What is the principle and procedure of reverse laminar air flow?

Answer 1

Laminar air flow cabinets blow air through filters that eliminate potential sources of contamination, e.g. bacteria and yeasts. This air flows in a continuous stream over the work surface, preventing unfiltered air from entering the workspace. Because most cells are cultured on relatively rich growth medium it's essential to remove potential contaminant, so that only the cells you want will grow on the medium.

Answer 2

Reverse laminar air flow operates on the principle of providing containment of contaminated air by air movement. Prefilters capture airborne contaminants in the rear of the room or hood, and the velocity of the air entering the filters is accelerated to reduce the number of particles that recirculate into the room. The reverse flow draws contaminants away from the working area, protecting workers from recirculating aerosol contaminants.

Answer 3

Laminar air flow is usually used with biological safety cabinets (BSCs) that are designed to protect the operator, the laboratory environment and work materials from exposure to infectious aerosols and splashes that may be generated when manipulating materials containing infectious agents, such as primary cultures, stocks and diagnostic specimens. Potentially hazardous aerosol particles are created by any activity that imparts energy into a liquid or semiliquid material, e.g., shaking, pouring, stirring or dropping liquid onto a surface or into another liquid. Other laboratory activities also produce microparticles, e.g., streaking agar plates, inoculating cell culture flasks with a pipette, using a multichannel pipette to dispense liquid suspensions of infectious agents into microculture plates, homogenizing and vortexing infectious materials, and centrifugation of infectious liquids, or working with animals, can generate infectious aerosols. Aerosol particles of less than 5 µm in diameter and small droplets of 5–100 µm in diameter are not visible to the naked eye. The laboratory worker is generally not aware that such particles are being generated and may be inhaled or may cross contaminate work surface materials.

BSCs, when properly used, have been shown to be highly effective in reducing laboratory-acquired infections and cross-contaminations of cultures due to aerosol exposures. BSCs also protect the environment. Modern BSCs are equiped with a high-efficiency particulate air (HEPA) filter to the exhaust system. The HEPA filter traps 99.97% of particles of 0.3 µm in diameter and 99.99% of particles of greater or smaller size. This enables the HEPA filter to effectively trap all known infectious agents and ensure that only microbe-free exhaust air is discharged from the cabinet. Another variant is to direct HEPA-filtered air over the work surface, providing protection of work surface materials from contamination.

Answer 4

Idea of having laminarity is to have sweep all the times when it is working, such that all the parallel moving air molecules maintain the area clean.