Indoor radon concentrations were determined with the use of simple electronic systems were commonly used as detectors for different environmental pollutions. In this concern, a potentially very simple life-saving detector-a radon detector was investigated. Where, it is well known that radon gas is one of the most dangerous gases, as well, it leaks easily for the ground. Radon concentrations have been measured, successfully, in different locations at the Nuclear Materials Authority site at Qattamya, Cairo, applying a prototype, simple ion-chamber monitor, and well established radon monitor (RTM 1688-2-Radon Monitor). The radon concentrations were found to be in the range of around 16.7 - 20.7 Bq./m3, although it shown to be with less levels (around 10.3 Bq./m3) at ventilated basement hall. The obtained data from both systems were found to be in an excellent agreement.