Just a few tips I have discovered over the years.
Have extra batteries - I purchased batteries that would last for the duration of test. Regular 9V wont last more than 24 hours.
I also carry battery clips as I have had to repair due to loose connections. I purchased at radio shack.
Keep a 25 ft or longer extension cord as some homes have no nearby receptacle.
Keep 2 to 3 prong adapters as some houses only have 2 prong outlets and extension cord needs a ground.
I have 2 folding tables, a box crate and 2 tripod stands for placing my detector the proper height off floor.
Keep extra power supplies as I have had them go bad. I have 2 on order as my spares are bad.
Keep an extra monitor in vehicle when you inspect homes as some clients decide last minute to test.
Keep extra forms with radon detectors. (Agreements, door hangers)
I hope this helps as it saved me a few times this week.
I always try to have backups as equipment can go bad.
PS I always like to see dirty underwear with skid marks:roll: