How far can your dog scent you?

While there are variables, such as wind direction, strength and sustained flow, there is solid, established, evidence that some creatures, notably carrion feeders such as vultures, are able to detect very small particles of a scent (decaying flesh as an example), down into a very few parts per million. Vultures are not primarily sight feeders, but can detect and react to a scent, under favorable conditions from miles away.