compressor oil was released when a suction side 3/8-inch pressure sensing line failed. The suction side The 3/8-inch stainless steel tubing within the compression fitting failed when a circumferential crack completely fractured. The crack within the 3/8-inch stainless steel compression fitting did not show up on external inspection. Metal fatigue appeared to be a factor, along with unit vibration and initial metal stress within this type of compression joint. The refrigeration contractor identified the main cause and factors leading to the failure as a severe vibration condition of the compressor. This severe vibration condition only occurs when only happens when the control slide valve is at, or at near its minimum position. The vibration was so intense that the contractor immediately shut the compressor down. Also, the contractor's investigation discovered the 'PHD' vibration monitoring system was inactive. When the monitoring system was activated, the compressor in fact shut down on 'high vibration.' Food processing/ production 0 NA
28-Nov-11 Approximately 400lbs ammonia refrigerant was released to atmosphere from a safety valve on the outdoor refrigerant condenser. At shift change, an uncertified operator was made aware that two ammonia refrigeration compressors had been short-cycling from 0400 Hrs (low suction pressure). The operator then opened the suction by-pass valve to a second chiller. Both ammonia compressors started then quickly tripped. The operator reset both high pressure limits. This process was repeated. The ammonia condenser safety valve lifted, and when the operators walked outside to investigate they both walked into ammonia vapor. A third compressor continued to cycle and lift the safety valve for one hour (400 lbs ofÊ ammonia released). Condenser pump controller (Johnson Controls/Penn P70AA-119, J0019, range 50/300 psig, opens low) fails after 6 months Arena 3 Ammonia exposure
30-Nov-11 Approximately 300 lbs ammonia was released when two maintenance contractors attempted to transfer ammonia from aÊ liquid receiver to a storage bottle. While attempting to purge the transfer hose, the ratchet wrench on the isolation valve failed to operate in the reverse direction. The maintenance contractor inadvertently opened the valve wider, allowing the release The primary cause of the release was due to a ratchet wrench which failed to operate correctly (i.e., in the opposite direction). Arena 0 NA
28-Feb-12 Approximately 75 lbs liquid ammonia was released into the machinery room at an industrial facility when a gasket failed on the cap of a liquid level controller for a refrigeration vessel. Examination of the cap on the liquid level control revealed impact damage. This damage is the result of the occasional physical removal of ice. Over time the cap loosened causing liquid ammonia to leak by the cap gasket. The initial attempt to tighten the cap resulted in fracturing the fibre gasket. Incorrect procedures, inadequate staff training and poor quality control also ontributed. Some written procedures and emergency instructions were in place but not entirely followed. Food processing/ production 0 NA
20-Jul-12 An ammonia leak occurred at a commercial facility. The leak occurred at the compressor and was isolated by the shut-off valves. Normal wear and usage on the compressor was observed where the mechanical seal failed. Food processing/ production 0 NA
12-Sep-12 At a recreational facility, the ammonia LED sensor display indicated 7ppm. An ammonia leak was detected and isolated to the compressor #2 suction valve. It was reported to the safety officer that the contractor installed the suction valve without securing (tightening) the valve bonnet. In addition, the bolts may not be to specification and may not have been threaded to depth properly at the flange connections to the associated valve piping. Arena 0 NA
4-Nov-12 Approximately 100 lbs ammonia was released into an unoccupied processing room of an industrial facility when a pressure gauge failed on the liquid line to an ammonia evaporator. Inspection revealed that a second pressure gauge (on the hot gas line for the same installation) was pinned at maximum pressure. Both pressure gauges had a range of 0 to 150psi and were installed in a system with an operating pressure of Food processing/ production 0 NA
18-Jan-13 The recreational facility's ammonia alarm sounded when the ammonia concentration was detected at 25 ppm. The fill line was already open when an operator attempted to connect the portable tank's flexible hose. Because the line was open, when the operator was threading the flexible hose onto the charge line, the port valve discharged ammonia and blew the flexible hose away. Arena 0 NA
