Method how necessary is a co meter when doing CO method in small bathroom?

[eggsausagerice]

contemplating the CO method and i would like to be pointed towards affordable co meters on amazon or know if anyone is planning on going without one because they have a low budget like me. i've only done surface level research on the method but i plan on doing some more later as a fallback if the sn ends up not coming in. what co meters have people bought while preparing for the method? sorry for the low effort post, i'm about to go to bed.

 

[locked*n*loaded]

A CO analyzer would certainly add a level of confidence to the method. Just under $300 US is what I spent on one, including shipping and tax. Measures up to 10,000 PPM.