Monitoring indoor environmental conditions is provided. Sensor data and its corresponding time stamps from is collect from a number of environmental sensors within an enclosed environment. A set of all possible states is defined for a specified time period, each state representing a range of sensor data values. A probability of the system changing from any one state to another is modeled according to a Markov chain. When a new sensor data value is received from a sensor it is compared to a last sensor data value of a previous state, and a probability of transition from the previous state to the current state is determined. If the probability of transition from the previous state to the current state is less than a predetermined threshold, an anomaly is detected, and a service request is generated.