Fascinating, and tragic. I still have (somewhere) the 1986 front page headline story (Houston Chronicle?) of this event. My recollection is that the explanation given in the immediate aftermath of the event was somewhat different, i.e., some unknown “toxic gas.†I had never heard this follow-up explanation.
However, there is quite a bit of confusion in one paragraph that I would like to untangle.
The paragraph begins, “CO2 is odorless, colorless, and non-toxic; your body produces it and you exhale some every time you breathe. Even the air you inhale consists of about 0.05% CO2.†Well, regarding the latter, yes; but that doesn’t mean that that CO2 isn’t toxic. For example, the NASA Spacecraft Maximum Allowable Concentration (SMAC) for CO2 is 10.0 mm Hg (1.3% at sea level pressure) for a one-hour period. The NASA Bioastronautics Data Book indicates that after only 80 minutes, at a ppCO2 level of ~18 mm Hg (2.4%), the subject can experience “mental depression, headache, dizziness, nausea.†At ~45 mm Hg (5.9%), the subject experiences “marked deterioration leading to dizziness and stupor, with inability to take steps for self preservation. The final state is unconsciousness.†Not exactly “non-toxic.â€
This toxicity has nothing to do with oxygen displacement (starvation) by an “inert†gas, e.g., nitrogen and argon, which typically comprise 78% and 1% of the atmosphere, respectively.
The paragraph continues, “What makes it a killer in certain circumstances is the fact that it’s heavier than air: If enough escapes into the environment at once, it displaces the air on the ground, making breathing impossible. A mixture of as little as 10% CO2 in the air can be fatal …†Again, at this concentration, the danger of CO2 is due to its toxicity, not the oxygen it displaces. As aforementioned, ~6% is enough to cause death by toxicity. By contrast, merely adding 10% CO2 to the existing environment will only have the effect of diminishing oxygen concentration by 9%, which is the equivalent of traveling from sea level to 2500 feet (770 m) elevation – hardly lethal.
The accounts of the witnesses also attest to these phenomena. Victims are said to have “quickly collapsed and died right on their own doorsteps,†which is altogether inconsistent with oxygen deprivation. Hypoxia symptoms, even in the presence of no oxygen, occur slowly (a few minutes), beginning with various subtle symptoms, then blackout, then unconsciousness. The description of the victims’ sudden unconsciousness would have to be due to very high levels of CO2.
Having said all of that, from the description of the event offered, it seems very likely that the balance of victims were exposed to near-100% concentrations of CO2, causing their instant unconsciousness, with death resulting from some combination of severe CO2 poisoning and oxygen starvation.
Brian Dunaway The Boeing Company Space Exploration Environmental Control and Life Support Houston, Texas
However, there is quite a bit of confusion in one paragraph that I would like to untangle.
The paragraph begins, “CO2 is odorless, colorless, and non-toxic; your body produces it and you exhale some every time you breathe. Even the air you inhale consists of about 0.05% CO2.†Well, regarding the latter, yes; but that doesn’t mean that that CO2 isn’t toxic. For example, the NASA Spacecraft Maximum Allowable Concentration (SMAC) for CO2 is 10.0 mm Hg (1.3% at sea level pressure) for a one-hour period. The NASA Bioastronautics Data Book indicates that after only 80 minutes, at a ppCO2 level of ~18 mm Hg (2.4%), the subject can experience “mental depression, headache, dizziness, nausea.†At ~45 mm Hg (5.9%), the subject experiences “marked deterioration leading to dizziness and stupor, with inability to take steps for self preservation. The final state is unconsciousness.†Not exactly “non-toxic.â€
This toxicity has nothing to do with oxygen displacement (starvation) by an “inert†gas, e.g., nitrogen and argon, which typically comprise 78% and 1% of the atmosphere, respectively.
The paragraph continues, “What makes it a killer in certain circumstances is the fact that it’s heavier than air: If enough escapes into the environment at once, it displaces the air on the ground, making breathing impossible. A mixture of as little as 10% CO2 in the air can be fatal …†Again, at this concentration, the danger of CO2 is due to its toxicity, not the oxygen it displaces. As aforementioned, ~6% is enough to cause death by toxicity. By contrast, merely adding 10% CO2 to the existing environment will only have the effect of diminishing oxygen concentration by 9%, which is the equivalent of traveling from sea level to 2500 feet (770 m) elevation – hardly lethal.
The accounts of the witnesses also attest to these phenomena. Victims are said to have “quickly collapsed and died right on their own doorsteps,†which is altogether inconsistent with oxygen deprivation. Hypoxia symptoms, even in the presence of no oxygen, occur slowly (a few minutes), beginning with various subtle symptoms, then blackout, then unconsciousness. The description of the victims’ sudden unconsciousness would have to be due to very high levels of CO2.
Having said all of that, from the description of the event offered, it seems very likely that the balance of victims were exposed to near-100% concentrations of CO2, causing their instant unconsciousness, with death resulting from some combination of severe CO2 poisoning and oxygen starvation.
Brian Dunaway
The Boeing Company
Space Exploration
Environmental Control and Life Support
Houston, Texas