HCHO sensor having incorrect values

Hello,

My new HCHO sensor gives values that are much higher then the ones in the wiki example:
Vol = 0,22 under normal condition
Vol = 3,00 when placed above bottle of alcohol
Thus resulting in an Rs/R0 which doesn’t make sense according to the sensitivity characteristic diagram.

What to do? Is it a sensor defect? Or should I calibrate both Vol values in code?

Thanks!
Vera