The Operating Mode option on the Fume Hood Setup menu opens the Set Operating Mode popup
screen. You can
configure the HMS1655 for one of three operating modes:
- Occupied: The Occupied mode configures the HMS1655 to maintain the fume hood sash opening face velocity at a safe level for the operator. While OSHA does not use specific requirements for fume hood face velocity, the most widely accepted references on the subject of fume hood face velocity include the ANSI/AIHA Z9.5 American National Standard for Laboratory Ventilation and the National Research Council’s Prudent Practices in the Laboratory, which both recommend face velocities of 80 to 120 ft/min.
- Unoccupied: When the fume hood is not in use, you can set the operating mode to Unoccupied, which reduces the maintained face velocity to minimize the amount of energy consumed in this mode. These face velocities fall in the range of 40 fpm to 60 fpm. The HMS1655 fume hood controller continues to monitor the face velocity in both operating modes, and triggers alarms whenever the measured face velocity deviates far enough from the target setpoint.
- Decommissioned: To further reduce fume hood energy consumption when it is not in operation, you can set the operating mode to Decommissioned, which reduces the maintained face velocity to near zero. This operating mode also minimizes the noise associated with the exhaust when you select lecture mode. While in the Decommissioned operating mode, the HMS1655 disables all audible and visual alarms associated with the face velocity of the fume hood. The sash is continually monitored in the Decommissioned operating mode and can sound the audible alarm if left in the high position for an extended period of time. To quickly switch to Occupied mode, tap Occupied on the main display at any time while in Decommissioned mode.
Note:
While the HMS1655 is in the Occupied or Unoccupied operating mode, the main display screen
includes an emergency button that enables the fume hood controller to immediately
move the exhaust damper to the fully open position and maximize the face velocity at
the sash opening. The Press for Emergency Purge button appears at the bottom of the
main display screen and does not require you to enter a password to activate Maximum
Flow mode. See Figure 1 for more
information.
- If you trigger the Emergency purge mode, tap Cancel Emergency Purge on the main display screen to cancel it.
Figure 1. HMS1655 emergency purge
