Average urban and agricultural soil concentrations range from 4 ppm to 6 ppm.
Globe and Mail (2003)
In humans, three ppm would be considered potentially poisonous to brain tissue.
Times, Sunday Times (2015)
The highest playground reading the group found was 147 ppm.
Globe and Mail (2003)
As carbon levels continue to rise at a rate of around three ppm, such occurrences could become dangerously commonplace.
2019, 'Carbon Dioxide Levels Reach Highest Point in Human History', Smithsonianhttps://www.smithsonianmag.com/smart-news/carbon-dioxide-levels-reach-highest-point-human-history-180972181/
A typical emission might be laced with anywhere between 0.001 and 1 part per million (ppm) of hydrogen sulphide.
Times, Sunday Times (2012)
At the time, the site’s carbon levels hovered around 315 ppm, but by 2013, they hadsurpassed 400 ppm.
2019, 'Carbon Dioxide Levels Reach Highest Point in Human History', Smithsonianhttps://www.smithsonianmag.com/smart-news/carbon-dioxide-levels-reach-highest-point-human-history-180972181/
For those aged 3 to 6, use a pea-sized blob of 1,350 to 1,500 ppm fluoride paste, available from pharmacists.
Times, Sunday Times (2008)
It is now at 392 ppm.
Times, Sunday Times (2012)
The concentration of carbon dioxide in the atmosphere in 1992 was just over 350 parts per million (ppm).