Under normal circumstances, the fume hood operates according to the selected, normal exhaust flow control strategy. Special modes may be implemented for special circumstances that arise in a laboratory. Configuration and activation of any special operating modes should be based on documented safety procedures for the laboratory.
Fume hood
Occupancy schedule source – Specifies whether the fume hood responds to its own occupancy schedule or to one for the room.
Emergency Flow – In many laboratories, work procedures for handling a spill or other problem in the hood is to close the sash and press the button to call for more air flow. Details for increasing the flow level are configurable, and should be set according to the safety procedures of the laboratory. The controller can indicate this state to the BAS so it can be announced to selected personnel.
Unoccupied – The application may be programmed to respond differently depending on the presence of workers. Parameters for triggering sash opening alarms may change. Sashes should be closed when workers are present. If the client’s safety policies support the practice, air flow levels or velocities may change with occupancy. As an energy conservation measure, this is inferior to closing the sash.
Fire – Special flow rates can be selected to be applied in case a fire erupts in the facility. The application supports this function.
Decommissioned – The client’s activity may eliminate the need for a particular fume hood for a long time. The application supports putting the hood completely out of service for laboratories that have the necessary administrative procedures.
Several mode variables interact within the control application to determine the operating mode, based on configuration data and dynamic inputs. Some of these features help conserve energy in a laboratory, but might also affect safety. Decisions about what to implement and how should always include input from someone responsible for safety in the laboratory.
Fume hood sash
Presence detector for sash alert – Defines if the presence detector has an effect on the sash alert. If the presence detector alert is inactive, then there is no effect.
If presence detector alert is active and the presence detector indicates presence, then sash area / position is compared to the occupied alert area or occupied alert position to determine if sash alert should be on or off. If presence detector indicates absent, sash area / position is compared to unoccupied alert area or unoccupied alert position to determine if sash alert should be on or off.
Occupied alert area – When the sash is open beyond this level and fume hood occupancy is Occupied or Override to Occupied, or, presence detection alert is active and presence is detected, then fume hood sash open alert will be triggered.
Occupied alert position – When the sash is open beyond this level and fume hood occupancy is Occupied or Override to Occupied, or, presence detection alert is active and presence is detected, then fume hood sash open alert will be triggered.
Unoccupied alert area – When the sash is open beyond this level and fume hood occupancy is Unoccupied or Pending Unoccupied, or, presence detection alert is active and current detection indicates absence, then fume hood sash open alert will be triggered.
Unoccupied alert position – When the sash is open beyond this level and fume hood occupancy is Unoccupied or Pending Unoccupied, or, presence detection alert is active and current detection indicates absence, then the fume hood sash open alert will be triggered.
Maximum opening alert area – Defines maximum safe operating sash height. When the sash is open beyond this level, fume hood sash maximum alert, is triggered (Instant buzzer and yellow LED on ODP). This is not dependent on fume hood occupancy state or presence detection.
Maximum opening alert position – Defines maximum safe operating sash height. When the sash is open beyond this level, fume hood sash maximum alert, is triggered (immediate indication on ODP). This is not dependent on fume hood occupancy state or presence detector.
Check low sash for low air volume flow – Defines whether the system checks sash position upon a schedule change from occupied to unoccupied. If set to Inactive, the fume hood occupancy is allowed to go to unoccupied regardless of sash position / face area. If set to Active, sash must be lower than the unoccupied alert area or unoccupied alert position before fume hood occupancy can change to unoccupied. If set to Active and the sash is open during a schedule change, fume hood occupancy goes to "Unoccupied pending".
Switch-on delay to low air volume flow – The amount of time that must elapse after fume hood occupancy changes to Unoccupied, before fume hood operating mode changes from Control to Low air flow. The ODP will indicate this impending change if there are no alarms present.
Enable schedule override from ODP – (QMX3.P88 only) For a fume hood that follows an assigned schedule, setting to 1: Yes will enable the fume hood operator to manually override the schedule at the ODP. When the hand button on the ODP is pressed by the hood operator, the fume hood will remain in occupied mode until the command is released at the next scheduled occupancy state.