Retest on radon

I did a radon test for a buyer and the level came back high, 13 pCi/l. The seller is installing a mitigation system and the buyer wants me to retest after the system is put in. I am wondering where to put the test canisters. The canisters were side by side for the first test, in the basement. Should I now put the canisters on different levels ( basement, first floor)? Any thoughts?

Same exact protocol as before… Lowest level, no more than 4 inches apart.

Only truth be known, the proper protocol for the installation company is to do a post mitigation test anyway. So your second test would be redundant.

And in situations like this, redundancy is a good thing. Personally, I believe that clearance testing should never be performed by the company performing the repairs.

And I agree, exact same protocol as the first test.

The buyers want an independent test done after the installation. Thanks for the help.