An increase in the ambient pressure at a constant temperature results in the compression of air and, thus an increase in the air density. Conversely, the air density decreases with increase in the temperature while pressure is maintained constant.

Table 2.2. Dependency of air density on temperature

Temperature, T in °C	Temperature, T in K	Density of air, ρa (kg/m3)	Relative change in air density (%)
35	308.15	1.146	4.87
30	303.15	1.164	3.30
25	298.15	1.184	1.68
20	293.15	1.204	0.00
15	288.15	1.225	-1.74
10	283.15	1.247	-3.53
5	278.15	1.269	-5.39
0	273.15	1.292	-7.32
−5	268.15	1.316	-9.32
−10	263.15	1.341	-11.39
−15	258.15	1.367	-13.55
−20	253.15	1.394	-15.80

The sensitivity of the air density to temp and pressure is presented graphically in Fig. 2.5. It can be observed that the air density is highly sensitive to the other state variables.