CO2 Detecting Tubes

[Blue53]

This maybe stupid, but please help:

Can you reuse those disposable CO2 detection tubes over again?

I'm using a co2 tank w/Control Wizard regulator.

I have it set at .25 and the tube measured 500 ppm

I raised to .35 and it measured 1500 ppm (or is this truly 1000 ppm)

I have a closet I build that is totally enclosed except for intake and exhaust fan. Closet is 4' x 7' x 6' high.

Thanks, Blue