Photograph of a Drager hand pump used to measure carbon dioxide levels in the environment. Toxicity of Oxygen Gas Exposure, O2
Poisoning Symptoms, Oxygen Gas Exposure Limits, and Links to Toxic Gas Testing Procedures

  • OXYGEN - O2 HAZARDS - CONTENTS: Recommended limits for oxygen gas exposure or usage. Symptoms & effects of exposure to unusually high levels of oxygen. Recommendations for gas measurement instruments, gas detector tubes, Draeger & Gastec tubes & pumps for detection of gases
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Effects of exposure to abnormal levels of oxygen gas:: This document discusses the toxicity and exposure limits for exposure to oxygen gas O2).

We give references and explanation regarding toxicity of oxygen, based on literature search and obtained from the U.S. government and expert sources. This text may assist readers in understanding these topics. However it should by no means be considered complete nor authoritative. Seek prompt advice from your doctor or health/safety experts if you have any reason to be concerned about exposure to toxic gases.

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O2 POISONING SYMPTOMS - Oxygen Gas poisoning symptoms

Photograph of a Drager hand pump used to measure carbon dioxide levels in the environment.

Recommendations for tools and methods for detecting gases in buildings or outdoors

The photo shows a Drager colorimetric gas detection tube (also called a "color detector tube") used to test levels of a very wide range of specific gases in air. In an indoor air test (in our laboratory) this particular detector was not being used to measure oxygen, but rather carbon dioxide.

As the blue-stained portion of the tube shows, we found that the CO2 level was about 600ppm which is typical of indoor air and is an acceptable and safe level.

Colorimetric gas detection tubes such as those sold by Drager (or Draeger), Gastec, (two that we use predominantly) and by Kitagawa, and pumps from Drager, Gastec, Komyo Rikagaku Kitagawa, and RAE all work on a similar principle: a measured volume of gas (or air) is drawn through a tube which contains chemicals which change in color in response to the presence of a specific target gas (or range of gases) present in the sample.

By knowing the volume of gas or air sampled, the amount of color change read on a linear scale on the colorimetric gas detection tube can be translated into a very accurate measurement of level of gas present, described in percentage of the total air or in parts per million (PPM).

Other specialized gas detection methods include use of solid state circuity, CMS chips, and special instruments which may be designed to give a quick alarm or a reading in PPM for specific gases. Other gas and air monitoring equipment use pumps which collect and insert a specific volume of air into a vacuum container for later analysis. We've found that for typical field use, the colorimetric gas detector tube method is extremely convenient and very accurate, and it presents minimal requirements for instrument calibration.

What happens if a human breathes too much oxygen rather than too little?

Since we've discussed displacement of and reduction of the level of oxygen by an increase in CO2 or by dangerous carbon monoxide CO levels indoors in occupied buildings, (see links for these topics at the "More Reading" links at the bottom of this article ) let's take a look at the toxicity of oxygen itself and at what happens if the mix of gases in air changes in the opposite direction, increasing rather than decreasing the level of oxygen above normal amounts. Where does this occur? Two examples of exposure of humans to unusually high levels of oxygen occur in "oxygen bars" and in hyperbaric medicine.

Technical note on oxygen toxicity: What about too much oxygen in air: While high levels, even 100% oxygen are used for medical purposes in some cases (hyperbaric oxygen patients breathe 100% O2 at pressures above 2 to 2.4 ATM for 40-60 minutes),breathing high levels of oxygen can be toxic for humans and other animals. (Toxicity of excessive oxygen will depend on the oxygen level, the duration of exposure (breathing it), and individual characteristics).

But breathing high O2 air too long can produce toxic free radicals, producing effects that can be observed clinically in the human lungs or central nervous system. The current recommended limits of oxygen exposure are up to 24 hours with 100% O2, and up to 48 hours with 60% O2. OSHA does not have a permissible exposure limit (PEL) for oxygen.

What are the symptoms of exposure to elevated levels of oxygen?

The symptoms of excessive oxygen exposure include the following: (some or all of these might occur)

  • Dizziness can occur on exposure to high oxygen levels
  • Coughing and irritations of the throat can occur on exposure to high oxygen levels
  • Difficulties with vision or visual anomalies can occur at very high O2concentrations

What are the medical effects or symptoms of prolonged exposure to 100% oxygen?

If a person (say a medical patient undergoing hyperbaric treatment at high levels of oxygen and at increased pressure) is breathes 100% oxygen for more than a day (24 hours) s/he may show the symptoms we listed just above, and also the following:

  • General physical weakness or a sense of exhaustion or fatigue can occur at very high O2concentrations
  • The patient may experience pain joint and muscle pain
  • The high oxygen prolonged exposure individual may experience numbness and tingling in arms and legs (like when your leg "falls asleep")
  • Heart palpitations may occur
  • The individual may complain of a headache
  • Some patients complain of nasal congestion or (perhaps similarly-caused ear clogging, congestion, and pain, perhaps caused by swelling of the mucous membranes
  • On 24 hour exposure to 100% oxygen additional medical symptoms include the development of fever, nausea and vomiting, and a (corresponding) loss of appetite
  • Experts also cite the obvious hazard of freezing-burns if someone comes in contact with liquid oxygen.

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