air quality sample came back inconclusive

I had a Z5 cartdrige sample come back inconclusive, should I retest?

Probably be a good idea, or use a different cartridge and send it to a different lab.

Try using EMSL Analytical Laboratories. My guess if you are using a Z5, you are also using Pro-Lab. I have had some bad experiencees with them in the past and will never use them again for mold samples.