This page lists questions not directly related to global climate change, but that have been received and answered at CDIAC.
Q. How long can a given number of people survive in a sealed room of given dimensions before they run out of oxygen? (For example: How about 50 people in a room measuring 50' x 24' x 8'.)
A. Equation for estimating residence time in an enclosure without
oxygen replacement neglecting the buildup of carbon dioxide:
T= {V(r) - 12n}{21 - L} / 100nC
Where:
T = estimated residence time in minutes
V(r) = volume of enclosure in cubic feet
L = lower acceptable limit of oxygen in percent(OSHA Std is 19.5%, 12%
minimum before loss of consciousness likely, 15 % to account for people
with medical conditions)
n = number of people in enclosure
C = oxygen requirement in cubic feet per minute (0.007 ft3min-1 for a
70 kg male at rest)
Example:
Ten people put in an enclosure, volume 353 ft3. How long for O2 to drop from 21%
to 19.5%?
Assume a person's volume is 12 ft3.
{353 - (12x10)}{21-19.5} / 100x10x0.007 = 50 minutes [DOV]
Q. Is it possible to detect a person from a distance of 500 feet by measuring the presence of carbon dioxide?
A. Three possible techniques come to mind. One would be a spectroscopic analysis of an air column between point A and point B, 500 feet away. Atmospheric measurements of CO2 are sometimes made spectroscopically but are more typically (and accurately) made using an infrared gas analyzer (either with in situ air samples or air samples collected by flask). The second technique would be through chemical absorption and reaction. For example, C14 measurements are made using trays with NaOH solutions. The NaOH absorbs CO2 from the atmosphere. HCl is used to regenerate the CO2, and following a purification process the CO2 is analyzed in a proportional counter to assess the C14 content. A third possibility would be to use a mass spectrometer to analyze an air sample (mwt 44 or 45 for 12CO2 and 13CO2). [TAB]
Q. How much carbon dioxide is exhaled with each breath?
A. According to the text "Biology" by Claude A. Villee (Third Edition, W.B. Saunders Co., Philadelphia and London, copyright 1957), a person at rest inhales and exhales about 500 ml with each breath. That air consists of 150 ml of recently inhaled air that is in the larger air passages (where no exchange of gases between the lungs and blood stream occurs) and 350 ml of air that has been in the alveoli of the lungs. Thus, 150 ml of the 500 ml may be considered atmospheric air (approximately 0.04% carbon dioxide by volume), and 350 ml of the 500 ml may be considered alveolar air (approximately 5.3% carbon dioxide by volume). The average carbon dioxide content of the 500 ml of exhaled air is thus:
[(150 ml)/(500 ml) x 0.04% CO2] + [(350 ml)/(500 ml) x 5.3% CO2] = 3.7% CO2 by volume, which is equivalent to 5.7% CO2 by weight.
22.4 L of air at standard temperature and pressure has a mass of about 28.5 g (the difference in the average molecular weight of atmospheric and alveolar air is trivial, despite the differences in percent nitrogen, oxygen, carbon dioxide, and water vapor), so 500 ml of air has a mass of about 0.636 g. The 5.7% of this mass that is carbon dioxide would therefore would weigh about 0.037 g (equivalent to about 0.010 g of carbon). [RMC]
Q. Is carbon dioxide in the human body dangerous? How much carbon dioxide is present in human blood?
A. Carbon dioxide, a waste product of respiration, is normally present in body tissues. Blood carries carbon dioxide from the body tissues to the lungs, where it is exhaled (and where the blood is reoxygenated from fresh, inhaled air). According to the text "Biology" by Claude A. Villee (copyrighted 1957 by W.B. Saunders Company, Philadelphia and London), each liter of blood transports about 50 milliliters of blood from body tissues to the alveoli of the lungs. To give you an idea of the relative amounts of carbon dioxide in various parts of the body, the partial pressure of carbon dioxide in body tissues is about 60 mm of mercury, about 47 mm in blood in veins, about 41 mm in blood in arteries, and about 35 mm in the alveoli. Acidosis occurs when the removal of carbon dioxide from the blood is restricted (as in pneumonia); tissue death can result. [RMC]
Q. Should one be concerned about indoor levels of carbon dioxide and, if so, what are the potential effects?
A. Levels of carbon dioxide (CO2), even in a poorly ventilated room, must reach very high levels for this colorless, odorless gas to reach dangerous levels. The maximum concentration recommended by the National Institute of Occupational Safety and Health (NIOSH) for an 8-hour occupation is 5000 parts per million (ppm). The Occupational Safety and Health Administration (OSHA) also uses 5000 ppm as their threshold for occupational safety. Levels of CO2 have been known to reach 3000 ppm in homes, schools, and offices. Many things influence indoor concentration levels including the number of people in a room (human respiration), their size and level of activity, efficiency of the air ventilation system, presence and abundance of plants, time of day, etc.