6-Mar-13 The shift engineer observed that the ammonia leak monitor was in alarm (>35 ppm). When the shift engineer activated the control system reset, the system failed. With no condenser fans or pumps in service, the high pressure discharge quickly exceeded the relief valve settings and two relief valves were activated, resulting in approximately 500lbs ammonia released to atmosphere. "High Liquid Level" in the Low Temp Suction Accumulator (for Frick #1) shuts down all plant equipment (in the main compressor room) via the "control system" (this also shuts down the evaporative condenser fans and water pumps). Frick #2 (in auto control) starts up on local controller call (during the plant "trip"). With no condenser fans or pumps in-service, the high pressure discharge quickly exceeds relief valve settings (250 psi) and two relief valves are activated (one does not reseat).This 1970 vintage plant has had at least two Food processing/ production 0 NA
15-May-13 Approximately 200 lbs ammonia was released to atmosphere from a refrigeration system at an industrial facility when a compressor controller and control system failed. Two of the eight condenser relief valves were activated. High Liquid Level (in the Low Temp Suction Accumulator) initiated a shutdown of all plant equipment via the plant control system. However, during the investigation it was discovered that the plant control system does not shut down the Frick #2 compressor, and the NH3 liquid pumps, which are associated with the remote "High Temp Air Chill System". Frick #2 compressor continued to Food processing/ production 19 Ammonia exposure
17-Jan-14 A retaining bolt disengaged from the manway door yoke on the oil separator of an ammonia screw compressor. A second retaining bolt remained loosely in place. Pressure cycles and transmitted compressor vibration resulted in gradual loss of bolt torque and then movement of the bolt in the slotted yoke, until the bolt slipped out of the yoke. An inadequate routine maintenance procedure and lack of knowledge contributed. Arena 0 NA
8-Jul-14 The fire department responded to the plant's fire/ammonia alarm. The defrost line to the ice cream room cooler isolation valve failed and the relief valve in the same line also lifted. There was poor documentation to prove adherence to risk-assessed plant requirements. Food processing/ production 0 NA
30-Jul-14 An ammonia leak occurred at an industrial facility. An approximately six-inch crack at the fillet weld along the edge The leak occurred on one of the plate elements on plate freezer #3. The plate freezers have horizontal plate elements which can be manually raised or lowered using hydraulic controls. Food product is frozen using the refrigerant filled plate elements. The plate freezer elements were moved using hydraulics with no product to freeze between the plates. Excessive forces on the plate elements caused an approximately six-inch crack at the fillet weld along the plate edge. As a result ammonia refrigerant was released into the atmosphere. The hydraulics are operated manually and have no limit switches. Personnel operating the equipment were given instructions that were not clear enough or misunderstood. The plate freezers are designed to have fish in between them when being operated into the freezing position. Food processing/ production 0 NA
22-Aug-14 Approximately 200 lbs ammonia was released to atmosphere. The condenser safety valve activated due to 'no cooling' in the condenser while the ammonia compressor was operating. While restarting the plant after a power failure, the operator forgot to start the condenser circulating pump (which should be started before starting the compressor). The compressor was started without condenser cooling, and as a result, ammonia gas temperature began to rise, thus raising the gas pressure in the system. Eventually the gas pressure rose more than the safety valve setting, activating the safety valve which released the ammonia to atmosphere.The compressor's high pressure safety cut off did not activate. The high pressure cut off is supposed to activate and shut off the compressor unit when the system senses a high pressure condition. Food processing/ production 0 NA
22-Aug-14 While in the process of adding oil to a compressor, an employee was sprayed in the abdomen with some oil from the compressor. Upon smelling ammonia, he immediately left the area and activated the ventilation system on the way out. He left the valve to the compressor open and it continued to spray out the remaining oil. The compressor was off but some ammonia escaped into the room. The operator thought he had turned the valve off before he proceeded to remove the connecting oil hose; he had not. In fact, he indicated that the direction he turned the valve caused it to become more open. Arena 1 Ammonia exposure
30-Aug-14 An ammonia leak occurred at a fish production facility. During normal operation at the production facility, a 1/4-inch pipe fitting broke off a liquid ammonia pipe line in the glaze freezer. The glaze freezer is a large room (approximately 60 feet x 60 feet x 18 feet high). The overhead liquid ammonia line is located approximately four feet below the ceiling of the glaze freezer. The forklift operator raised a basket too high and broke a 1/4-inch fitting off the ammonia pipe line. Food processing/ production 0 NA
