Enviro-Gard B combines microprocessor and volumetric airflow sensor technology to control and maintain precise airflow. Even as the HEPA filter becomes loaded, fan speed is automatically adjusted to compensate. Consistent airflow is provided for each ventilated Micro-Isolator rack, regardless of the number of cages being housed. Each unit is equipped with an LED digital display of airflow. HEPA filter, pre-filter and fan status is indicted by green and red indicator lights.