Orion Fans AFM modules can operate an optical LED, audible alarm, or send a signal to a control device when airflow falls below 8.2 feet per second, due to fan filter clogs, foreign materials coming into contact with the fan blade, or fan failure. The air flow monitor measures positive airflow when it is mounted to the front of the fan and negative airflow when mounted to the intake side. The IP20 rating and NEMA 1 certification assures the AFM modules are protected against dust and indirect splashing.