6-Oct-14 Ammonia was released from Compressor Nylon #4 mechanical seal. The shaft seal ring let go from deterioration, allowing oil and ammonia to leak. The deterioration over time in normal operating conditions. Food processing/ production 0 NA
6-Oct-14 Approximately 300 lbs ammonia was released to atmosphere at a recreational premise (arena). The plant was allowed to run to cool the ice surface down prior to commencing with the installation of pipe fittings on the glycol line for the compressors. Two high pressure excursions were created when the faulty high side float was put in auto mode. The high side float was manually operated in the open position prior to the release because it was prone to getting stuck in the closed position. Evidence suggests that the second high pressure excursion never reached the 250 psig set pressure of the condenser pressure relief valve and that the valve lifted early. The two compressors had to be manually shutdown upon discovery A faulty high side float caused the two high pressure excursions. An overdue pressure relief valve replacement interval and an installation in the wrong orientation may have contributed to the early release. The lower discharge point and the northerly wind could have resulted in more of the ammonia being concentrated on the north end Arena 3 Ammonia exposure
30-Oct-14 A release of approximately 25 lbs ammonia vapours occurred at a poultry processing plant. The ammonia vapour was released when hot gas ammonia piping in the packaging room ruptured. The hot gas ammonia piping that failed was constructed of NPS 3/4 schedule 80 carbon steel material. This piping was supported by a pipe hanger constructed of stainless steel material. The piping was uninsulated and was in direct contact with the hanger. Food processing/ production 1 Ammonia exposure
5-Nov-14 A chemical analysis report indicated ammonia was present in the system's brine solution. Not indicated Arena 0 NA
10-Nov-14 Approximately 75 lbs ammonia was released to atmosphere. An operator turned on the Mycom 200 compressor and a smell of ammonia was detected on the outside of the building soon after. No significant ammonia smell was detected inside the mechanical room by the operator. The compressor was immediately shutdown to stop additional ammonia from escaping. The release was blamed on the pressure relief valve on the Mycom 200 compressor economizer lifting and releasing ammonia out the pressure relief discharge stack on the roof. The pressures noted on the compressor during the incident were within normal operating ranges (131 psig). The compressor operating limit, high pressure limit switch (190 psig) and the common high pressure limit switch (200 psig) were never activated during the incident. The pressure relief valve was tested. The valve leaked heavily during the pre-test but still popped at its set pressure of 250psig. The valve was within the required 5yr replacement interval. Since the pressure relief valve lifted as designed it can be concluded that the pressure exceeded the set pressure of the operating limit and the two high pressure limits. None of the devices caused a shutdown of the compressor. No records of annual testing and calibration of these devices could be provided as required by Food processing/ production 0 NA
28-Nov-14 Between Nov 28, 2014 and Dec 1, 2014, approximately 2,000 lbs ammonia was released to atmosphere due to a leaking pressure relief valve at a food production facility. There were no visible signs of ammonia leakage although there was a strong odour of ammonia reported. An employee noticed that the motor overload alarm on #3 compressor was triggered and the control panel indicated that the spray pump was in the OFF position. The refrigeration plant consists of four Vilter refrigeration compressors. Two compressors are operated and the third compressor remains on standby. The #4 compressor is rarely operated, but the discharge valve is left open as there is a check valve in the system. On Friday, November 28th, 2014 #2 & #3 compressors were operating and #1 compressor was on standby. Food processing/ production 0 NA
17-Feb-15 Ammonia leaked from the blast freezer refrigeration system at a poultry processing plant. The blast freezer is located in the main freezer and has restricted access. Personnel enter the freezer once a day to load and unload the poultry. This blast freezer is operated off the low-temperature liquid receiver (the system normally operates under negative pressure) located in the machinery room. During planned servicing of the low-side compressor, the three-hour downtime resulted in system Food processing/ production 0 NA
21-Apr-15 "A leak on the south coil of the ammonia plan evaporative condenser was discovered. The operators isolated the coil and proceeded to bleed the remaining ammonia from it. Several attempts were made to bleed to atmosphere at the coil outlet. The first attempt was conducted for approximately 30 minutes. As a result of this controlled release, ammonia was drawn into the fresh air intake of the arena change room air-handling system approximately 27 feet away. A second attempt to bleed the coil was made, this time to water, for about 15 minutes. This attempt was stopped due to the strong ammonia odour. Not indicated Arena 1 Burns in the mouth from ammonia-water mixture
