In handling critical scientific procedures, avoiding contamination is imperative.Laminar air flow hoodsalso referred to as clean benches are specially designed equipment that is used to provide sterile environments safe from contamination. The flow hoods allow the handling of any material or any critical process outside contamination. It is continuously bathed with pure air that is passed through High-Efficiency Particulate Air Filters commonly referred to us HEPA filters.
They provide a high level of localized contamination control to products and processes. This is achieved by providing streams of positive pressure, filtered air moving towards one direction. The delivery of laminar flow air moving along parallel lines from the laminar flow hood minimizes turbulence within the working area of the laminar flow hood.
- This technology has broad applications in industries, medical institutions and major laboratories that require extremely clean environments to conduct their procedures.
- They are also used to prevent contamination in PCR applications.
- In hospitals, pharmacies, and other healthcare institutions, they are utilized in the preparation of sterile v solutions.
- They provide excellent protection of equipment and materials from particulate contamination.
- Widely applied where there is no generation of bio-hazardous materials and operator protection is not required.
The clean bench (hood)
The laminar flow clean bench is a working bench or a contamination free enclosure. It provides protection to the products being worked on from potential contaminants like dust, fungi, and bacteria. The clean bench technology utilizes the HEPA filters to generate clean, fresh and purified air for the user at the bench.
These are High-Efficiency Particulate Air filters. These filters are considered the heartbeat of the lamina flow hood. Their principal function is to remove particulate matter that is airborne such as microorganism and dust particles. They, however, do not remove gasses and vapors. Most of the HEPA filters are made of borosilicate fibers. They are as thin as pieces of paper. The mechanism of particle retention is achieved by sieving, interception, inertial impaction and diffusion. The retention ability is so high to retain particles of 0.3 micrometers in diameter. This translates to 99.99 percent efficiency.
Laminar air flow
Laminar flow with respect to fluid dynamics refers to the movement of fluid in parallel layers without disruption. Laminar flow can be categorized into two depending on the direction of HEPA filtered the air. In horizontal laminar flow, the HEPA filtered air flows from the back of the clean bench towards the front opening in a horizontal direction. In this type, the HEPA filters are arranged perpendicular to the working plane. In vertical laminar flow, the filtered air flows from the top of the clean bench towards the front opening. The HEPA filters are aligned parallel to the working plane.
How are they designed?
They are designed to provide either vertical or horizontal airflow configuration. The choice made depends on the work done and the space available in the facility. Most hospitals and pharmacies use the vertical design to maximize the working area for use with compounds equipment. In the vertical layout, the air moves from the top of the working area to the bottom, it then leaves the working area through holes in the base. In the horizontal design, the air moves from the back of the working area to the front. The effectiveness of a flow hood depends on various factors. They include:
- A well-designed cabinet and handling system.
- Proper ergonomic design to ease operation and comfort for the user.
- They are fabricated from materials which are easy to clean like stainless steel.
How do they function?
It consists of a filter pad, a fan, and the High-Efficiency Particulate Air filters. The fan sucks air from the filter pad where dust particles are retained. From here, the prefiltered air passes through the HEPA filters where contaminating agents are removed. The resultant air is sterile and safe for use. Before use, the blower should be turned on for 30 minutes, and the hood wiped with alcohol soaked cloth .after this duration, repeat cleaning the hood again with a cloth soaked in alcohol. For maximum efficiency of the laminar air flow hood, the HEPA filters have to be efficient, and the airspeed has to about 0.5 m/s>.