What is considered a "dangerous" level of CO2 in the atmosphere?

Question

What is considered a "dangerous" level of CO2 in the atmosphere?

Answer 1

enough to kill you

Answer 2

It depends on what you mean by dangerous.  If this is a climate change question, the answer is a matter of much debate: by some reckoning, we have already passed it.  The current CO2 level in the atmosphere is 385ppm (by volume)

If you mean the level of CO2 that will cause a person to have breathing problems, this is higher, but the amount that can be tolerated depends upon exposure time.  Generally, people will get uncomfortable in a room containing 1000 to 2000ppm CO2.  The upper limit for short-term exposures is about 3 percent (30000ppm), but by slowly acclimating to higher levels, people can withstand 3 percent for about a month.