Smoke is the collection of airborne solid and liquid particulates and gases[1] emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires (including stoves, candles, oil lamps, and fireplaces), but may also be used for pest control (cf. fumigation), communication (smoke signals), defense (smoke-screen) or smoking (tobacco, marijuana, etc.) or other inhalation:such as electronic cigarette(ruyan). Smoke is used in rituals, when incense, sage, or resin are burned to produce a smell for spiritual purposes. Smoke is sometimes used as a flavouring agent and preservative for various foodstuffs. Smoke is also sometimes a component of internal combustion engine exhaust gas, particularly diesel exhaust.
Smoke inhalation is the primary cause of death in victims of indoor fires. The smoke kills by a combination of thermal damage, poisoning and pulmonary irritation caused by carbon monoxide, hydrogen cyanide and other combustion products.
Smoke particles are an aerosol (or mist) of solid particles and liquid droplets that are close to the ideal range of sizes for Mie scattering of visible light. This effect has been likened to three-dimensional textured privacy glass[citation needed] — a smoke cloud does not obstruct an image, but thoroughly scrambles it.
Dangers of smoke
Smoke from oxygen-deprived fires contains a significant concentration of compounds that are flammable. A cloud of smoke, in contact with atmospheric oxygen, therefore has the potential of being ignited - either by another open flame in the area, or by its own temperature. This leads to effects like backdraft and flashover.
Many compounds of smoke from fires are highly toxic and/or irritating. The most dangerous is the carbon monoxide, leading to carbon monoxide poisoning, sometimes with supporting effects of hydrogen cyanide and phosgene. Smoke inhalation can therefore quickly lead to incapacitation and loss of consciousness.
Smoke can obscure visibility, impeding occupant exiting from fire areas. In fact, the poor visibility due to the smoke that was in the Worcester Cold Storage Warehouse fire in Worcester, Massachusetts was the exact reason why the trapped rescue firefighters couldn't evacuate the building in time. Due to the striking similarity that each floor shared, the dense smoke caused the firefighters to become disoriented.[2
Visible and invisible particles of combustion
Depending on particle size, smoke can be visible or invisible to the naked eye. This is best illustrated when toasting bread in a toaster. As the bread heats up, the products of combustion increase in size. The particles produced initially are invisible but become visible if the toast is burnt.
Smoke from a typical house fire contains hundreds of different chemicals and fumes. As a result, the damage caused by the smoke can often exceed that caused by the actual heat of the fire. In addition to the physical damage caused by the smoke of a fire - which manifests itself in the form of stains - is the often even harder to eliminate problem of a smokey odor. Just as there are contractors that specialize in rebuilding/repairing homes that have been damaged by fire and smoke, Fabric Restoration companies specialize in restoring fabrics that have been damaged in a fire.
Medicinal Smoke
Throughout recorded history, humans have used the smoke of medicinal plants to cure illness. A sculpture from Persepolis shows Darius the Great (522–486 b.c.), the king of Persia, with two censers in front of him for burning Peganum harmala and/or sandalwood Santalum album, which was believed to protect the king from evil and disease. More than 300 plant species in 5 continents are used in smoke form for different diseases. As a method of drug administration, smoking is important as it is a simple, inexpensive, but very effective method of extracting particles containing active agents. More importantly, generating smoke reduces the particle size to a microscopic scale thereby increasing the absorption of its active chemical principles. However, the hazards of inhaling a particulate are unacceptable to some people. Although the use of cannabis for medicinal purposes has been recorded for centuries, it has only recently become a subject of intense public scrutiny. So far, only a few examples of medicinal smoke have been studied in detail (e.g. cannabis). Smoke-based medicinal substances represent multiple opportunities for studies on the chemical constituents, applications, and introduction and preparation of new drugs and dosage forms.[3]
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