• Cooling India
  • Feb 15, 2018

Low Temperature Hazards
in Refrigeration

Human beings’ exposure to low temperatures can cause certain serious physiological disabilities. In this article, we examine the various low temperature hazards in refrigerated spaces and the cold atmospheres…

- C Maheshwar


 Refrigeration involves creation of low temperatures in spaces. Human beings’ exposure to low temperatures can cause certain serious physiological disabilities. Human beings are basically warm blooded animals. The blood circulation keeps the body temperatures within very close limits by rejecting the extra heat generated in the body due to calorie intake in the food. Exposure to low temperatures can cause of excessive loss of body heat and also can cause local damage to the tissues of the exposed skin. In this article, we examine the various low temperature hazards in refrigerated spaces and the cold atmospheres.

  The following are the various low temperature hazards of exposure to cold temperatures:

• Frost Bite
• Cold Burns
• Hypothermia
• Cold Shock

FROST BITE

What is Frostbite?

  Frostbite is the most serious cold weather injury of the foot, as it involves the freezing of body tissue, vascular damage, metabolic changes, and even tissue death. Superficial frostbite injuries involve surface-level skin, while more serious injuries can affect the muscles, tendons, nerves, and bone. The worst cases involve prolonged exposure to the elements, a slow freeze, and an even slower re-warming process.

  Frostbite should be treated in a medical facility. There, the affected area can be re-warmed with heated wet packs and a tub of 104 to 108°C degree water. Pain relievers can also be administered during this process. Once warmed, the affected area can be dressed and splinted. Sometimes blisters and infections require further topical treatment.

  Even with proper treatment, it could take 1-3 months to recover. In some instances, the tissue damage is so severe that patients require debridement, skin grafting, or amputation. Some people report persistent issues, such as sensitivity to the cold, burning, tingling, pain, increased sweating, and arthritis.

  Direct exposure of body tissues to refrigerant can cause frostbite. Liquid refrigerant suddenly released from high pressure to atmospheric pressure will flash and boil to vapor. Naturally, the temperature of the refrigerant will drop quickly to the boiling point and the refrigerant will quickly absorb heat from whatever it is touching. If the refrigerant is touching skin, it absorbs body heat from that area and causes local overcooling. This can cause frostbite.

  Frostbite occurs when tissues freeze. This condition happens when you are exposed to temperatures below the freezing point of skin. Hypothermia is the condition of developing an abnormally low body temperature. Frostbite and hypothermia are both cold-related emergencies.

  In Frostbite, nose, cheeks, ears, fingers, and toes (body extremities) are most commonly affected. Everyone is susceptible, even people who have been living in cold climates for most of their lives.

Figure 1: Three Degrees of Frostbite

Risk Factors for Cold Weather Foot Injuries

  Anyone can get a cold weather foot injury, but one may be particularly, susceptible if the following risk factors apply:

  Poor circulation: Conditions like diabetes, cardiovascular disease, and Raynaud’s phenomenon make a person more susceptible to winter foot injuries with a greater propensity for blood vessel constriction and inadequate flow to the extremities. Diabetics often suffer from a type of nerve damage called peripheral neuropathy, which makes the feet feel numb.

  Alcohol & tobacco: Alcohol impairs judgment and dilates the blood vessels to increase heat loss throughout the body, so it’s no wonder that it’s commonly associated with overexposure. Tobacco alters blood flow to the hands and feet especially.

  Inadequate clothing: Proper winter weather clothing insulates the body from cold, allows the evaporation of perspiration, and keeps out wind and wet. Wearing two pairs of socks is ideal — a moisture-wicking cotton blend closest to the skin and warm wool on the outside. Boots should cover the ankles and not be too tight.

  Nutrition: Dehydration, low blood sugar, low body mass index, and poor nutrition can all affect the body’s ability to regulate temperature.

  Moisture: Excessive sweat or dampness significantly increases heat loss.

  People at greatest risk for frostbite and hypothermia include people:

• who spend a great deal of time outdoors, such as the homeless, hikers, hunters, etc.;
• under the influence of alcohol;
• who are elderly without adequate heating, food, and shelter;
• who are exhausted or excessively dehydrated;
• who are mentally ill.

