Found what I think is a good site and wondered about these tests for my home.
"The only way to know for sure is to have the house tested with a blower door, a device designed to locate the holes in the house and measure their size. Find a contractor who also has a duct tester to measure how leaky the ducts are."
Is there a duct tester device for flex? How does a blower door test locate leaks in certain rooms?