Portable gasoline generators are very useful during power outages caused by snow storms, hurricanes, tornadoes, and earthquakes. If not used outdoors and away from the home, the consequences can be deadly. Due to the fatality rate caused by the poisonous carbon monoxide (CO) gas emitted from portable gasoline generators, the need for CO reduction and automatic generator shutdown has increased. This thesis presents the Engine Management System (EMS) used to reduce CO emissions from a commercial off-the-shelf Coleman Powermate 7000 Watt generator. Although reduced emissions was accomplished, there was still a need for an automatic shutdown feature in the event the generator was operated in an enclosed environment. Having operated in this type of environment, the generator's poisonous exhaust depletes the environment's oxygen (O2) content causing the intake air temperature (IAT), fuel pulse width (FPW), and fuel pulse width correction of the engine to change. The O2 depletion shutdown algorithm uses these variables as inputs in order to calculate a pseudo-derivative based upon a moving average for each input. A comparison is performed on each pseudo-derivative and if all three have met unacceptable limits for a predetermined period of samples, the engine will be shut down. The algorithm implemented in the engine control module (ECM) was tested under various loading conditions and proven to be successful under all loading conditions. This thesis presents the algorithm and test results from The University of Alabama and the National Institute of Standards and Technology.