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    Oxygen Levels Skuld

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    RAHUL SINGH
    The document discusses oxygen levels in air that are safe and unsafe for human life. It notes that the standard composition of air is approximately 20.9% oxygen but the percentage required varies with pressure. The US OSHA defines oxygen deficiency as less than 19.5% but this does not mean 19.5% is safe, as replacing oxygen with another gas can be toxic. Effects range from impaired coordination at 15-19% oxygen to coma in 40 seconds at 4-6% oxygen.

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    Oxygen Levels Skuld

    Uploaded by

    RAHUL SINGH
    29 views2 pages
    The document discusses oxygen levels in air that are safe and unsafe for human life. It notes that the standard composition of air is approximately 20.9% oxygen but the percentage required varies with pressure. The US OSHA defines oxygen deficiency as less than 19.5% but this does not mean 19.5% is safe, as replacing oxygen with another gas can be toxic. Effects range from impaired coordination at 15-19% oxygen to coma in 40 seconds at 4-6% oxygen.

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    The document discusses oxygen levels in air that are safe and unsafe for human life. It notes that the standard composition of air is approximately 20.9% oxygen but the percentage required varies with pressure. The US OSHA defines oxygen deficiency as less than 19.5% but this does not mean 19.5% is safe, as replacing oxygen with another gas can be toxic. Effects range from impaired coordination at 15-19% oxygen to coma in 40 seconds at 4-6% oxygen.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    29 views2 pages

    Oxygen Levels Skuld

    Uploaded by

    RAHUL SINGH
    The document discusses oxygen levels in air that are safe and unsafe for human life. It notes that the standard composition of air is approximately 20.9% oxygen but the percentage required varies with pressure. The US OSHA defines oxygen deficiency as less than 19.5% but this does not mean 19.5% is safe, as replacing oxygen with another gas can be toxic. Effects range from impaired coordination at 15-19% oxygen to coma in 40 seconds at 4-6% oxygen.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 2

    Hannaford Forensic Services (Asia) Limited

    ‘Safe’ oxygen levels – a short discussion


    At standard atmospheric pressure and temperature, dry air, by volume is
    approximately composed of:

    Nitrogen 78.1%
    Oxygen 20.9%
    Argon 0.9%
    Other 0.1%

    Whilst the composition of air is considered to be fairly consistent, the percentage of


    oxygen required to support life is dependent on pressure as this leads to changes in
    the partial pressure of the gases. At high altitude the partial pressure of oxygen in
    air becomes low such that it cannot support life (for example on Mount Everest).
    However, underwater the partial pressure increases and below 60 metres depth
    oxygen starts to becomes toxic. As such, any discussion on the minimum
    concentration of oxygen required will generally refer to altitude or depth. For the
    purposes of this discussion, it is assumed that work is being undertaken on ships
    and as such relates to air at sea level.

    The United States Department of Labour, Occupational Safety & Health


    Administration (OSHA) document 29 CFR 1910.146(c) defines oxygen deficiency as
    ‘A concentration of oxygen in the atmosphere equal to or less than 19.5% by
    volume’. However, it should be noted that this DOES NOT mean that an
    atmosphere with 19.5% oxygen is safe to enter, it ONLY means that below this level
    it is not considered safe to enter based on the oxygen concentration. If an

    Hannaford Forensic Services (Asia) Limited


    1001, Wayson Commercial Building
    28 Connaught Road West, Sheung Wan, Hong Kong
    Telephone: +852 2548 0577 | Fax: +852 2548 0588 | email: hongkong@hfs-asia.com | www.hfs-asia.com
    Hannaford Forensic Services (Asia) Limited

    atmosphere contains 19.5% oxygen, then 1.4% of another gas has replaced it and
    the atmosphere is potentially deadly1. For reference if this other gas was carbon
    monoxide, unconsciousness would occur within 2 -3 breaths, and death within 3
    minutes. As such, the discussion below relating to the minimum oxygen levels to
    support human life assumes that the air has been analysed for any potential toxic or
    flammable gases.

    The effects of low oxygen atmospheres are summarised in the table below
    (information from OSHA):
    Oxygen percentage in air 2 Effect

    19.5 % Minimum acceptable oxygen level

    15 - 19% Decreased ability to work strenuously May


    impair coordination and may induce early
    symptoms with individuals that have
    coronary, pulmonary, or circulatory problems

    12-14% Respiration and pulse increase; impaired


    coordination, perception, and judgment
    occurs

    10-12% Respiration further increases in rate and


    depth; poor judgment and bluish lips occur

    8-10% Symptoms include mental failure, fainting,


    unconsciousness, an ash-coloured-face,
    blue lips, nausea, and vomiting

    6-8% 8 minutes -100% fatal


    6 minutes - 50% fatal
    4-5 minutes - possible recovery

    4-6% Coma in 40 seconds, convulsions,


    respiration ceases - death

    Dr John Allum

    1
    If the oxygen has been replaced by an inert gas, then the nitrogen content will also have been
    reduced. As such, if the oxygen is reduced to19.5% then the nitrogen will be reduced by 5.2%,
    meaning that the ‘other’ gas will be approximately 6.6% by volume.
    2
    This assumes that the oxygen has been replaced by an inert gas such as nitrogen.

    Page 2 of 2

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