I don't believe so, according to the law of physics (as I understand it) .
Air and water vapor under typical situations, including inside a pressure cooker, are always mixed in exact constant proportions based on temperature and pressure. The air coming out of the pressure cooker is not just air, and the remaining water vapor inside the pressure cooker is not just water vapor. When they say air humidity is 100%, all that means is that the water vapor in the air at that pressure and temperature has reached it max saturation proportion relative to air. It does not mean that there is no air. As a matter of fact, the same amount of air molecules is still there.
Think salt water solution. there is a variable % of salt that can be dissolved in water , depending on temperature. When you reach 100% saturation, it does not mean there is no water in the solution. Interestingly you can add salt to water up to 100% saturation without increasing the volume of the mixture.
Also, water vapor is not visible. Steam is no longer vapor, it is water droplets you can see.
Even "pure" water has air in it. That also is a function of temperature and pressure.
dcarch
