I live in a condo in FL. Alone. In the winter, I can turn off the a/c AND not turn on the heat most days leaving my windows and patio door opened.
I've noticed a slight tinge of brown on the lace curtains by my kitchen window, lately.
In the warm months...like 8 or 9 of em...I use the a/c and change the filter every month.
I smoke inside, in my car, and first thing in the a.m. I usually lunt in the parking lot outside, before sunrise, to facilitate other daily function.
Regularity is the key to happiness here.