7-May-15 Less than one pound of ammonia was released from a leak on the low-pressure control on Compressor #2. Low-pressure pressure switch diaphragm failure on the compressor. Arena 0 NA
11-Jun-15 A technician was bleeding (purging) an ammonia line outside of the arena building adjacent to the condenser. Ammonia vapours entered the building, exposing three people to ammonia vapours. An ammonia-rated half-inch diameter hose was attached to the piping connection and ammonia vapours were allowed to escape through the hose into two 45-gallon drums filled with cold water. The containers were not covered when the refrigeration line was purged. Arena 3 Exposure to ammonia vapour
28-Jul-15 Approximately half a kilogram of ammonia was released to atmosphere due to a leak in the hot gas strainer gasket. The cold room was operating in warmer temperatures than normal and an employee found the hot gas timer stuck in the 'ON' position, leaving the hot gas line charged with 140-150 psi ammonia gas for an unknown period of time. This condition caused the deteriorated gasket in the strainer on the hot gas defrost line to fail and start leaking liquid ammonia. Food processing/ production 0 NA
10-Sep-15 The threaded fitting connecting the tubing line to a pressure switch became loose, which allowed ammonia gas to enter the machine room, triggering the leak detection system. Not indicated Arena 0 NA
20-Sep-15 Approximately 140 pounds of ammonia was released to atmosphere. The fill valve was not closed completely after adding oil to the compressor. The pressure inside the compressor pushed out oil and ammonia refrigerant. An operator was taken to hospital for exposure to ammonia vapours. The facility did not have a procedure in place for adding oil to the compressors. As a result, isolation of the line was not confirmed prior to disconnecting the hose fittings. Arena 1 Exposure to ammonia vapour
24-Sep-15 Approximately 200 pounds of ammonia was released into a cold storage area at a food and beverage producing facility.Ê An operator dropped a heavy line onto the valve (fitting) of an ammonia oil drain, causing it to crack and release ammonia. The fitting was an ammonia oil drain line on an evaporator surge drum. The oil drain piping and valve were exposed and susceptible to damage. Food processing/ production 0 NA
4-Nov-15 Approximately half a pound of ammonia was released outdoors at a food processing facility. During a routine maintenance procedure, an unplanned high pressure condition resulted in the activation of the relief valve on a pressure vessel (oil pot). The employee was draining the oil, which is a routine maintenance procedure. As the isolated oil pot (pressure vessel) warmed up the liquid ammonia, it vapourized, causing the pressure to rise until the relief valve lifted. The employee was not following the current procedure, and the procedure used had inaccuracies. Food processing/ production 0 NA
26-May-16 A small quantity of ammonia was released from a refrigeration system at a commercial dairy plant. The plant was evacuated when the ammonia low level alarm detector activated on the production floor. The maintenance employee verified ammonia level on alarm panel at 110 parts per million and upon investigation a leaking solenoid valve was isolated from the refrigeration system. Based on the timing of the failed solenoid coil and the evidence of overheating on the plunger and deteriorated coil housing, it is highly probable the heat transferred to the bonnet gasket caused a premature failure resulting in the ammonia leak. Additional contributing factors are the age of the gasket and the continued replacement of fuses without determining the cause of the electrical short. Food processing/ production 0 NA
28-Jul-16 The operator at a recreation centre reported an ammonia release. Ammonia vapour leaked into the brine circulation loop from a damaged chiller, saturating the liquid with ammonia and causing ammonia alarm to go off in the machinery room. It is probable that the cause of this incident was insufficient preventative maintenance coupled with equipment approaching the end of its lifespan. A likely contributing factor was the increased pressure in the chiller due to seasonal operating conditions. Arena 0 NA
5-Dec-16 Approximately 15 kg ammonia was released when an operator atttempted to change out an oil filter. Instead of opening the valve that would allow oil to drain, the operator opened the ammonia line. The operator sustained an chemical burn. There are several factors that contributed to this incident: Food processing/ production 1 Chemical burn on hand
