The VLs draws air from all sectors in use. if the smoke level reaches the adaptive scan threshold, the VLs quickly scans each pipe to identify which pipe is carrying smoke. if more than one pipe is transporting smoke, the sector with the highest smoke concentration is designated as the First alarm sector (Fas).

Once Fast Scan is completed and the FAS identified, the VLS continues to closely monitor all four sectors (pipes) to monitor fire growth and maintain full protection of the area.

There are four alarm levels (Alert, Action, Fire 1 and Fire 2) for each sector (pipe) and the sensitivity for each alarm level can be set to ensure the optimum alarm thresholds are applied for each sector.

The VLS display has a bar graph to indicate the overall smoke level, alarm threshold and fault indication. The bar graph displays the individual sector smoke levels during the scanning sequence. There is an extra LED to indicate that a First Alarm Sector (FAS) has been identified and an extra function to the Silence Button to allow for Manual Scan to be initiated.