Figure 2: Frostbite on Hands

Frostbite Causes

  The body works to stay alive first, and to stay functioning second. In conditions of prolonged cold exposure, the body sends signals to the blood vessels in arms and legs telling them to constrict (narrow). By slowing blood flow to the skin, the body is able to send more blood to the vital organs, supplying them with critical nutrients, while also preventing a further decrease in internal body temperature by exposing less blood to the outside cold.
As this process continues and the extremities (the parts farthest from the heart) become colder and colder, a condition called the hunter’s response is initiated. The blood vessels are dilated (widened) for a period of time and then constricted again. Periods of dilatation are cycled with times of constriction in order to preserve as much function in the extremities as possible. However, when the brain senses that there is a danger of hypothermia (when the body temperature drops significantly below 98.6°F); it permanently constricts these blood vessels in order to prevent them from returning cold blood to the internal organs. When this happens, frostbite has begun.

  Frostbite is caused by two different means: cell death at the time of exposure and further cell deterioration and death because of a lack of oxygen.

Recognizing Frostbite Symptoms

  Initially, ice crystals form in the space outside of the cells. Water is lost from the cell’s interior, and dehydration promotes the destruction of the cell.

  In the second, the damaged lining of the blood vessels is the main culprit. As blood flow returns to the extremities upon rewarming, it finds that the blood vessels themselves are injured, also by the cold. Holes appear in vessel walls and blood leaks out into the tissues. Flow is impeded and turbulent and small clots form in the smallest vessels of the extremities. Because of these blood flow problems, complicated interactions occur, and inflammation causes further tissue damage. This injury is the primary determinant of the amount of tissue damage that occurs in the end.

  It is rare for the inside of the cells themselves to be frozen. This phenomenon is only seen in very rapid freezing injuries, such as those produced by frozen metals.

Preventing Frostbite and Other Cold Weather Foot Injuries

  Frigid temperatures and overexposure to the cold can cause lasting foot problems with injury to the skin and soft tissue. Early signs and symptoms of a cold weather foot condition may include burning, tingling, or changes in skin colour, but often times, the foot simply goes numb–making it even harder to tell how much damage has been done. Cold weather injuries are even possible when temperatures are above freezing, especially when there are high winds or your socks are wet.

  Feet and hands are particularly susceptible to frostbite because the body is busy working hard to keep the internal organs warm.

Figure 3: Frostbite on toes

COLD BURN

What is Cold Burn?

  Cold burn can be described as a kind of skin and tissue damage which happens when the skin comes in contact with some extremely cold objects such as snow, dry ice, liquid nitrogen and helium. Blisters are visible and tendons, muscles, nerves and bones are in a potential danger. In some cases gangrene may occur, and the affected part of the body must be amputated. Feet, nose, ears and hand are most prone to frostbites but generally cold burns can be related to every part of the body. When we try to warm up the affected area, pain will follow and some burning or tingeing sensation. Cold burns will affect anybody spending enough time in the cold, but diabetics, Raynaud phenomenon patients, or takers of beta-blockers are more prone to frostbites.

Figure 4: Cold Burn on hand

Incidents of Cold Burns

Incident 1: Cold Burns during Training

  In one of the training sessions, during the exercise of charging refrigerant, some of the liquid refrigerant droplets fell on the hand of the trainee technician. Immediately, there was a bubble formation underneath the skin, with onset of pain. Luckily, the cold burn injury was mild and the technician recovered with a mild dose of pain killer and superficial ointment. Hence, there is the need for gloves when working on refrigerants and refrigeration equipment.

Incident 2: Cold Burns from Refrigerant hose connections

  Very commonly, there is a chance of refrigerant in the form of liquid or vapour to come out of the system under pressure when the connections are being fitted or being removed. It is always recommended to have control over the hand operated valves. If the connecting pipes are not fitted properly, due to pressure, the connections may come off, ejecting refrigerant under pressure; pipeline itself moving about uncontrollable causing injuries to the personnel around. There are many different forms of connecting devices, the right adapters have to be used. We find that often people are struggling in making the connections.

