The sport of skiing definition equipment basic skills and dangers

Shortly after arriving on scene, Portland State University Police Department Officers requested assistance from Portland Police Bureau Central Precinct Officers who were also responding to the calls, but had not yet arrived on scene. Based on the subject's behavior, a Portland Police Bureau member requested emergency medical personnel respond to the location to transport the subject by ambulance to an area hospital for treatment of an unidentified medical condition. After arriving at the hospital, medical personnel determined the subject was deceased.

The sport of skiing definition equipment basic skills and dangers

Rebreather Less common are closed circuit CCR and semi-closed SCR rebreathers which, unlike open-circuit sets that vent off all exhaled gases, process all or part of each exhaled breath for re-use by removing the carbon dioxide and replacing the oxygen used by the diver.

Rebreathers are more complex and more expensive than open-circuit scuba, and special training and correct maintenance are required for them to be safely used, due to the larger variety of potential failure modes.

Minimising the inert gas loading of the diver's tissues for a given dive profile reduces the decompression obligation. This requires continuous monitoring of actual partial pressures with time and for maximum effectiveness requires real-time computer processing by the diver's decompression computer.

Decompression can be much reduced compared to fixed ratio gas mixes used in other scuba systems and, as a result, divers can stay down longer or require less time to decompress. Planning decompression requirements requires a more conservative approach for a SCR than for a CCR, but decompression computers with a real time oxygen partial pressure input can optimise decompression for these systems.

Because rebreathers produce very few bubbles, they do not disturb marine life or make a diver's presence known at the surface; this is useful for underwater photography, and for covert work.

The reduced nitrogen may also allow for no stops or shorter decompression stop times or a shorter surface interval between dives. A common misconception is that nitrox can reduce narcosisbut research has shown that oxygen is also narcotic.

To displace nitrogen without the increased oxygen concentration, other diluent gases can be used, usually heliumwhen the resultant three gas mixture is called trimixand when the nitrogen is fully substituted by helium, heliox. These different gas mixtures may be used to extend bottom time, reduce inert gas narcotic effects, and reduce decompression times.

Personal mobility is enhanced by swimfins and optionally diver propulsion vehicles. Fins have a large blade area and use the more powerful leg muscles, so are much more efficient for propulsion and manoeuvering thrust than arm and hand movements, but require skill to provide fine control.

Several types of fin are available, some of which may be more suited for manoeuvering, alternative kick styles, speed, endurance, reduced effort or ruggedness. Balanced trim which allows the diver to align in any desired direction also improves streamlining by presenting the smallest section area to the direction of movement and allowing propulsion thrust to be used more efficiently.

The sport of skiing definition equipment basic skills and dangers

The depth is usually controlled by the diver by using diving planes or by tilting the whole sled. Buoyancy compensatorDiving weighting systemand Diver trim Diver under the Salt Pier in Bonaire To dive safely, divers must control their rate of descent and ascent in the water [2] and be able to maintain a constant depth in midwater.

Equipment such as diving weighting systemsdiving suits wet, dry or semi-dry suits are used depending on the water temperature and buoyancy compensators can be used to adjust the overall buoyancy.

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This minimises the effort of swimming to maintain depth and therefore reduces gas consumption. The buoyancy of any object immersed in water is also affected by the density of the water.

Diving in different environments also necessitates adjustments in the amount of weight carried to achieve neutral buoyancy. The diver can inject air into dry suits to counteract the compression effect and squeeze.

Buoyancy compensators allow easy and fine adjustments in the diver's overall volume and therefore buoyancy. It is changed by small differences in ambient pressure caused by a change in depth, and the change has a positive feedback effect. A small descent will increase the pressure, which will compress the gas filled spaces and reduce the total volume of diver and equipment.

This will further reduce the buoyancy, and unless counteracted, will result in sinking more rapidly. The equivalent effect applies to a small ascent, which will trigger an increased buoyancy and will result in accelerated ascent unless counteracted. The diver must continuously adjust buoyancy or depth in order to remain neutral.

Fine control of buoyancy can be achieved by controlling the average lung volume in open circuit scuba, but this feature is not available to the closed circuit rebreather diver, as exhaled gas remains in the breathing loop. This is a skill which improves with practice until it becomes second nature.

Minimising the volume of gas required in the buoyancy compensator will minimise the buoyancy fluctuations with changes in depth.

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This can be achieved by accurate selection of ballast weight, which should be the minimum to allow neutral buoyancy with depleted gas supplies at the end of the dive unless there is an operational requirement for greater negative buoyancy during the dive. Recreational divers who do not incur decompression obligations can get away with imperfect buoyancy control, but when long decompression stops at specific depths are required, the risk of decompression sickness is increased by depth variations while at a stop.

Decompression stops are typically done when the breathing gas in the cylinders has been largely used up, and the reduction in weight of the cylinders increases the buoyancy of the diver.

Enough weight must be carried to allow the diver to decompress at the end of the dive with nearly empty cylinders. Underwater vision A diver wearing an Ocean Reef full face mask Water has a higher refractive index than air — similar to that of the cornea of the eye. Light entering the cornea from water is hardly refracted at all, leaving only the eye's crystalline lens to focus light.

This leads to very severe hypermetropia. People with severe myopiatherefore, can see better underwater without a mask than normal-sighted people.

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The faceplate of the mask is supported by a frame and skirt, which are opaque or translucent, therefore total field-of-view is significantly reduced and eye—hand coordination must be adjusted.

Generic corrective lenses are available off the shelf for some two-window masks, and custom lenses can be bonded onto masks that have a single front window or two windows. Swimming goggles are not suitable for diving because they only cover the eyes and thus do not allow for equalisation.

Failure to equalise the pressure inside the mask may lead to a form of barotrauma known as mask squeeze. To prevent fogging many divers spit into the dry mask before use, spread the saliva around the inside of the glass and rinse it out with a little water.

The saliva residue allows condensation to wet the glass and form a continuous film, rather than tiny droplets.Its easy to write about what the government or other people should do with our/their money.

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The sport of skiing definition equipment basic skills and dangers

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