Laminar Flow Hoods help in maintaining a controlled environment on a workspace for tests that require zero particulate contamination. Laminar means a flow or being along constant streamlines, without any turbulence. These hoods remove contaminants through a continuous airflow across the work surface. Laminar flow hoods generate air streams that move at the same speed and in the same direction. As such, there is an elimination of airflow swirls which can affect the purity of the workbench.
There are 2kinds of Laminar Flow Hoods –Horizontal and Vertical laminar flow hoods
· In this device, the air is drawn in and cycled through a pre-filter that removes coarse particulates. Then the air goes through a HEPA filter and then it is blown across the work surface horizontally.
· The filter or the fan unit is attached to the back wall of the hood. Air is pulled from the backside of the unit.
· The air flows from the back portion to the front, towards the operator or user.
· There are air slots on the side that minimize any turbulence in the work area.
· The product to be worked on must be placed at least 15 cm away from the front and sides of the Laminar flow hood. It also must be 5 cm away from the back, where the filter is installed.
· As the flow is from behind, incorrect product placement can obstruct airflow.
· These are most suitable for compounding sterile products.
· No hazardous / chemotherapy compounds must be handled in this type of hood.
· The workspace turbulence is lesser, and the workspace depth is larger.
· Contaminants can blow onto the face of the operator.
Vertical Laminar Flow Hood
· In this device the air is drawn and cycled through a pre-filter as well, to remove coarser particles. After going through the HEPA filter it is blown vertically on the work surface. Some air is recycled, and some part is exhausted externally.
· The filter or fan unit is installed on the top of the hood (the ceiling). Air is taken from the top of the unit.
· The plenum at the back allows recirculation of air while reducing the percentage of contaminated air going through the filter. This extends the filter’s life.
· The air blows in from the top, while the intake is at the bottom. Some part of the filtered air is exhausted through the bottom opening and some is recycled.
· The air flow from the top must not be obstructed through incorrect product placement.
· These devices are a little more expensive than a horizontal device because of the external ventilation.
· These devices can be used for chemotherapy compounds as well.
· The chances of contaminants blowing into the face of the operator are lesser.
Both the devices serve similar purposes – to provide a pure environment for the handling of products that will be destroyed if they come in contact with contaminated air. Each of themneeds to be chosen based on the purpose of the work.