Requirements for oxygen concentration when working inside a container
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This post was last edited by lincqh on 2011-6-16 at 20:29. Original text: Vessels should be thoroughly vented using powered air movers to ensure an atmosphere not less than 19.5% or greater than 21.5% oxygen before an entry is conducted. Translation: Containers should be thoroughly ventilated using electric blowers to ensure that the oxygen concentration inside them is not lower than 19.5% nor higher than 21.5% before anyone enters them. My question: Why is it stipulated this way? If there’s a concern about oxygen deficiency, wouldn’t it be sufficient to require that the oxygen concentration inside the device be no less than 19.5%? Why say “greater than 21.5%” as well?
The oxygen concentration should be maintained between 18% and 22%. Operating in an environment with a concentration lower than 18% constitutes a hypoxic condition that can easily lead to suffocation. On the other hand, a concentration higher than 22% represents a hyperoxic environment; when the oxygen level in the air exceeds 22%, it increases the likelihood of combustion, and flammable materials will burn more intensely as a result. Blowing pure oxygen into a confined space also creates an oxygen-rich environment. When purging oxygen pipelines, an oxygen-rich environment can also be created if the method is not proper.
Reply to 1# lincqh: The current **specified range is 19.5–23.5%. An oxygen-enriched environment can easily lead to fires; on the other hand, too high an oxygen concentration can cause oxygen poisoning.
A level below 18% indicates working in an oxygen-deficient environment, which can easily lead to suffocation; a level above 22% represents an oxygen-rich environment that can cause oxygen poisoning in humans
Hyperbaric oxygen chambers are suitable for patients with breathing difficulties and are not appropriate for healthy people. This is the result of human evolution; normal people have become accustomed to living in an atmospheric environment with 21% oxygen. For healthy people, breathing pure oxygen has more disadvantages than advantages and is not beneficial for blood supply. All tissues in the body cannot tolerate excessive amounts of oxygen; this is because oxygen can react with unsaturated fatty acids without the need for enzyme catalysis, and it can also destroy the phospholipids that store these acids. Phospholipids are the main components of cellular biomembranes, and this process ultimately leads to cell death – a phenomenon known as lipid peroxidation. Furthermore, oxygen’s damage to cells also lies in its ability to generate free radicals, which can induce cancer. Experiments have shown that the way to destroy cell cultures is by placing them in an environment with supersaturated oxygen. Pure oxygen can reduce the blood supply to the body’s own organs and tissues, as the decrease in carbon dioxide leads to a reduction in vascular pressure. When carbon dioxide is added, the blood vessels begin to dilate, which increases blood flow and allows more oxygen to reach critical areas such as the brain and heart. From the perspective of Earth’s history, human adaptation to the current atmospheric composition is the result of long-term biological evolution. The atmospheric composition on Earth has gone through many stages of change; we are now in the third generation, which has lasted for 300 million years – far longer than human history (2 million years). The first generation of atmosphere dates back to 4.6 billion years ago; it was the primitive atmosphere, the reducing gas present when Earth was first formed, with hydrogen and helium accounting for 90% of its composition ； The second-generation atmosphere existed about 2 billion years ago and was mainly composed of volcanic gases, with water vapor accounting for 80% of it. In the third generation of the atmosphere, after chlorophyll was formed, the air became oxygen-rich. When the oxygen level reached 1%, organisms began to reproduce. There was a phase in which the oxygen content was as high as 60%; however, due to the reproduction of dinosaurs, a large number of plants were destroyed, which led to a decrease in oxygen levels, resulting in the oxygen-rich condition we see today. Among them, nitrogen acts as an inert diluent, regulating the solubility of oxygen in the blood; together with carbon dioxide, it controls the rate of all biochemical reactions involving oxygen. This is the great significance of the stability in the concentrations of various components in the atmosphere.
The European and American standards are 19.5%-21.5%, which is more scientific; China’s standard is 18%-22%. The original poster made a mistake in the English translation; what was said is that it should be no less than 19.5% and no more than 21.5%.