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Name: Teressa R.
Status: Educator
Age: 40s
Location: N/A
Country: N/A
Date: April 2003


Question:
I checked the Archives and found that question #5 in the oxygen category asked Dr. Pam about human oxygen requirements but no specific answer was given. Considering the government recommendation that a "safe room" be prepared (though airtightness seems an unrealistic goal), shouldn't oxygen requirements per capita be known to determine the size of the room to be prepared in relation to the size of the family living in it? I have a large family and if this precaution is of any benefit, I want to choose and prepare knowledgeably. So, what ARE human oxygen requirements for elementary aged children to adults?



Replies:
Dear Teressa, A VERY reasonable question. The fact that the government has not provided this information is another indication that it should not be taken seriously. However,

I found a web site which stated that an average adult each day consumes 4 lb of food, 2 lb of water, and 6 lb of oxygen. I could not find a corroborating site, but the numbers seem roughly reasonable. Assuming 6 lb of oxygen per day is right, how large a room do you have to seal? Incidentally, an exercising adult uses oxygen at about 15 times this rate, so remain calm!

6 lb is about 2.73 kg. Since a mole of oxygen has a mass of 32 gm = 0.032 kg, an adult needs about 85 moles per day. Since a mole under standard conditions (atmospheric pressure, 300 C) occupies 22.4 liters, 85 moles occupies about 1900 liters or 1.9 m^3. But air is 21% oxygen, so about 9.1 m^3 of 321 ft^3of air is required for one adult for one day. If your ceiling is 8 ft high, this means you need 40 ft^2 of floor area per adult per day. So a room 20 ft square (400 ft^2) would provide for 5 (quiet) adults for two days. That air would be rather stale, so you would want a factor of at least 2 or 4 to make the air more breathable after two days.

I hope you find this discussion useful and I hope MUCH more that you will never have the need to use it!

Best, Dick Plano

Professor of Physics emeritus, Rutgers University


Second Note as follows:

I had looked around and had not found the FEMA recommendation of 10 ft^2 to provide an adult with oxygen for 5 hours. However, I find it in remarkably good agreement with my numbers.

Remember, I said 40 ft^2/adult/day which give 8.3 ft^2/adult/5 hours, in amazingly good agreement with the 10 ft^2 quoted by FEMA. With my safety factor of 4, that becomes 33 ft^2/adult/5 hours, which is much more conservative than FEMA's recommendation. Incidentally, I think they should point out that it's the volume of the room, not the area, that matters.

I don't believe the concentration of carbon dioxide matters (unlike carbon monoxide). After all soft drinks are filled with carbon dixoxide. If the nitrogen in the room were replaced by the carbon dioxide and the oxygen level remained constant, I don't believe there would be a problem.

However, I am certainly NOT an expert on medical matters and deeply appreciate enlightenment.

Many years ago I did a study on whether static sparks could cause fires in oxygen tents. I was at Columbia and Prof. Leon Lederman gave me the opportunity because he was afraid of getting in trouble. I was young and foolhardy and made a pioneering study which was published in American Hospitals magazine. For years thereafter I would occasionally get a letter from some legal authority describing an incident where a patient had been burned to death while in an oxygen tent, causing me to regret my foolhardiness. However, I believe my results were correct and, in fact, in each case I eventually got a letter stating that the patient had been smoking! Nonetheless I do not wish to be considered or even to become an authority on this matter.

Best, Dick Plano...



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