Smell outside my house
Yea, it all depends on the way the wind is blowing. If you think this is the issue, a quick thing to try is to extend the vent pipes up from there current height, just try a foot and see if that helps. Real simple to do, just use short length of pipe and a coupler. Since it is a test for smell I wouldn't even glue them, let them friction fit for a week or so and see if that is the issue, else look around. Do you have a septic as Slick said? That too could be the issue, what about the next door neighbors? You gotta look at everything.