The Portable Monitoring Unit (PMU) was originally developed and used for measuring ammonia (NH3) and carbon dioxide (C02) concentrations and emissions from poultiy facilities, Its use entailed a substantial degree of manual setup and data processing, making deployment of multiple PMUs in field measurements a logistic challenge. The original commercial electrochemical (EC) sensor for NH3 is obsolete and no longer available. Thus, an effort to upgrade the PMU design was undertaken. A substantial redesign of the PMU system is reported in this paper, and includes an upgraded data acquisition and control system (DACS), wireless data transfer capability, and a new commercial NH3 EC sensor. An evaluation of existing EC sensors was performed, a sample of potential sensors was evaluated, and the selected sensor was further tested to characterize its accuracy and limitations. The performance of the upgraded PMU during field measurement in a commercial laying hen house and subsequent laboratory reassessment was evaluated and is reported here. Results demonstrate the feasibility of new system, termed the 1PMU (Intelligent Portable Monitoring Unit).