Extraction Volume Calculator
Build a schedule of fume cupboards, assign them to fans, and instantly calculate the extraction volume required per fan. Use the energy saving section to estimate the impact of VAV and AutoSash on running costs.
Fume Cupboard Schedule
| Reference | Sash Width (mm) | Sash Height (mm) | Face Velocity (m/s) | Fan | ||
|---|---|---|---|---|---|---|
| | ||||||
| No fume cupboards added yet. Click "+ Add Fume Cupboard" to start. | ||||||
Energy Saving Features
Fume cupboard extract systems are one of the largest energy consumers in a laboratory. Variable Air Volume (VAV) and AutoSash technology can dramatically cut running costs without compromising safety.
Variable Air Volume (VAV)
A Constant Air Volume (CAV) system runs its fan at full speed continuously, extracting the same volume regardless of sash position or occupancy. In a VAV system the fan also runs at a fixed speed, but a motorised damper on each fume cupboard modulates in a closed loop with an airflow sensor to maintain a fixed face velocity as the sash moves. A separate bleed air damper is controlled to maintain duct static pressure and efflux velocity at the discharge point as individual cupboard dampers close down. A minimum volume setpoint of 20% of design volume ensures safe containment is maintained at all times.
Energy Savings Estimator
CAV (annual energy)
100%
VAV (annual energy)
Estimated Annual Energy Saving
Airflow Profile - Typical Working Day
Annual Energy Consumption — CAV vs VAV
AutoSash
Studies show laboratory fume cupboard sashes are left open between 60-80% of the time when not in active use. AutoSash detects when the user steps away and automatically closes the sash to a safe minimum height, instantly reducing airflow and fan power.
Because air volume is directly proportional to sash opening height, a sash closed to 100mm extracts just 20% of the volume of a fully open 500mm sash. Fan power at 20% flow (cube law) is just 0.8% of full speed, a near-complete elimination of extract energy during unoccupied periods.
Air Volume vs Sash Height
Savings Estimator
Annual Energy — Standard vs AutoSash
Standard (annual)
100%
Energy saving
Variable Speed Drive (VSD)
In a CAV system, a manual damper is commonly used to balance the fan against the installed ductwork resistance. The problem is the fan motor continues to run at full speed, and the damper simply dissipates the excess energy as heat and noise rather than reducing consumption.
Fitting a Variable Speed Drive (inverter) allows the supply frequency to the motor to be reduced, directly slowing the fan to match the system resistance. Because motor input power follows the cube of the speed ratio, even a modest reduction from 50 Hz to 40 Hz cuts input power to just 51% of full speed, with no throttle losses and no excess heat.
This makes VSDs particularly valuable in CAV installations where the design flow has been achieved at below-maximum fan speed. Rather than wasting that headroom through a damper, the VSD permanently reduces input power to exactly what the system requires.
3-Phase Fan - Frequency vs Power
Fan speed
of full speed
Input power
Annual energy
8,760 hrs/yr
Annual saving vs 50 Hz