Figure 5: Manifold Gauge set and hose connections

Incident 3: Cold burns from Domestic Fridge System

  The shipboard domestic refrigeration system – compressor was cutting in and off frequently. There was trouble to maintain the cold room temperatures. Obviously, the Chief Engineer ran around and suspected that the refrigerant return line accumulator filter getting clogged. He instructed the 2/E and 3/E to isolate and clean the filter. The Chief Engineer did mention that he had closed all the valves and sucked the refrigerant from the system. Without cross checking valves or a check for pressure, the second and third engineers slackened the bolts of the accumulator filter.

  To their surprise, there was a sudden explosion (minor explosion) and high-pressure refrigerant gushed out into the atmosphere where the place was restricted. The engineers received cold burns on their hands and shoulders, where the colour of their skin changed immediately. Fortunately, it was very minor and they had a protective eye goggles.

Incident 4: Refrigerant spray on hand Source: MARS 201634

  After provisioning the vegetable room at port, it was observed that the temperature did not drop to its normal operational range. The electrician was detailed to investigate and determine the problem. While he was inspecting the solenoid valve of the refrigeration gas lines using a wrench, refrigerant gas suddenly released and sprayed on his hand. At first, there was no pain and the electrician did not realize the damage done to his hand due to the cold gas. Soon however, a second degree burn with severe pain manifested.

  The company investigation found, among other things, that there had been a failure to complete a permit to work. The permit to work was necessary due to the fact that work was to be done on a line presenting a hazard. This first failure probably contributed to a second dangerous act that of not wearing proper personal protective equipment (PPE), in this case gloves. Also, the normal lock-out/tag-out procedure was not followed as the inlet and outlet valves were not closed prior to the work and pressure was maintained within the lines.

Figure 6: Cold Burn on fingers

Lessons learned

– PPE such as boots, gloves and glasses should be second nature in a truly safety conscious work environment.
– Permits to work are not just a paper exercise, but contain valuable checklists to help crew members stay safe.
– Consulting the Material Safety Data Sheet (MSDS) for the material to be worked on should become second nature.
– While every crew member is responsible for following procedures, safety leadership is also an important element in the system. In this case, both sides of the equation were less than adequate.

Figure 7: Simulation of Refrigerant spray on hand

Hypothermia

What is Hypothermia?

  Hypothermia is a condition in which core temperature drops below that required for normal metabolism and body functions which is defined as 35.0°C (95.0°F). Body temperature is usually maintained near a constant level of 36.5–37.5°C (98–100°F) through biologic homeostasis or thermoregulation. If exposed to cold and the internal mechanisms are unable to replenish the heat that is being lost a drop in core temperature occurs. As body temperature decreases characteristic symptoms occur such as shivering and mental confusion

Figure 8: Stages of Hypothermia

Signs & Symptoms of Hypothermia

  The signs and symptoms vary depending on the degree of hypothermia and may be divided by the three stages of severity.

Mild

  Symptoms of mild hypothermia 32–35°C (90–95°F) are shivering, hypertension and tachycardia. These are all physiological responses to preserve heat. Mental confusion may also be present.

Moderate

  Body temperature of 28–32°C (82–90°F) results in shivering becoming more violent. Muscle mis-coordination becomes apparent. Movements are slow and labored, accompanied by a stumbling pace and mild confusion, although the victim may appear alert. Surface blood vessels contract further as the body focuses its remaining resources on keeping the vital organs warm. The victim becomes pale. Lips, ears, fingers and toes may become blue.

Severe

  Body temperature drops below approximately 28°C (82°F) shivering stops. Difficulty in speaking, sluggish thinking, and amnesia start to appear; inability to use hands and stumbling is also usually present. Cellular metabolic processes shut down. Below 30°C (86°F), the exposed skin becomes blue and puffy, muscle coordination becomes very poor, walking becomes almost impossible, and the victim exhibits incoherent/irrational behavior including terminal burrowing or even a stupor. Pulse and respiration rates decrease significantly, but fast heart rates can occur. Major organs fail. Clinical death occurs. Because of decreased cellular activity in stage 3 hypothermia, the body will actually take longer to undergo brain death.

  As the temperature decreases further physiological systems falter and heart rate, respiratory rate, and blood pressure all decreases. This results in an expected HR in the 30s with a temperature of 28°C (82°F).

Skin Conditions

  A number of skin conditions may be associated with hypothermia or may occur with normal body temperature. These include: cryopedis and frostbite.

