Carbon dioxide makes the hydrogen combustion process unstable and destructive, thus affecting the efficiency and effectiveness of hydrogen energy use. Thus, it is very important to monitor CO2 in hydrogen gas. All-inorganic perovskites are used for optical sensing due to their excellent optical properties, and photoluminescence sensors made from them can monitor gas concentration. However, the toxicity and intrinsic instability of lead-based perovskites have limited their commercial development. Meanwhile, perovskites have rarely been studied in the mid-infrared range. Herein, Cs2AgIn1–xErxCl6-ZBLAN perovskite fluoride glasses with outstanding mid-infrared luminescence are successfully prepared. A CO2 monitor device is fabricated using a Cs2AgIn1–xErxCl6-ZBLAN perovskite fluoride glass. The dense and inert nature of the glass is used to isolate the lead-free perovskite Cs2AgInCl6 from the external environment, thereby improving stability. The luminescence intensity of the Cs2AgIn1–xErxCl6-ZBLAN perovskite fluoride glass can still be maintained at more than 90% of its original level after 35 h of continuous UV lamp irradiation at 365 nm. The substitution of Er3+ for In3+ to form Cs2AgIn1–xErxCl6-ZBLAN perovskite fluoride glasses makes them promising candidates for future mid-infrared-emitting materials.