Select the true statement, with reference to the Laminar Air flow

Question

Accepted Answer

The correct option is 1:
A Laminar Air Flow cabinet (or biological safety cabinet) is designed to create an aseptic work environment, which is absolutely essential for procedures like tissue culture, microbial plating, and media preparation where contamination must be rigorously avoided. The central mechanism for achieving this sterility is the High-Efficiency Particulate Air (HEPA) filter. The statement "Air is sterilized using HEPA filters" is true because the air entering the work area is forced through these filters. HEPA filters are composed of a dense mat of randomly arranged glass fibers that are highly effective at trapping airborne particulates, including dust, pollen, molds, and most importantly, bacterial cells and fungal spores. By physical trapping, they effectively remove these contaminants, thereby sterilizing the air before it flows over the work surface in a smooth, non-turbulent (laminar) stream, protecting the materials being handled. A certified HEPA filter is rated to remove at least 99.97% of all airborne particles that are $0.3$ micrometers ($\mu$m) in diameter, which covers the vast majority of microbiological contaminants.

The incorrect option is 2:
The statement "The UV radiations are used to sterilize while working on the bench" is false due to both safety and efficacy reasons. While a Laminar Air Flow cabinet is typically equipped with a short-wave ultraviolet (UV) lamp, this lamp is intended only for the *preliminary sterilization* of the cabinet's internal surfaces *before* work begins, and it must be turned off while the operator is actively working. UV radiation, particularly the germicidal C-band, is hazardous; direct exposure to the operator's skin and eyes can cause serious damage, including cancer and corneal burns. Furthermore, UV light cannot penetrate surfaces or shadows, meaning it would be ineffective at sterilizing materials in use or the operator's hands during an ongoing procedure. The primary sterilization of the air is, and must always be, carried out by the HEPA filter.

The incorrect option is 3:
The claim that "It is primarily used to sterilize the culture media and glassware" is incorrect because the Laminar Air Flow cabinet is designed to create a sterile *working space*, not to sterilize the materials themselves. The culture media is typically sterilized using an Autoclave (moist heat under pressure), and glassware is sterilized using a Hot Air Oven (dry heat). The cabinet's role is to ensure that *after* these materials have been sterilized, they do not become contaminated when they are opened, mixed, or manipulated on the bench. Therefore, its primary function is *aseptic manipulation*, not bulk sterilization of media or equipment.

The incorrect option is 4:
The statement that "The principle of sterilization is the same for both autoclave and laminar air flow" is definitively false as the underlying principles are completely different. The Laminar Air Flow cabinet achieves sterilization through **filtration**, which is a physical process that *removes* microorganisms from the air based on particle size. In stark contrast, the Autoclave achieves sterilization through **moist heat (steam under pressure)**, which is a physical process that *destroys* microorganisms by denaturing and coagulating their proteins. The cabinet prevents contamination from the environment, while the autoclave eliminates contamination inherent to the materials. They are complementary methods, but their mechanisms of sterilization are fundamentally distinct.