Paradoxical Undressing

  Twenty to fifty percent of hypothermia deaths are associated with paradoxical undressing. This typically occurs during moderate to severe hypothermia, as the person becomes disoriented, confused, and combative. They may begin discarding their clothing, which, in turn, increases the rate of heat loss. One explanation for the effect is a cold-induced malfunction of the hypothalamus, the part of the brain that regulates body temperature. Another explanation is that the muscles contracting peripheral blood vessels become exhausted (known as a loss of vasomotor tone) and relax, leading to a sudden surge of blood (and heat) to the extremities, fooling the person into feeling overheated.

Terminal Burrowing

  In the final stages of hypothermia, the brain stem produces a burrowing-like behavior. Similar to hibernation behavior in animals, individuals with severe hypothermia are often found in small, enclosed spaces, such as under the bed or behind wardrobes.

Causes of Hypothermia

Hypothermia usually occurs from exposure to low temperatures and is frequently complicated by alcohol. Any condition which decreases heat production, increases heat loss, or impairs thermoregulation, however, may contribute. Thus, risk including: any condition that affects judgment (hypoglycemia), the extremes of age, male gender, poor clothing, chronic medical conditions (such as hypothyroidism and sepsis), substance abuse, homelessness, and living in a cold environment. It occurs frequently in major trauma.

Alcohol

  Alcohol consumption increases the risk of hypothermic via its action as a vasodilator. It increases blood flow to the body’s extremities, making a person feel warm, while increasing heat loss Between 33 to 73% of cases of hypothermia are complicated by alcohol.

Figure 9: Progressive Phases of Hypothermia

Water

  Hypothermia continues to be a major limitation to diving in cold water. The limitation of finger dexterity due to pain or numbness decreases general safety and work capacity, which consequently increases the risk of other injuries. Pressurized heliox breathing mixtures have a much higher thermal mass than air, so for diving below 100 meters, not only is a hot water suit required, but the breathing mixture must be pre-heated, or the symptoms of hypothermia can set in without realization and cause death in minutes.

  Other predisposing factors leading to immersion hypothermia include dehydration, inadequate rewarming with repetitive diving, starting while wearing cold, wet dry suit undergarments, sweating with work, inadequate thermal insulation (for example, thin dry suit undergarment), lack of heated breathing gas with deep heliox diving, and poor physical conditioning.

  Heat is lost more quickly in water. Water temperatures that would be quite reasonable as outdoor air temperatures can lead to hypothermia. Water temperature of 10°C (50°F) often lead to death in one hour, and water temperatures hovering at freezing can lead to death in as little as 15 minutes. Water at a temperature of 26°C (79°F) may after prolonged exposure lead to hypothermia

Pathophysiology

  Heat is primarily generated in the heart and liver while it is lost through the skin (90%) and lungs (10%). Heat production may be increased 2 to 4 fold through muscle contractions (i.e., exercise and shivering). Rates of heat loss can be affected by clothing and other environmental conditions.

Prevention of Hypothermia

  Appropriate clothing helps to prevent hypothermia. Synthetic and wool fabrics are superior to cotton as they provide better insulation when wet and dry more quickly. Some synthetic fabrics, such as polypropylene and polyester, are used in clothing designed to wick perspiration away from the body, such as liner socks and moisture-wicking undergarments.

50/50/50 rule

  If someone is in 50°F water for 50 minutes, he/she has a 50 percent better chance of survival if wearing a life jacket. The heat escape lessening position can be used to increase survival in cold water.

Miraculous Recoveries!

Incident 1 - Feb 25th, 2001 – Toddler comes back to life after she wandered outside in bone-numbing weather

  In Edmonton, Canada, a doctor who helped bring a toddler back to life after she wandered outside in bone-numbing weather says there was a magical element to the girl’s recovery. Dr Allan De Caen recalled how a medical team at the Stollery Children’s Hospital went into action to revive the 13-month-old whose heart had stopped for two hours.

  A toddler who wandered outside in her diaper in sub-zero weather and was found virtually frozen face down in the snow appears to have survived the ordeal without brain damage.
As the child arrived by ambulance, the team began setting up a heart and lung machine - to help warm her body. But before they could start running the machine, the baby’s heart started beating on its own. The pediatric intensive care specialist said “Sometimes it takes something beyond just the personnel and the equipment, I don’t know whether you talk about it as a greater being or whatever your personal beliefs are, clearly something or someone was on this little girl’s side.”

