Asphyxiation Accidents in Refrigeration
In this article, we explore Asphyxiation as a personal safety hazard associated with Refrigeration. In the last article by the author, published in December 2017, we discussed about Legionnaires Disease…
- C Maheshwar
Asphyxiation is defined as deprivation of oxygen leading to unconsciousness or death. Atmosphere contains 21% of oxygen. Human body needs a certain amount of oxygen in the atmosphere. Lesser amount of oxygen content in the atmosphere below a threshold of 12%, stimulates some self-protective and self-regulatory mechanisms which sustains for a little while, beyond a certain time period, exposure to Oxygen deficient atmosphere causes severe disturbance to the bodily functions and in extreme cases can lead to death. Approximately, 5% of volume of air is consumed in each breath (about 21% O2 in and about 16% O2 out).
Figure 1: Safety Sign of Asphyxiation hazard
How much Oxygen is there for a person to survive in an air-tight enclosure?
0.617 kg of Oxygen per day for an average person at rest;
0.84 kg for an average person going about his regular duties, including sleeping and
7.2 kg for an average person that does continuous heavy exercise day and night
How long would it take to use up all the O2 in 1 cubic metre (1 m3 of space at sea level)?
0.48 days; 0.36 days; and 0.042 days respectively.
How long would it take to use up all the O2 in 1 cubic metre (1 m3 of space at sea level)
0.48 days; 0.36 days; and 0.042 days respectively.
According to psu.edu the lowest % Volume of O2 a person can survive at standard pressure is about 17.5%. How long would it take to use up just the O2 in 1 m3 for life?
2 hrs; 1.5 hrs and 10 minutes respectively.
What about other spaces such as rooms, houses, etc.? How long would one person last?
Room: 12 ft wide x 12 ft long x 8 ft ceiling or 3.6 m x 3.6 m x 2.4 m of volume:31.1m3 2.6 days; 1.9 days; and 5.3 hrs respectively
Figure 2: Amount of Air Breathed by Children
Figure 3: Amount of Air Breathed by Adult Females
Figure 4: Amount of Air Breathed by Adult Males
Oxygen Deficient Atmosphere
Effects of Exposure to Oxygen Deficient Atmosphere
• 15 – 19% O2- Co-ordination impaired
• 12 – 14% O2- Perception and judgment impaired
• 10 – 12% O2- Performance failure, poor judgment
Onset of Cyanosis
• 8 – 10% O2- Mental failure, unconsciousness
• 6 - 8% O2- 100% fatal after 8 minutes exposure
• 4% O2- Coma in 40secs, convulsions, death
Types of Asphyxiation Accidents
Asphyxiation Accidents could be of two types:
a) Due to leaking refrigerants
b) Due to release of gases from refrigerated products
Aphyxiation due to leaking refrigerants
Incident 1: Asphyxiation of a 24-year-old male assistant manager of a shopping mall ice skating rink inside a compressor room while attempting to shut off a refrigerant gas (R-22) leak
On May 20, 1991, a 24-year-old male assistant manager for a shopping mall ice skating rink was asphyxiated inside a compressor room while attempting to shut off a refrigerant gas (R-22) leak. The incident site was a refrigeration system compressor room that served an ice skating rink located within an indoor shopping mall complex. The compressor room measured approximately 25 feet long by 20 feet wide by 10 feet high; it was accessible through two self-closing steel doors (one double door, and one single door) located at opposite ends of the room. The compressor room was 4 feet below the ground-level floor of the shopping mall. The refrigeration system installed there had a maximum capacity of 4,000 pounds of R-22 refrigerant. It is about three times denser than air, with a relatively high vapor pressure at room temperature.
Two months before the incident, several slow leaks of R-22 during routine equipment checks had been reported. Nine days before the incident, R-22 leaks at the filter flange pipe were noticed. Two days before the incident, someone had attempted to stop a pinhole-sized leak in the filter flange pipe by tightening the pipe with a wrench, causing a section of pipe to break off, and produced a much larger leak. Someone then plugged this leak by driving a makeshift plastic plug into the flange hole and sealing it with a putty-like material.
About 8:00 am on the day of the incident, a shopping mall maintenance worker performing routine maintenance checks, observed refrigerant oil “oozing” from under the doors to the compressor room. He could not open the locked doors, but he heard a “hissing sound.” Looking through a crack between the doors, he saw the lower part of the compressor room engulfed in a “Freon mist,” 4 feet deep. He left the area and reported the problem to the maintenance supervisor.
