Anesthetic agent analyzers fail when drug from a HFA propelled pMDI is administered. Most anesthetic vapor analyzers use infrared absorption at 3.3 micron. At this wavelength, substance like methane has been reported to interfere with the accuracy of measurement of anesthetic vapor. The anesthetic gas monitor 1304 (Brüel and Kjaer) which functions at 10.3-13 micron wavelength was not affected by methane. Is it possible, HFA with its structural similarity to inhaled anesthetic agents may be responsible for faulty reading of anesthetic vapor concentration in two of our monitors? Further evidence is needed to support this finding. Anesthesiologists need to be ever vigilant and recognize the need for smarter designs of anesthetic agent analyzers with changing array of drugs administered during anesthetic management.