# What volume of 70,000ppm of CO2 does this represent in a room of 50dm^3 of air?

May 29, 2018

It represents ${\text{3.5 dm"^3 color(white)(l)"CO}}_{2}$.
A ppm is 1 "part" of something in ${10}^{6}$ of those things.
For example, 70 000 ppm of ${\text{CO}}_{2}$ means that there are ${\text{70 000 dm"^3color(white)(l) "CO}}_{2}$ in ${10}^{6} \textcolor{w h i t e}{l} {\text{dm}}^{3}$ of air.
50 color(red)(cancel(color(black)("dm"^3color(white)(l) "air"))) × ("70 000 dm"^3color(white)(l) "CO"_2)/(10^6 color(red)(cancel(color(black)("dm"^3color(white)(l)"air")))) = 3.5color(white)(l) "dm"^3color(white)(l)"CO"_2