About 8:30 am, the maintenance supervisor entered the compressor room wearing an organic vapor cartridge gas mask. He attempted to isolate the leak but became disoriented. He de-energized the refrigeration system at the circuit panel and exited the compressor room. However, since the refrigerant was still under pressure, it continued filling the room. He complained that his chest hurt, and that his heart was racing. He reported the leak to the maintenance manager. By this time, about 685 pounds of R-22 refrigerant had leaked out of the refrigeration system.
The victim (assistant ice rink manager) arrived at the ice rink at about 8:40 a.m., and entered the compressor room along with maintenance supervisor, and maintenance worker, carrying tools and wearing a cartridge-type respirator. This type or respirator provides inadequate protection in an oxygen-deficient atmosphere. The self-closing doors to the compressor room closed and automatically locked behind them to bar entry to, but allow exit from, the room.
By about 8:50 am, some of the leaking CFC-22 had flowed from the compressor room into an adjoining health club pool area where two male patrons were swimming. Both patrons found it difficult to breathe, and had to be rescued from the pool and they subsequently recovered.
About 8:56 am, after hearing a noise “like a bang or a pop,” the ice skating director unlocked and opened the compressor room door. She saw the maintenance supervisor and maintenance worker #2 lying on the floor at the foot of the stairs, but did not see the victim, whom she knew was present. The victim was hidden to her view on the floor behind some refrigeration piping.
The firefighters and EMS team arrived at the scene at about 9:00 am. The slipperiness of the refrigerant oil which covered the compressor room floor and the clothing of the two injured workers made the rescue effort extremely difficult. Firefighters in full turnout gear and self-contained breathing apparatus (SCBA) entered the compressor room, located maintenance worker #2 and maintenance supervisor and removed them from the room.
By about 9:20 am, a total of 3,200 pounds of refrigerant had leaked out of the refrigeration system. The victim was not in plain sight, having fallen behind some refrigerant equipment and piping, and being covered with the mist. He was finally located at about 9:22 am. and was removed to the open air immediately outside the building. The victim received both CPR at the scene, and on the way to a local hospital, where he was pronounced dead by the attending physician. The maintenance supervisor and maintenance worker were transported to a local hospital where they subsequently recovered. The medical examiner listed the cause of death as asphyxiation by oxygen displacement with refrigerant (R-22).
Incident 2: Junior officer in a ship became unconscious while asleep because of leaking refrigerant vapor from the AC Blower Room Source: DOLTHOYS September 2006
A cadet in a ship became unconscious while asleep because of leaking refrigerant vapor from the AC Blower Room which got drawn into the Evaporator Blower and was carried along with the cold air into the accommodation spaces. His cabin was the closest to the AC Blower Room.
Accommodation air conditioning starboard side fan unit bearing broke down while running. The shaft along with the fan fell on the evaporator unit and damaged it. Four tubes of the evaporator got punctured and there was a heavy leakage of Freon refrigerant inside the AHU room. The extent of damage to the bearing, the shaft and the evaporator coil can be seen from the photographs. Through the air conditioning ducts, the leaking Freon got carried away into the accommodation. The air conditioning plant was stopped immediately. All crew were informed and accommodation was ventilated. One deck cadet was found unconscious in his cabin. He was taken outside into the fresh air and was revived. Rest of the crew was found safe.
Figure 5: Damaged AC Blower
Figure 6: Damaged Evaporator tubes
Accommodation air conditioning blowers are generally situated outside the engine room in air handling rooms which form part of the accommodation / superstructure.
1. Because of their location, they tend to get neglected, often waterlogged because of condensation, dirt from insulation which gets dislodged and peeled off due to vibration.
2. No machinery will breakdown suddenly. There will be signs of degeneration which should be noticed by diligent watch keepers. If noticed sufficiently in advance, corrective action can be taken and major damage and disaster can be avoided.
3. The Planned Maintenance System is designed to prevent breakdowns of such nature. It is important that shipboard personnel give due importance to preventive maintenance of machinery by following PMS in totality. Otherwise, PMS simply becomes a futile exercise.
4. The above incident could have been fatal.
Figure 7: Process of Respiration
Figure 8: Respiration Rate vs Oxygen content
Bottom Line: Out Of Sight Does Not Mean Out Of Mind!
Incident 3: A reefer mechanic became unconscious immediately after entering AC Blower Room
A reefer mechanic became unconscious immediately after entering AC Blower Room as the room was having dangerously low oxygen content due to leaking refrigerant vapor from the reefer machinery.
Incident 4: Release of Ammonia from a packing plant slaughterhouse
In a 1986 incident in a packing plant slaughterhouse, a refrigeration line ruptured, releasing ammonia. Eight workers were critically injured, suffering respiratory burns from ammonia inhalation, and 17 others were less severely hurt.
