What is the acceptable oxygen level standard for work in confined spaces?
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This post was last edited by lyhh9024 on 2010-2-9 at 16:39. Our company’s regulations specify that the acceptable oxygen level for working in confined spaces is between 19.5% and 21%. However, we have encountered a new problem: during maintenance tasks, the measured oxygen level sometimes exceeds 21%, though it generally does not go above 22%. The analysts conclude that such conditions are not satisfactory, and it is not allowed to enter the confined space. It’s quite difficult right now – what exactly is the acceptable standard for oxygen levels in confined spaces? Where are the standards?
Our company’s standard is 19.5% to 23.5%; the oxygen content you mentioned should be within the acceptable range, as the oxygen concentration in the atmosphere is around 21%. Under normal conditions, it is possible for this level to exceed 21%, for example, in areas with good greenery the oxygen concentration can reach 22%
According to Article 5 of the Regulations on Safety Management for Work in Confined Spaces, point 8 of the safety measures for such work requires that sampling and analysis must be comprehensive and representative. When the volume of the confined space is large, samples should be taken from the upper, middle, and lower sections for analysis. Ensure that the concentration of combustible gases and the oxygen level in all areas within the confined space are within acceptable limits (when the lower explosive limit of the combustible gas is greater than 4%, a concentration of no more than 0.5% is considered acceptable). When the lower explosion limit is less than 4%, a tested concentration of no more than 0.2% is considered acceptable ； (The oxygen content of 19.5–23.5 is considered acceptable.) ...................................After the analysis results are obtained, the sample must be retained for at least 4 hours. The temperature in confined spaces should be around normal room temperature; it must be measured again at least every 4 hours during operations. If any parameter fails to meet the requirements, the work must be stopped immediately.
The current U.S. standard has changed to 20–22% of the LEL for flammable/gasolineous gases or vapors – which is equivalent to 0%.
I remember it being that the oxygen concentration in confined spaces should not be lower than 18%
19.5～21%, and 19.5~23.5%. In my opinion, a discount can be applied to the upper limit, but absolutely no discount should be given to the lower limit!
Instruments can also fail or be less accurate at times. It would be more reliable to verify it using small animals as well, such as rabbits, by placing them in a confined space for 15 to 30 minutes. If the rabbit does not die after the specified time, then it should not be a problem for humans to go down and carry out their tasks. This post was last edited by ckwcba on 2008-5-6 19:46]
There still isn’t an exact standard. The \"Safety Regulations for Work in Confined Spaces in Chemical Production Units\" specify a range of 18% to 21%, while 23% is the threshold in oxygen-enriched environments
The poster may refer to AQ3028-2008, Safety Specifications for Confined Space Operations in Chemical Production Units. According to section 4.3.1, the oxygen content should generally be between 18% and 21%; in an oxygen-enriched environment, it should not exceed 23.5%. Let me explain what is meant by an oxygen-enriched environment: here, consideration is given to the process of purging such environments with inert gases. Production experience shows that the amount of inert gas required for this purpose is more than three times the volume of the medium to be purged. Therefore, it is quite difficult to maintain an oxygen content of 18% to 21% in an oxygen-enriched environment. In order to ensure the safety of workers entering confined spaces and taking into account the possibilities related to the conditions under which purification can take place, standards such as those set by DuPont suggest that the oxygen content in an oxygen-enriched environment should not exceed 23.5%.
It’s very similar to the **standard from 2006; I can’t remember exactly, but the oxygen level in confined spaces must be at least 19.5%**.