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Compressed Air Work
Work in compressed air, compressed air work or hyperbaric work is occupational activity in an enclosed atmosphere at a controlled ambient pressure significantly higher than the adjacent normal atmospheric pressure. There are many parallels with underwater diving, and a few significant differences. Applications Compressed air work is mostly used in civil engineering projects where a raised ambient pressure is used to counteract ingress of groundwater from the surrounding soil or rock by balancing the hydrostatic pressure of the water with an applied air pressure inside an enclosed and sealed working area, such as a Caisson (engineering), caisson, Shaft (civil engineering), shaft, or tunnel. Classes Traditionally, compressed air work was limited to maximum ambient pressures of between , but experience with offshore saturation diving shows that higher pressures can be managed at acceptable risk using the techniques developed in that industry, including saturation exposures and the us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ambient Pressure
The ambient pressure on an object is the pressure of the surrounding medium, such as a gas or liquid, in contact with the object. Atmosphere Within the atmosphere, the ambient pressure decreases as elevation increases. By measuring ambient atmospheric pressure, a pilot may determine altitude (see pitot-static system). Near sea level, a change in ambient pressure of 1 millibar is taken to represent a change in height of . Underwater The ambient pressure in water with a free surface is a combination of the hydrostatic pressure due to the weight of the water column and the atmospheric pressure on the free surface. This increases approximately linearly with depth. Since water is much denser than air, much greater changes in ambient pressure can be experienced under water. Each of depth adds another bar (unit) , bar to the ambient pressure. Ambient-pressure diving is underwater diving exposed to the water pressure at depth, rather than in a pressure-excluding atmospheric diving suit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blackpool Decompression Tables
Henry Valence "Val" Hempleman (25 March 1922 - 14 July 2006) was a researcher in the field of diving decompression.Originally published in the "Daily Telegraph" 30 Oct 2006 Early life Val Hempleman was the son of Harry Hempleman, a sea captain on the UK-New Zealand route. He was born in at Neasham, Darlington and moved to Hull as a boy. He won a scholarship to Hymers College, Hull, followed by St Catharine's College, Cambridge, where he studied inorganic chemistry and physics. This was interrupted by the Second World War, and he was called up to the Royal Navy and became a research assistant at the physiological laboratory ''Vernon II'' at HMS ''Dolphin'' in Gosport, where he was involved in experimental work assessing the effects of explosions on immersed personnel. After the war he continued his studies, and received an honours degree in chemistry. In 1946 he was employed at the Wellcome Physiological Research Laboratory in Beckham, Kent, where he worked on chemotherapeutic agen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barotrauma
Barotrauma is physical damage to body tissues caused by a difference in pressure between a gas space inside, or in contact with, the body and the surrounding gas or liquid. The initial damage is usually due to over-stretching the tissues in tension or shear, either directly by an expansion of the gas in the closed space or by pressure difference hydrostatically transmitted through the tissue. Tissue rupture may be complicated by the introduction of gas into the local tissue or circulation through the initial trauma site, which can cause blockage of circulation at distant sites or interfere with the normal function of an organ by its presence. The term is usually applied when the gas volume involved already exists prior to decompression. Barotrauma can occur during both compression and decompression events. Barotrauma generally manifests as sinus or middle ear effects, lung overpressure injuries and injuries resulting from external squeezes. Decompression sickness is indir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decompression Sickness
Decompression sickness (DCS; also called divers' disease, the bends, aerobullosis, and caisson disease) is a medical condition caused by dissolved gases emerging from Solution (chemistry), solution as bubbles inside the body tissues during Decompression (diving), decompression. DCS most commonly occurs during or soon after a decompression ascent from underwater diving, but can also result from other causes of depressurisation, such as emerging from a Caisson (engineering), caisson, decompression from Saturation diving, saturation, flying in an Cabin pressurization, unpressurised aircraft at high altitude, and extravehicular activity from spacecraft. DCS and Air embolism, arterial gas embolism are collectively referred to as decompression illness. Since bubbles can form in or migrate to any part of the body, DCS can produce many symptoms, and its effects may vary from joint pain and rashes to paralysis and death. DCS often causes air bubbles to settle in major joints like knee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medical Surveillance
Workplace health surveillance or occupational health surveillance (U.S.) is the ongoing systematic collection, analysis, and dissemination of exposure and health data on groups of workers. The Joint ILO/WHO Committee on Occupational Health at its 12th Session in 1995 defined an occupational health surveillance system as "a system which includes a functional capacity for data collection, analysis and dissemination linked to occupational health programmes". The concept is new to occupational health and is frequently confused with medical screening. Health screening refers to the early detection and treatment of diseases associated with particular occupations, while workplace health surveillance refers to the removal of the causative factors. Aspects Medical surveillance The mission of a medical surveillance program is to keep workers healthy and ensure that employers are meeting OSHA standards in health and safety. Medical surveillance has an emphasis on prevention: it is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medical Fitness To Dive