  She was looking around her hospital room and smiling. He said her frostbite injuries are extensive and it will take weeks or months before doctors know what the outcome of those will be. Her brain function appears to be normal, although it will require close monitoring as she grows up, he added.

  No one knows how long she had been outside in the -20°C weather clad only in her diaper.
Her mother woke up about 3 a.m. Saturday and realized the girl was not in bed with her. She found the baby curled up in the snow in the backyard. The mom and little girl had slept that night at a friend’s house. The child’s toes were frozen together and her mouth was frozen shut. Her body temperature was 16°C instead of the body’s normal temperature of 37°C.
Incident 2 – 3 December 2014 - Toddler recovered in hospital after being found unconscious in freezing temperatures in Poland.

  The two-year-old boy, named in reports as Adam, was discovered lying on the ground in the village of Raclawice, just north of Krakow. He was wearing only pajamas. Doctors said he had been brought out of a medically-induced coma and his health was improving. The boy’s grandmother has said she did not see him leave her home. Police found the boy lying unconscious near a river, after apparently wandering outside several hours earlier. The area’s temperature had fallen to -7°C (19°F) overnight. The boy’s body temperature was 12°C (54°F) when he arrived at Krakow children’s hospital, doctors said, and he was placed in an induced coma. He was blinking and moving his limbs but was still on a respirator, as per Janusz Skalski, a heart surgeon at the children’s hospital in Krakow.

  “We’re very pleased with his condition... there are no negative symptoms, he’s improving.
Hypothermia expert Dr. Tomasz Darocha told that until now, the most dramatic case of recovery from hypothermia involved a Scandinavian woman whose body temperature had dropped to 13.7°C.

Cold Shock

What is Cold Shock?

  Often Cold shock is presented as an afterthought in a discussion on Hypothermia. Actually, Cold Shock occurs before the onset of Hypothermia. It can cause death of a person instantly before hypothermia has a chance to set in. Cold Shock is more immediate. Cold Shock is normally associated with frigid waters; however, a person can also undergo cold shock due to sudden changes in ambient temperatures.

  It is almost instantaneous reaction of the body to immersion in cold water. A variety of symptoms can cause immediate incapacitation or even death. Risk and symptoms of Cold Shock start manifesting when water temperatures are close to 55°F and increase as water temperatures go down. Air temperatures are not relevant. Sudden immersion at these water temperatures can cause uncontrolled gasping which if the head is under water at that time, will lead to nearly instant drowning. This is one reason why kayakers have been found upside down. seemingly never even attempting to roll or wet exit. Cold shock can also play havoc with breathing even if head is above water. It can cause hyperventilation, which can lead to panic and a condition called Alkalosis which can cause confusion, dizziness and possible loss of consciousness before actual hypothermia begins to set in. Some people experience breathlessness or inability to breathe. From here, dizziness, panic and an overwhelming sense of claustrophobia can take hold causing hyperventilation once again. Cold Shock can kill you instantly or slow you down and put you into a state where you will be making bad decisions long before the onset of hypothermia.

  In many maritime disasters, like Titanic, Herald of Free Enterprise and Oceans capsizing accidents, many instantaneous deaths occurred due to cold shock due to the sudden exposure to cold water. Prolonged exposure to cold water caused hypothermia and took toll of many persons. Persons exposed to sub-zero temperatures when carrying frozen cargo can also suffer from cold shock, especially, when it is the first time. By experience, one gets used and is prepared suitably both physically and mentally. It will be a good idea to have a buffer chamber from accommodation to the freezing chambers to prevent sudden change in ambient temperature.

Conditioning against Cold Shock

  It is possible to undergo physiological conditioning to reduce the cold shock response, and some people are naturally better suited to swimming in very cold water. Adaptations include the following:

• Having an insulating layer of body fat covering the limbs and torso without being overweight;
• Ability to experience immersion without involuntary physical shock or mental panic;
• Ability to resist shivering;
• Ability to raise metabolism (and, in some cases, increase blood temperature slightly above the normal level
• Generalised delaying of metabolic shutdown (including slipping into unconsciousness) as central and peripheral body temperatures fall

  In these ways, winter swimmers can survive both the initial shock and prolonged exposure. Nevertheless, the human organism is not suited to freezing water: the struggle to maintain blood temperature (by swimming or conditioned metabolic response) produces great fatigue after thirty minutes or less.

