[interrupt_]

> I circulate air in my house every day

Might be hard to do that in really cold weather. I live in a place that's very warm and the windows are always open, so I can't relate.

[r00fus]

Two box fans + windows (ie, apartment) or a whole house fan in a larger house can circulate air quickly in 15m.

I find useful to do that even in winter (maybe not in North Dakota winter).

[colanderman]

Energy recovery ventilators make this possible. There are even inexpensive window-mounted units.