One of the most common sources of emissions and greenhouse gases (GHG) in the oil and gas industry is fired-based equipment, which needs to be minimized and mitigated to improve sustainable manufacturing systems. Local regulations provide allowable limits for GHG, which must be complied with. This study proposes a health index (HI) based emissions-monitoring system. The proposed HI quantifies the condition of the equipment's environmental efficiency to take corrective actions and improvement decisions. Also, the HI can be used as a national benchmark for regulation and improvement measurement purposes. A case study was applied to test the approach of a new health index in one gas plant in Oman, taking a stationary combustion steam boiler. The results show a good presentation of indices for each condition of GHG and the overall Health index for the equipment, which supports corrective actions.