- Laboratory Monitoring System
- Usage Profile
The following is the actual data in the chemical laboratory collected by Critical Environment Management System (CEMS).
Facility Overview
| Total Number of Fume Hoods: | VAV Fume Hoods x 48 VAV Walk-in Hoods x 2 CAV Snorkel Hoods x 48 |
| General Exhaust System: | Exhaust Fan, 60,000m3/h |
| > Exhaust capacity: 53% of the rated airflow is applied in consideration of concurrent operation rates. (Maximum concurrent operation rate: 30%, unoccupied hoods are half open) |
| > Control of fume hood face velocity: Airflow control valves maintain a constant fase velocity (0.5m/s) |
| > Room pressurization: Constant room pressure is maintained by keeping a certain offset between exhaust and air supply volumes. |
| > Usage based controls:By the signals from zone presence sensors the hood face velocities are automatically reduced to 0.3m/s when no one is present. |
Comparison between Conventional System and Critical Environment System
The data verifies that both safety and cost-reduction were achieved by optimizing the facility size and energy consumption.
[1] Reduction in facility cost by Critical Environment system
[2] Reduction in energy cost by Critical Environment system
Load Factors by Time Zones
This graph shows the load factors by time zones in percentages of actual exhaust volumes to the design exhaust capacity (=60,000m3/h) that were calibrated based on actual exhaust statistics.
In the case of this facility the load factor does not exceed 70% even at peak times. It means that the system has an adequate margin, allowing more fume hoods to be added.
Meanwhile, the fume hoods are operated round the clock. This suggests that a safe operation environment should be ensured 24 hours a day for chemical laboratories.
Concurrent Operation of Fume Hoods
This graph shows the actual time of concurrent operation of fume hoods and walk-in hoods in the laboratory during a month by numbers of hoods.
It suggests that of the 50 hoods 1 to 5 are constantly used at the same time and that the number of hoods in concurrent operation is not more than 13.
By taking the rate of concurrent operations in consideration for a laboratory design, downsizing of air supply and exhaust facilities is enabled.
