Salut @akosior,
The density of dry air is 1.29 grams per liter (0.07967 pounds per cubic foot) at 32° Fahrenheit (0° Celsius) at average sea level barometric pressure (29.92 inchs of mercury or 760 millimeters).
• At sea level and at 15°C , the density of air is 1.275 kg/m3. This is the value of the ISA or International Standard Atmosphere.
• At 20 °C and 101.325 kPa, the density of dry air is 1.2041 kg/m3 → STP (standard condition for temperature and pressure) [1]
Also the National Institute of Standards and Technology (NIST) uses the temperature of 20 °C (293.15 K, 68 °F) of an absolute pressure of 1atm at a density of 1.2041 kg/m3
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