Lets look at 2 gases a poison – Hydrogen Sulphide H2S And a benificial to all life nutrient – CO2
H2S http://www.drthrasher.org/toxicology_of_hydrogen_sulfide.html 10 ppm Beginning of Eye Irritation 50-100 ppm Slight conjunctivitis and respiratory tract irritation after one hour 100 ppm Coughing, eye irritation, loss of sense of smell after 2-15 minutes. Altered respiration, pain the eyes, and drowsiness after 15-30 minutes followed by throat irritation after one hour. Several hours exposure results in gradual increase in severity of symptoms and death may occur within the next 48 hours. 200-300 ppm Marked conjunctivitis and respiratory tract irritation after one hour exposure. 500-700 ppm Loss of consciousness and possibly death in 30 minutes to one hour of exposure. 700-1000 ppm Rapid unconsciousness, cessation of respiration, and death 1000-2000 ppm Unconsciousness at once, with early cessation of respiration and death in a few minutes. Death may occur if individual is removed to fresh air at once.
The most dangerous aspect of hydrogen sulfide results from olfactory accomodation and/or olfactory paralysis. This means that the individual can accomodate to the odor and is not able to detect the presence of the chemical after a short period of time. Olfactory paralysis occurs in workers who are exposed to 150 ppm or greater. This occurs rapidly, leaving the worker defenseless. Unconsciousness and death has been recorded following prolonged exposure at 50 ppm.
http://www.ncbi.nlm.nih.gov/pubmed/10998771 There were 80 fatalities from hydrogen sulfide in 57 incidents, with 19 fatalities and 36 injuries among coworkers attempting to rescue fallen workers.
CO2 Carbon dioxide is an asphyxiant. It initially stimulates respiration and then causes respiratory depression. High concentrations result in narcosis. Symptoms in humans are as follows: EFFECT: CONCENTRATION: Breathing rate increases slightly. 1% (10,000ppm) Breathing rate increases to 50% above normal level. Prolonged exposure can cause headache, tiredness. 2% Breathing increases to twice normal rate and becomes labored. Weak narcotic effect. Impaired hearing, headache, increased blood pressure and pulse rate. 3% Breathing increases to approximately four times normal rate, symptoms of intoxication become evident, and slight choking may be felt. 4 – 5% Characteristic sharp odor noticeable. Very labored breathing, headache, visual impairment, and ringing in the ears. Judgment may be impaired, followed within minutes by loss of consciousness. 5 – 10% Unconsciousness occurs more rapidly above 10% level. Prolonged exposure to high concentrations may eventually result in death from asphyxiation. 10 – 100%
http://yarchive.net/med/co2_poisoning.html All true, but the subjective distress is almost entirely caused by the high CO2. Humans don’t have good hypoxia sensors, and people have walked into nitrogen filled rooms and died, before they even realized there was anything wrong. You can breathe into a closed circuit which takes out the CO2 until you pass out from hypoxia, without much discomfort at all. On the other hand, in a submarine or someplace where CO2 is building up but there’s plenty of oxygen, it’s intensely uncomfortable, and feels like dying. So does breathing that 5% CO2 95% O2 medical mix they treat CO victims with.
And when the CO2 hits about 7% to 10% of your ambient air, you DO die. Even if the rest is O2. It’s CO2 narcosis, and it shuts you down. 5% CO2 is about 40 Torr, your normal blood level. So if you breath that, you go up to 80 Torr, enough to black you out unless you hyperventilate. Double your minute volume and you can get down to 60 Torr, but you feel crumby. At 10% there’s no way to keep below about 90 Torr, and (unless you’re a chronic COPD patient who’s used to high CO2s and has a high bicarb and other compensatory mechanisms) you black out. Then quit hyperventilating. Then quit breathing entirely.
http://www.therhondda.co.uk/gases/carbon_dioxide.html included to show that the combined effects of carbon dioxide and a shortage of oxygen are much more intense than either of the two conditions alone,
So firstly it is not benign above 50,000ppm Secondly it is not poisonous but it kills:
deaths : Look up “choke damp” in mines look up lake nyos 2000 deaths / lake monoun 37 deaths
So please cut the stuff about how CO2 is the stuff of life