61
The Environment / Re: What is the meaning of 400 ppm (0.04%) atmospheric CO2?
« on: 23/05/2013 22:36:47 »Quote
Where are these urban dwellers who get 1% CO2?Indoors, mostly.
From wikipedia article on indoor air quality
Quote
Carbon dioxide
Carbon dioxide (CO2) is a surrogate for indoor pollutants emitted by humans and correlates with human metabolic activity. Carbon dioxide at levels that are unusually high indoors may cause occupants to grow drowsy, get headaches, or function at lower activity levels. Humans are the main indoor source of carbon dioxide. Indoor levels are an indicator of the adequacy of outdoor air ventilation relative to indoor occupant density and metabolic activity. To eliminate most Indoor Air Quality complaints, total indoor carbon dioxide should be reduced to a difference of less than 600 ppm above outdoor levels. NIOSH considers that indoor air concentrations of carbon dioxide that exceed 1,000 ppm are a marker suggesting inadequate ventilation. ASHRAE recommends that carbon dioxide levels not exceed 700 ppm above outdoor ambient levels.[17] The UK standards for schools say that carbon dioxide in all teaching and learning spaces, when measured at seated head height and averaged over the whole day should not exceed 1,500 ppm. The whole day refers to normal school hours (i.e. 9.00am to 3.30pm) and includes unoccupied periods such as lunch breaks. European standards limit carbon dioxide to 3500 ppm. OSHA limits carbon dioxide concentration in the workplace to 5,000 ppm for prolonged periods, and 35,000 ppm for 15 minutes.
Quote
LD50 is about lethality.Yes
Do you understand that things can cause toxicity at levels that don't kill half the population?
Quote
And, since nobody said that 400 ppm would kill (or harm) anyone, it's a red herring.umm ... Is it not a red herring that you dragged in?
Quote
And I still maintain that a book that most people can't read isn't the best thing to cite.Agreed. It is a comfortable reference for henry though, because it dates from a time when we had a much poorer understanding of climate science, and the issue of global warming had not been recognized.
Quote
(BTW, how old are the data)As far as most of the content of the reference is concerned, 40 years plus. As far as LD50 is concerned, anything up to 100 years. But that is not really important because an old measurement of LD50 is likely to be just as reliable as a recent measurement.