Today , with the advent of technology and the use of digital systems in industry , almost all process variables are measured by sensors . With modernization of digital systems and sensors , the use of alarm systems to monitor the performance of processes in the industry was considered . Concerning the abundance of variables and the definition of alarms for each variable , the probability of weakness of the system of alarms is significant and hence the improvement of the efficiency of alarm systems is important . The task of the alarm system is alerting the occurrence of any fault in the process . In this situation , when the value of a variable exceeds the threshold defined for it , the alarms are triggered visually or audibly to the operator and should be taken to identify and correct the alarms . According to the standard , the operator must receive up to 6 alarms per hour , but due to environmental factors , incorrect design of alarm systems and sensor wear , the operator receives more alarms per hour . It is desirable to receive one and only one alarm for each fault , but there are usually many alarms for the same fault that are known as nuisance alarms . The presence of false and nuisance alarms makes the operation of the alarms system difficult . The most important criteria for assessing the performance of alarm systems are the false alarm rate , the missed alarm rate and the delay in detecting alarms . Methods that have a significant impact on improving the performance of alarms include multivariate monitoring , threshold level design , model-based monitoring and data processing . In data processing method s, the use of an efficient filter improves the quality of alarms. Commonly used filters include moving average and moving variance filters . In this thesis , the effect of these filters on the performance criteria of alarm systems are studied. Then , by using quantitative methods and Mont-Carlo simulation , the optimal parameters for a moving variance filter are calculated and designed based on a compromise between delays in detection and optimal performance of the system . }Key Words} : Alarm Systems , Alarms Assessment Criteria , linear Filters , Nonlinear Filters , Moving Average Filters , Moving Variance Filters