There have been cases documented where indoor CO2 levels below 5000 ppm have caused discomfort and headache. Cases have also een documented where a 30-minute exposure at 50,000 ppm produced signs of intoxication, and a few minutes of exposure at 70,000-100,000 ppm can cause loss of consciousness. The American Industrial Hygiene Association (AIHA) reported that 100,000 ppm is the atmospheric concentration immediately dangerous to life. [RMC]
Q. Why is carbon dioxide used in fire extinguishers? what properties do they have and how does it work?
A. For ordinary combustible fires (e.g., wood, cloth, paper) to begin and continue, three factors must be present: oxygen, fuel, and a source of heat. Carbon dioxide (CO2) is used as a fire extinguisher because it is non-reactive and displaces the oxygen near the fire, thus depriving the fire of one of the three essentials. Without oxygen, a fire will go out. There are different kinds of CO2 fire extinguishers. One produces CO2 by the reaction of baking soda and acid (you can do this in the kitchen with baking soda and vinegar). Another kind consists of pressurized CO2, which - when released by the trigger - releases CO2 gas; in that case, the CO2 - being suddenly depressurized - also gets VERY cold (you can get frostbite if you hold the wrong part of the nozzle) - so this kind also chills the fire, in addition to depriving the fire of the oxygen it needs to continue. [RMC]
Q. What is the annual amount of CO2 that a mature tree will absorb (e.g., deciduous red oak vs. evergreen blue spruce)?
A. A mature tree absorbs no NET CO2 over the course of a year. What it takes up in photosynthesis, it loses in respiration and decay. [GM]
Q. What are some health effects from CO2 and other air pollutants?
A. The National Environmental Respiration Center (NERC) is a national research center established in 1998 by the U.S. Environmental Protection Agency (EPA) to facilitate scientific research for understanding and managing air quality health risks.
The NERC Web site provides access to information on published research, research projects, and scientific and regulatory issues involving mixtures of pollutants from natural and manmade sources. [RMC]
Q. How much oxygen is exhaled with each breath?
A. Air that is exhaled contains less oxygen and more carbon dioxide than atmospheric air, because of the gas exchange within the lungs. A typical breath with a volume of 500 mL consists of 350 mL of alveolar air (from deep within the lungs, where the gas exchange occurs) and 150 mL of air from the larger air passages (where no gas exchange occurs, and where the composition is similar to that of atmospheric air). The alveolar air is about 13% oxygen (versus 21% in atmospheric air) and 5% carbon dioxide (versus 0.04% in atmospheric air). As a result, the weighted (by volume) average for the total exhaled air is about 15.5% oxygen.
(source: Claude A. Villee, Biology, W.B. Saunders Co., Philadelphia and London, copyright 1957.) [RMC]
Q. In human respiration (Glucose + Oxygen = Carbon Dioxide + Water + Energy) why is it necessary to take in water and why is it necessary to excrete it?
A. In general terms, most of the processes within the human body depend on aqueous solutions or suspensions, so the body needs to maintain its water level. The human excretory system, in particular, uses water as the medium for ridding the body of urea (a nitrogenous waste product from the metabolism of protein) and other wastes; urine, for example, is about 96 percent water. Sweating, another important bodily process requiring water, is used to regulate body temperature and excrete metabolic wastes. More water is lost from the lungs and digestive tract. So water must be taken in to replace that which is lost.
(source: Claude A. Villee, Biology, W.B. Saunders Co., Philadelphia and London, copyright 1957.) [RMC]
Not exactly sure what you're looking for, or where to find it?
Search CDIAC's data holdings and Web area.
CDIAC
Oak Ridge National Laboratory
P. O. Box 2008
Oak Ridge, TN 37831-6290 USA
(865) 574-0390 or (865) 574-3645
(865) 574-2232 (FAX)
(04/24/98)