Nick,
Please consider contacting Cartus Relocation Co. regarding Inter Nachi’s radon certification course. I just had a bad experience with this company, they require NHEA certification for radon testing, even though Maryland does not require it. I use Radalink, and know all of the testing protocals. If Cartus and other relo companies were aware of your certification program, they may be willing to accept Inter Nachi radon certification.