Laboratory Laminar Airflow
There are two different kinds of laminar flow hoods: vertical and horizontal. In a vertical laminar flow hood, the filter is above the workspace and the unit directs air downward. And, in the horizontal laminar flow hood, the filter is behind the workspace and the air moves forward.
Vertical Flow Hoods
Often, labs choose vertical flow hoods because they look like much smaller versions of cleanrooms. Cleanrooms also have fans and filters installed in the ceiling to direct airflow. This means that overhead clearance should be verified before selecting one for your lab.
Vertical flow hoods reinforce the gravitational pull and sweep particles outside of the unit. Usually, they exit the hood through an access area in the front of the flow hood. Generally, most consider them more effective in protecting the lab personnel who operate it.
Horizontal Flow Hoods
Horizontal flow hoods require some additional depth in the lab in order to accommodate the fan and filter unit. With horizontal flow hoods, the fan and filter are on the back of the unit. Therefore, if there’s a limit to your space, a horizontal flow hood might not be the best choice for you.
Like vertical laminar flow hoods, the airflow does initially come from the top of the unit. However, it’s very quickly shifted downward and is processed across the workspace in a horizontal direction. The constant, filtered airflow is ideal for the preservation of samples and materials handled within the flow hood. If you plan on handling anything hazardous, a horizontal laminar flow hood is definitely not the ideal choice.
Neither a vertical nor a horizontal flow hood should be used to handle biohazards. Only approved containment systems like biosafety cabinets should be employed during processes requiring Biosafety Level 2 or 3 containment.
Both models should run for (at least) fifteen minutes before you begin working within them. Running the fan will clear any airborne particles before you use it.
Required some of the laminar testing.
- Air velocity tests for contamination protection
- HEPA filter checks for leakage or contamination
- Surface testing for bacteria or fungi
- Light and sound measurement for worker comfort level
- Airflow visualization to verify the hood is providing non-turbulent airflow