The length , breadth and height of a room are 5 m, 4.5 m and 3 m, respectively.

Length of the room $=5 \mathrm{~m}$

Breadth $=4.5 \mathrm{~m}$

Height $=3 \mathrm{~m}$

Now, volume $=$ length $\times$ breadth $\times$ height

$=5 \times 4.5 \times 3$

$=67.5 \mathrm{~m}^{3}$

$\therefore$ The volume of air in the room is $67.5 \mathrm{~m}^{3}$.