30-Dec-16 Maintenance workers were performing maintenance on the refrigeration system. Ammonia was purged by air to allow maintenance workers to work on the system. Ammonia was purged through a hose to a water-filled tote (repository); the hose end was submerged in water to absorb the purged ammonia vapour. An employee (not a maintenance operators) was working in open area near the location of the maintenance work was occurring. The maintenance workers told the employee that ammonia was being released and to stay away from the tote. Later, employee removed the tote's lid and hose from the water and was exposed to ammonia vapour. The area around the ammonia hazards was accessible to other employees who may not understand hazards associated with ammonia exposure. Food processing/ production 1 Headache, burning sensation in the nose from exposure to ammonia vapour
2-April-2017Ê Approximately 125 lbs of ammonia was released through the safety relief valve while in operation. A witness reported the ammonia odour. The plant and arena were vacant at the time of the incident. The pressure relief valve may have lifted prematurely. The pressure relief valve bench test demonstrated it lifted prior to the 250 psig set pressure. Arena 1 One person detected the ammonia odour
20-Apr-17 A crack developed in an internal tube within the condenser. This allowed ammonia to leak, causing a low level alarm to activate. The age of the equipment may have been the cause and contributing factor Arena 0 N/A
24-May-17 The manhole gasket seal on an oil separator failed to hold ammonia in the vessel, which resulted in the exhaust ventilation system to be activated. The gasket failed before recommended service life and replacement. Its likely that over-torquing on the manhole cover against the flanged connection damaged the gasket Food processing/production 0 N/A
2-Jun-17 Ice that fell from exposed ceiling rafters in a commercial freezer broke a threaded connection of a pressure gauge mounted to a pressurized vessel on the refrigeration system, causing a leak of pressurized ammonia. Ice formed and accumulated on the exposed rafters directly above the pressure gauge. Food processing/production 0 N/A
5-Jul-17 Ammonia was released from the pinhole in the piping to the hydro cooler surge drum. The ammonia vapour was pulled in by the inlet air louvers by the continuous vent fan. The cold temperatures of the insulated ammonia liquid supply line created condensation between the piping and insulation. The insulation becameÊsoaked with moisture, and was not able to drain nor dry. Food processing/production 0 N/A
14-Aug-17 Oil and ammonia leaked from the compressor and into the machinery room. It is probable that the broken threads of the half-inch service valve on the compressor caused the leakage. Food processing/production 0 N/A
4-Sep-17 Nipple (fitting) between oil separator and its relief valve cracked and failed to hold ammonia in the piping which resulted in the exhaust ventilation system to be activated. It is likely that a combination of vibration-induced cracking and incompatible fitting material caused it to crack open.Ê During the refrigeration cycle, the compressor starts automatically and stops when enough compression is accomplished. This continuous cycle generates vibration, which is transferred to the piping system and vittings. Fittings and components made of certain materials are incompatible with ammonia and degrade quickly in its absense (e.g., copper and copper alloys) Arena 0 N/A
26-Sep The liquid ammonia transfer pump gear shaft O-ring failed thus allowing the liquid ammonia to leak into the ammonia compressor room. The compressor room ammonia refrigerant leak detection system activated. The O-rings were approximately 17 years old and had become less pliable and lost their sealing capability. The O-ring showed signs of fretting when it was removed from the pump. Parts for the pumpÊare difficult to find so there was a reluctance to service it. Food processing/production 0 N/A
17-Oct- Incident currently under investigation. Incident currently under investigation Arena 3 Fatal
24-Oct-17 The suction regulator O-ring on an ammonia refrigerant system failed and allowed ammonia gas to leak into a room where production workers were present.ÊAn employee noticed a faint smell of ammonia and evacuated the workers as a precaution. The suction regulator bottom O-ring was found to be "blown out" and this allowed the ammonia gas to leak into the room. It is likely the O-ring was subject to varying temperatures and pressures throughout the day and over time the mechanical properties of the material declined. Food processing/production 0 N/A
27-Dec-17 The bonnet gasket on the isolation valve between the brine chiller and the oil pot leaked approximately 10 lbs ammonia into the mechanical room. Two refrigeration technicians drained oil from the oil pot and when the isolation valve was closed, the bonnet gasket leaked ammonia into the brine chiller insulation. It is probable that the contributing factors of the gasket leaking was the continuous use of additional force in opening the valve when ice had built up on the valve. Arena 0 N/A