Figure 10: Hypothalamus in Human Brain

Effect of Sudden Change in Temperature

  Sudden change in temperature from extreme hot to cold can have a serious effect on people who have a history of cold-related disorders. Doctors say managers of malls, offices, public buildings, mosques and even hospitals, which sometimes record temperatures as low as 19°C, have a responsibility to ensure that the inside of their establishments is not unhealthy.

  The body undergoes a certain amount of stress when it is forced to go from a boiling hot environment into an air conditioned one. It dries off your skin, the mucus membrane and the eyes. We see patients who say they went to the malls or their offices and it was extremely cold. Eye infections, respiratory infections and muscular spasms are caused by this change in temperature.

  The recommended temperature should be between 23°C and 25°C to prevent susceptibility to ailments. The change in temperature can exacerbate coronary heart diseases, vascular cardiac, vascular brain diseases and peripheral vascular [artery and vein] diseases.
Whenever, anybody has to enter an air-conditioned space from outside hot weather, to prevent cold shock from occurring, the person should pass through one or more series of chambers with progressively reducing temperatures. Similarly, drinking cold water immediately after coming from an outside hot atmosphere should be avoided. Warm water or water at room temperature is recommended.

  It is also recommended during bathing not to expose the head portion of the body to the stream of cold water first. The temperature change should occur gradually from feet upwards. There have been cases of heart attacks and brain hemorrhages attributed to the sudden change of temperature of heart and brain from hot to cold.

Why Cold Shock Occurs?

  The human body does not adapt to sudden changes in temperature. It likes to keep the temperature within very narrow limits. The hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland (hypophysis).

  The hypothalamus is located below the thalamus and is part of the limbic system. In the terminology of neuroanatomy, it forms the ventral part of the diencephalon. All vertebrate brains contain a hypothalamus. In humans, it is the size of an almond.

  The hypothalamus is responsible for the regulation of certain metabolic processes and other activities of the autonomic nervous system. It synthesizes and secretes certain neurohormones, called releasing hormones or hypothalamic hormones, and these in turn stimulate or inhibit the secretion of pituitary hormones. The hypothalamus controls body temperature, hunger, important aspects of parenting and attachment behaviors, thirst, fatigue, sleep, and circadian rhythms.

  In response to the temperature changes, the hypothalamus stimulates vasoconstriction or vasodilation. Vasodilation occurs when there is increase in temperature to send blood to the skin to cool off before returning to the essential organs like brain, heart, lungs etc. to prevent overheating. Vasoconstriction occurs when there is decrease in temperature to prevent cooling off and keeping the warm blood around the essential organs like brain, heart, lungs etc. to prevent overcooling. When people enter hot areas, the body attempts to adapt to the new temperature quickly and vasodilates quickly. The rapid vasodilation causes rapid drop in blood pressure and there is a chance that a person may faint. When a person enters a cold area, sudden chilling causes vasoconstriction. This can cause increased blood pressure followed by pain and heart attack and brain hemorrhages.

What causes cold-water shock?

  Cold water shock is the first stage of the sudden and unexpected immersion in water which temperature is of 15°C or lower and occurs during the first minute of exposure. Cold-water shock likely causes more deaths than hypothermia. Canada’s substantially cold waters are especially dangerous when you fall into them unexpectedly.

Cold Water Shock Symptoms

  The reactions of the body may be muscle spasms and hyperventilation. Other symptoms may be an increase of the pulse and blood pressure. Sudden immersion into cold water may cause cardiac arrest, even for a healthy person. The shock of the cold water can also cause an involuntary gasp reflex that can cause victims to swallow water and drown, even for a good swimmer. Cold water can paralyze the muscles instantly.

Cold water shock treatments

  If you are wearing a lifejacket before falling into cold water, it will keep you afloat while you gain control of your breathing and prevent drowning from loss of muscle control. Trying to grab a lifejacket while in the water, let alone putting one on, will be very hard because of the changes your body will be experiencing. People in cold-water shock should try not to panic and try to control their breathing.


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