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Diving and ROV
Published in Sukumar Laik, Offshore Petroleum Drilling and Production, 2018
On dry land, the air we breathe consists of approximately 21% oxygen and 78% nitrogen, with 1% of other trace gases. However, it can only be used in diving to a depth of around 40 m, after which nitrogen narcosis can occur, which can obviously become very dangerous in a working environment. So, breathing gas mixtures such as Heliox (hydrogen and oxygen) and Trimix (oxygen, nitrogen and helium) are mixed onboard the ship by the life support technicians (LSTs) and used by the divers for breathing. These mixtures are prepared to avoid the risks of nitrogen narcosis and oxygen toxicity. The gases need to be blended at specific ratios, depending on the working depth of the divers.
Ground improvement techniques and lining systems
Published in David Chapman, Nicole Metje, Alfred Stärk, Introduction to Tunnel Construction, 2017
David Chapman, Nicole Metje, Alfred Stärk
Mixed gases are often used to improve the working environment under elevated pressures compared to compressed air. Mixed gases include Heliox, a mixture of helium and oxygen, and Trimix, a mixture of oxygen, nitrogen and helium (Smith 2011b). However, there are limits on exposure time for working in such elevated pressure environments and decompression times also need to be considered, which can severely limit productivity at higher pressures. Therefore, for higher pressures, for example, above 6 or 7 bar, or when long periods of productive work are required, saturation working can be considered. This is where the workers live in a high-pressure environment for extended periods on the surface and are transported under high pressure to the air lock on the TBM. The maximum period for working under these conditions is considered to be 28 days due to psychological problems (Smith 2011b).
Fluidic and thermal properties of heliox enable the efficient generation and delivery of high concentrations of solid-phase, fine particle aerosols from viscous liquids
Published in Aerosol Science and Technology, 2019
Xin Heng, Jinghai Yi, Donovan B. Yeates
Heliox is a mixture of the inert gas, helium, together with oxygen. Unless otherwise denoted, reference to heliox herein refers to 80% helium and 20% oxygen which is widely used. Other mixtures containing higher percentages of oxygen, i.e., 70% helium and 30% oxygen, are available. Heliox’s physical properties lead to potential physiological and clinical advantages for the delivery of aerosols to the lungs (Corcoran and Gamard 2004). The use of heliox in patients has not been uniformly supportive of its clinical utility, however, there is considerable evidence its use can result in clinical improvements in respiratory function and improved delivery of aerosols to the lungs, especially in children and patients with compromised lung function (Katz et al. 2014). Consistent with the lower Reynolds number of heliox compared to air in conducting airways, the decrease in turbulence enables increased aerosol penetration through these airways with a consequential increase in the deposition of aerosols in the peripheral lung, especially in persons with lung disease (Svartengren et al. 1989; Anderson et al. 1993; Goode et al. 2001; Peterson et al. 2008). Compared to air, heliox shows better penetration into constricted airways to improve gas exchange (Jaber et al. 2000). Due to lower molecular weight and consequent low-density and higher diffusion coefficient of heliox, its use results in decreased CO2 retention and thus a reduction in respiratory acidosis (Gluck, Onorato, and Castriotta 1990). The properties of heliox also increase lung compliance and reduce the work of breathing (Beurskens et al. 2015). The use of heliox also has been shown to be associated with reduced inflammation (Yilmaz et al. 2013; Nawab et al. 2005). Additionally, noninvasive ventilation with heliox has been reported to decrease the incidence of intubation in preterm infants suffering from RDS (Long et al. 2016).