To use an FGA the operator should know what the readings mean , anyone using an FGA has to be familiair with,
CO2max
Calculating excess air from 02 measured.
Calculating CO ppm against CO2% (ratio)
This is the difference between looking @ the figures against knowing what they actually mean.
Thank you for your response but that's not really the answer I need.
Is it against the law to use one if your not gas safe registered?