When I got my first condenser mic I could hear the traffic outside and I live on a quiet cul de sac type street. Drove me nuts trying to figure out what all those weird noises were in the background, like you said fans, air conditioner, dogs barking a block away.
What I do now is turn it down so it's not so sensitive that way I can get a little closer to it and it doesn't pick up the background, as much.
Still a big difference to a handheld dynamic.
But that sound....