Talking your customers into letting you double check what they believe to be true can be tricky. Some times, customers can actually get in the way of you solving their radon issues.
It doesn't cost anything to double check non-living spaces such as attics and crawlspaces when searching for passive radon pipes. Many of them terminate in the attic or behind knee walls.
Watch this video to learn how I convinced a very knowledgable homeowner to let me double check his home. By doing so, HE saved a lot of money.