The phrase "quiet air" is correct and usable in written English.
You can use it to create a peaceful atmosphere or describe a gentle, still environment. For example, "The sun was setting, and a quiet air descended over the lake."
There were times when the owner had a quiet air.
He was 27 years old, tall, thin and had a quiet air of competence.
The morning that opened with the quiet air of a religious holiday was broken suddenly by the sound of a bomb.
After several days of relative quiet, air force jets were raging through the skies over Aleppo from just after midnight on Monday.
Dressed in black jeans and a black sweater, Ms. Maxwell has a quiet air about her, but she is far from shy.
That first morning, within 20 minutes of paddling away from Santa Galdana, Ben brought me into a bay where the sea was translucent and idle, and the quiet air was rich with the smells of myrtle, thyme, wild olive and Phoenician juniper.
But such time does exist, he added, "in my quiet air-conditioned seat on Metro-North".
The nine rooms, though plain and frugal-looking, are quiet, air-conditioned and have balconies overlooking the harbor.
It now provides the panoply of comforts that the well-heeled modern traveller demands: quiet air-conditioning, international telephones, satellite television, cappuccino and rather good cheesecake.
Ned Gaudette, 43, who travels to Midtown each morning for work, said he preferred a quiet, air-conditioned car to "running around like a mad man trying to shave a minute off my commute".
The experiment was performed in a quiet air-conditioned room with a constant temperature of 24 25°C.