Fitness to dive (more specifically medical fitness to dive) refers to the medical and physical suitability of a diver to function safely in an underwater environment using diving equipment and related procedures. Depending on the circumstances, it may be established with a signed statement by the diver that they do not have any of the listed disqualifying conditions. The diver must be able to fulfill the ordinary physical requirements of diving as per the detailed medical examination by a physician registered as a medical examiner of divers following a procedural checklist. A legal document of fitness to dive issued by the medical examiner is also necessary. The most important medical is the one before starting diving, as the diver can be screened to prevent exposure in the event of an imminent danger. The other important medicals are after some significant illness, where medical intervention is needed and has to be done by a doctor proficient in diving medicine, and can not be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accelerated Decompression
To prevent or minimize decompression sickness, divers must properly plan and monitor decompression. Divers follow a decompression model to safely allow the release of excess inert gases dissolved in their body tissues, which accumulated as a result of breathing at ambient pressures greater than surface atmospheric pressure. Decompression models take into account variables such as depth and time of dive, breathing gasses, altitude, and equipment to develop appropriate procedures for safe ascent. Decompression may be continuous or staged, where the ascent is interrupted by stops at regular depth intervals, but the entire ascent is part of the decompression, and ascent rate can be critical to harmless elimination of inert gas. What is commonly known as no-decompression diving, or more accurately no-stop decompression, relies on limiting ascent rate for avoidance of excessive bubble formation. Staged decompression may include deep stops depending on the theoretical model used fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Breathing Gas
A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration. Air is the most common and only natural breathing gas, but other mixtures of gases, or pure oxygen, are also used in breathing equipment and enclosed habitats. Oxygen is the essential component for any breathing gas. Breathing gases for hyperbaric use have been developed to improve on the performance of ordinary air by reducing the risk of decompression sickness, reducing the duration of decompression, reducing nitrogen narcosis or reducing work of breathing and allowing safer deep diving. Description A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration. Air is the most common and only natural breathing gas. Other mixtures of gases, or pure oxygen, are also used in breathing equipment and enclosed habitats such as scuba equipment, surface supplied diving equipment, recompression chambers, high-altitude mountaineering, high-flying aircraf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Airlock
An airlock is a room or compartment which permits passage between environments of differing atmospheric pressure or composition, while minimizing the changing of pressure or composition between the differing environments. An airlock consists of a chamber with two Hermetic seal, airtight doors or openings, usually arranged in series, which do not open simultaneously. Airlocks can be small-scale mechanisms, such as Fermentation lock, those used in fermenting, or larger mechanisms, which often take the form of an antechamber. An airlock may also be used underwater to allow passage between the air environment in a pressure vessel, such as a submarine, and the water environment outside. In such cases the airlock can contain either Atmosphere of Earth, air or water. This is called a floodable airlock or underwater airlock, and is used to prevent water from entering a submersible vessel or underwater habitat. Operation The procedure of entering an airlock from the external or am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Personal Protective Equipment
Personal protective equipment (PPE) is protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards addressed by protective equipment include physical, electrical, heat, chemical, biohazards, and airborne particulate matter. Protective equipment may be worn for job-related occupational safety and health purposes, as well as for sports and other recreational activities. ''Protective clothing'' is applied to traditional categories of clothing, and ''protective gear'' applies to items such as pads, guards, shields, or masks, and others. PPE suits can be similar in appearance to a cleanroom suit. The purpose of personal protective equipment is to reduce employee exposure to hazards when engineering controls and administrative controls are not feasible or effective to reduce these risks to acceptable levels. PPE is needed when there are hazards present. PPE has the serious limitation that it d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trimix (breathing Gas)
Trimix is a breathing gas consisting of oxygen, helium, and nitrogen. It is used in deep commercial diving, during the deep phase of dives carried out using technical diving techniques, and in advanced recreational diving. The helium is included as a substitute for some of the nitrogen, to reduce the narcotic effect of the breathing gas at depth and to reduce the work of breathing. With a mixture of three gases it is possible to create mixes suitable for different depths or purposes by adjusting the proportions of each gas. Oxygen content can be optimised for the depth to limit the risk of toxicity, and the inert component balanced between nitrogen (which is cheap but narcotic) and helium (which is not narcotic and reduces work of breathing, but is more expensive and can increase heat loss). The mixture of helium and oxygen with a 0% nitrogen content is generally known as heliox. This is frequently used as a breathing gas in deep commercial diving operations, where it is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osteonecrosis
Avascular necrosis (AVN), also called osteonecrosis or bone infarction, is death of bone tissue due to interruption of the blood supply. Early on, there may be no symptoms. Gradually joint pain may develop, which may limit the person's ability to move. Complications may include collapse of the bone or nearby joint surface. Risk factors include bone fractures, joint dislocations, alcoholism, and the use of high-dose steroids. The condition may also occur without any clear reason. The most commonly affected bone is the femur (thigh bone). Other relatively common sites include the upper arm bone, knee, shoulder, and ankle. Diagnosis is typically by medical imaging such as X-ray, CT scan, or MRI. Rarely biopsy may be used. Treatments may include medication, not walking on the affected leg, stretching, and surgery. Most of the time surgery is eventually required and may include core decompression, osteotomy, bone grafts, or joint replacement. About 15,000 cases occur pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
