Yes Scott, the 60 hours is the MINIMUM that you can leave the monitor when closed-house conditions were not maintained for 12 hours prior to your arrival. The you would ignore the first 12 hours of your CRM data when calculating the final test result. Extra data (i.e., leaving the monitor for another day or two) provides more information about the house conditions and radon patterns so I encourage longer test lengths when time permits.
Regarding Mr Valley’s opinion on passive tests when the 12 hour period was not maintained, they are not consistent with the EPA Protocols. IN essence, when one arrives at a house with open windows and doors there are two options. 1) Close the windows for at least 12 hours and then make a return trip to start the test, which means extra gas and a third trip. Or, 2) Close the windows and doors, start the test, but the test MINIMUM is now 96 hours, or 4 full days.
This is a common mistake because EPA’s guidance in the protocols is more vague in the abbreviated versions of their documents such as the Home Buyer’s and Seller’s Guide to Radon and A Citizen’s Guide to Radon. Those documents were developed from two larger protocol documents, which I reference for you below:
Protocols for Indoor Radon and Radon Decay Product Measurement in Homes (EPA 402-R-92-003)](http://www.epa.gov/radon/pdfs/homes_protocols.pdf)
2.3.2 Closed – Building Conditions
“…In addition to maintaining closed-building conditions during the measurement, closed-building conditions for 12 hours prior to the initiation of the measurement are a required condition for measurements lasting less than four days…”
“In test lasting less than four days (96 hours), closed-house conditions should be maintained for at least 12 hours before conditions should be maintained while the test is in progress;…”
3.4 Measurement Checklist
• When doing short-term testing lasting less than four days, it is important to maintain closed building conditions for at least 12 hours before the beginning of the test and for the entire test period. Do not operate fans or other machines that bring in air from the outside.
Indoor Radon and Radon Decay Product Measurement Device Protocols (EPA 402-R-92-004)](http://www.epa.gov/radon/pubs/devprot2.html#1.2)
**1.2.2 Measurement Conditions
**In addition to maintaining closed-building conditions during the measurement, closed-building conditions for 12 hours prior to the initiation of the measurement are a required condition for measurements lasting less than four days, and are recommended prior to measurements of up to a week in duration.
I hope this is helpful.