Incident 5: Release of about 45,000 pounds of Ammonia in a frozen pizza plant
A 1989 ammonia release in a frozen pizza plant led to the evacuation of nearly all of the 6,500 residents of the town where the plant was located. The release started when an end cap of a 16-inch suction line of the ammonia refrigeration system was knocked off. Up to 45,000 pounds of ammonia was released, forming a cloud 24 city blocks long. About 50 area residents were taken to hospitals, where they were treated with oxygen and released, while dozens of others were treated with oxygen at evacuation centers.
Incident 6: Chief cook of a merchant vessel gets suffocated
The morning after taking three months’ provisions aboard the vessel, the chief cook of a merchant vessel proceeded to fetch some meat from the refrigerated meat room. Upon opening the door, he was affected by the atmosphere of the meat room. His eyes and nose were severely irritated by the atmosphere and he immediately closed the door. The chief cook reported a ‘smell’ in the meat room to an officer who he encountered in the duty mess room. This officer subsequently entered the meat room to check for problems. After a period of 30 to 60 seconds, he started to feel light headed and left the room.
Further investigation by ship’s staff revealed the cause to be dry ice that had been packed with ice cream that had been received with the stores on the previous day. The remains of the dry ice were disposed of and the meat room thoroughly ventilated.
As a corrective measure, the following measures were undertaken:
• The company’s response to the incident:
• Publicize the incident to all vessels in its fleet
• Ensure that industry guidance including M Notices and other publications that contain guidance for catering ratings are integrated into or highlighted in the catering ratings’ handbooks.
• Investigate the feasibility of fitting of CO2 alarms to all unventilated rooms where frozen provisions are normally stored.
• Appropriate warning notices to be posted on the doors of rooms where frozen provisions are normally stored.
• Develop guidelines and best practice for the receipt handling and storage of provisions for ships’ staff.
• Contact all approved suppliers to warn them of the dangers of supplying stores to ships with dry ice. All suppliers should be instructed to warn vessels of the presence of dry ice or other hazardous goods packed with stores.
Figure 9: Door Safety in Controlled Atmosphere Containers
Figure 10: Safety Decal
Figure 11: Rear Door Curtain
Due to release of gases from refrigerated products
Cold Rooms, Reefer Containers, Refrigerated Cargo holds on ships are to be treated like enclosed spaces. Fruit cargoes, being live cargoes continue with the respiration process throughout their passage time on board. They consume oxygen in the refrigerated space and liberate carbon-dioxide. To make up for the consumed oxygen, voyage instructions include periodic ventilation of the cargo spaces. On reefer containers, air vents are kept partially open either continuously or periodically throughput the voyage to allow the fruit cargo to breathe. In the newer version of reefer containers, this is achieved automatically (AFAM+). Here, even the information on degree and periodicity of opening of the air vent is fed into the controller as an input instruction along with other instructions like temperature set point, humidity content etc.
There is a category of reefer spaces and containers which maintain oxygen deficient atmospheres within the refrigerated spaces. These are known as controlled atmospheres. For the purpose of prolonging the life of fruit cargo by bringing down the respiration rate, the oxygen content within the refrigerated space is maintained at between 2-4% as compared to 21% in the normal atmosphere.
This is achieved by use of additional special machinery components. The space is filled up with nitrogen which is supplemented by the carbon dioxide gas which is liberated due to respiration of the fruit cargo. Special personal safety precautions have been outlined to be followed before exposing technicians to these spaces. These spaces are to be treated as Enclosed Spaces.
Figure 12: Enclosed Spaces
Figure 13: Controlled Atmosphere Storage Space
Door Safety in Controlled Atmosphere Containers
The doors of these containers are provided with a special safety door lock which permits opening only when the oxygen content is above 20.3% and locks when oxygen content is below 19.8%.
Extra Safety Features in Controlled Atmosphere Containers
They are also provided with extra safety decals and a door curtain which will provide additional protection to the personnel preventing accidental exposure to the Controlled atmosphere inside the container.
Figure 14: Banana Carrier
These spaces are to be treated as Enclosed spaces and all personal safety precautions have to be taken before entering these spaces.
Incident 1: Stowaway found dead inside cargo hold of banana carrier
The dead body of a stowaway was found inside the cargo hold of a reefer vessel when the hatch covers were opened for cargo discharge at the discharge port. The ship was carrying bananas inside the hatch. The stowaway was overcome by the carbon dioxide and other gases liberated by the bananas and lost his life.
Along with carbon dioxide, fruit cargoes also liberate ethylene, the sweet smelling gas. This gas is addictive by nature. It is also present at petrol pumps (gas stations) being present in the atmosphere as it is gets separated out from the gasoline over a period of time. It is a sweet smelling poison and can overpower human beings if present beyond a certain TLV (Threshold Limit Value).
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