How is it that Co2 is such a deadly gas ?

Carbon dioxide that is free in the atmosphere is not a dangerous gas to humans even if the concentration increases somewhat. The human body inhales oxygen and exhales carbon dioxide and in a closed space if the concentration of oxygen is reduced or the concentration of carbon dioxide is increased the gases will not be properly exchanged in the lungs to support life. An increase in the concentration of carbon dioxide in the atmosphere is a concern because it may trap solar energy rather than allow it to radiate into outer space. If in fact this could lead to global warming (the greenhouse effect) there might be adverse consequences. The issue is still being hotly debated by many scientists.

Varius effects can happen from higher concentrations of CO2, under 3% the effect of the human population is minimal. Some people might experience shortness of breath for example.

Over 3% the real problems start as humans now have less oxygen per breath. Sports and exorcise will become more difficult. Many labor intensive jobs like constructions will become harder. Much of Earth's smaller lifeforms will die at this concentration.

At 5% some people will die. Mostly those who need an artificial lung or have trouble breathing now would simply not get enough O2 out of the air and die.

Also most pet sized animals will be dead.

at 7% healthy people will experience headaches, fainting, lethargy and be nearly unable to function. And any animal smaller than a human will be dead at this point.

at 8.5% all but the most physically superior humans will fall unconscious in a few minutes. Most people and animals will die.

At 10% all animal life will be extinct.

But long before we hit 10%, the heat in our atmosphere will extinguish most life on Earth.

But why be concerned if the CO2 levels now are only at .003%?

Because the amount of CO2 being put into the atmosphere more than doubled from 1950 to 2000 and doubled again from 2000-2012. The amount of CO2 being soaked up from vegetation has decreased by almost half.

So at the rate we are going, our CO2 levels will hit the 3% levels by the end of this century and the above scenarios will be everyone's problem. Someone has already been born today that will die of catastrophic failure of the planet.

What a bunch of incomplete answers, at least the first 5-6.

CO2 now is a panic because the increasing amount of CO2 in the atmosphere is increasing the average global temperatures which is causing climate change (more violent storms, droughts in food raising areas) and melting the ice so water level is rising and current patterns may change (making England colder if the Gulf stream shifts.)

CO2 in general is deadly because it is heavier than air and if it collects in an undisturbed place, it pushes out oxygen and animals and people quickly suffocate and die. This happens in Africa where CO2 is released from volcano vents and rests in small valleys. Normally, this doesn't happen because there are few sources of pure CO2 and normally it is mixed by the wind and temperature changes. If a person is trapped in a closed space, the using up of the O2 breathing is what kills them although technically the CO2 is part of it.

Why do you think we exhale it? Because we don't want it in our bodies. Plants can obtain nutrients from CO2, animals can't. It's waste. Living in a world full of CO2 would (on a much less disturbing level) be like living in a world full of feces. The amount we exhale is easily canceled out by photosynthesis but with more carbon-emitters and less plants to get rid of it, the world's balance is being destroyed and CO2 levels are rising.

I will try to answer this question most correctly: 1) I believe that you confuse CO2 with CO - Carbon Monoxide, which is really lethal gas. CO2 is inert, that means it does not react when you breathe it.

On the other hand, when you breathe certain concentration of CO, you will experience so called Carbon monoxide poisoning, because CO binds with red cells much better then O2-your body wont get the oxygen it needs.

2)CO2 is not dangerous for humans directly, but as scientists suggest, it contributes towards the global warming which is very popular phenomenon these days.

CO2 by itself is not toxic. But if we breathe it, that CO2 takes the place of oxygen and we suffocate.

But the problem that you are talking about with CO2 is not that its deadly. The problem is that its a greenhouse gas. That means that it lets sunlight through, which heats the land. But CO2 doesn't let infrared (heat) energy out. So the land gets warm during the day but has no way to cool off at night - so it just keeps getting warmer.

Surely you've heard about global warming - CO2 (and methane) are the main causes of it.

Human activities such as burning fossil fuels, cutting down forests, etc. contribute to increaing CO2 in the air.

CO2 is not dangerous until it exceeds a volume greater than 25% of the whole. At present, CO2 represents 3% of the atmosphere, and human caused CO2 is 0.003%.

So we would have to hit levels in excess of 21,000ppm for it to become dangerous. Based on isotopic data, the highest seen on this planet, during the Cambrian period, was ~7,000ppm (at present we are at 385ppm which is almost the lowest ever seen on the planet...plant death begins at 250ppm).

So I think that regulation of CO2 is being done for a political purpose and not for an environmental reason. But then again, you'll notice that the only solutions for global warming you ever see always require a massive growth in government control, and a massive loss of individual liberty.

The main reason to regulate CO2 emissions is mainly because it is a greenhouse gas.

The air we breathe carries around 78% N2 and around 21%O2; CO2 and other gases add up to less than 1%. It is very unlikely that the CO2 level will come up to a level that the air is un-breathable.

However, CO2, being a Greenhouse gas, traps an emits solar energy in to the atmosphere. This contributes to a whole range of problems starting from ice-cap melting, disruptions to marine life, climate changes etc. That's why CO2 has become an issue.

The usual take on this question is an increase of deforestation combined with greenhouse gases, which CO2 is a contributor and a fear factor for many people since we burn a "lot" of fuel. We're just going to have to deal with it over a long period of time.

Keep in mind, the planet we live on sort of has a mind of its own. Severe average temp swings have happened in the past that did not include humans, but life went on. For some of us, this Malthusian argument is getting old, beating some dead wings as it were. Does fuel consumption increase greenhouse gas? I think so, but only time will tell to what extent.

Btw, your exhalation of breath -- of trillions of peoples breaths -- pales in comparison to natural methane emission when talking about atmosphere affect.

First off, no there is no way possible for a govenment to tell you how much to exhale. Rising levels are bad because CO2 and others like it chemically are called greenhouse gases. This means that more and more heat is trapped as the levels increase. This could melt ice caps and cause the sea level to rise. also cooling and heating of air cause tornados and hurricanes and destroys habitats. CO2 is not dangerous to our bodies directly because our lungs just get rid of it. Even if there was so much of it that we couldn't get enough oxygne( not gonna happen) you would already be dead because of the reasons I discussed earlier.