Question 1

What is laminar flow and how does it work in laboratory hoods?

Accepted Answer

Laminar flow is the streamlined, undisrupted flow of air in parallel layers. Unlike turbulent flow, laminar flow allows air to flow around objects within the hood, maintaining sterility of the work environment and containing noxious chemical fumes. This principle is fundamental to all hood operations.

Question 2

What are the main differences between horizontal and vertical laminar flow hoods?

Accepted Answer

Horizontal flow hoods have filtered air intake flowing horizontally from back to front toward the user. Vertical flow hoods pull filtered air vertically away from the user, with exhaust filtered as it exits. Both designs maintain work environment sterility, but vertical flow provides better user protection from airborne hazards.

Question 3

What basic components do all laboratory hoods share?

Accepted Answer

All hoods include a window sash, a sliding protective glass barrier shielding against splashes and fumes. They have a non-porous work surface, typically stainless steel, an air intake where air enters, and an exhaust. Many include control panels for adjusting air intake and lights, and some feature UV disinfection capabilities.

Question 4

How should you prepare a hood before beginning tissue culture work?

Accepted Answer

Spray the hood surface with 70% ethanol to disinfect it; the solution quickly evaporates leaving no residue. Spray each object with 70% ethanol as you place it in the hood to maintain a clean environment. Wear appropriate personal protective equipment including gloves, goggles, and a mask as necessary for the procedure.

Question 5

When should you use a fume hood versus a laminar flow bench?

Accepted Answer

Use a fume hood for procedures producing toxic fumes or involving corrosive chemicals, such as fixation, tissue processing, and histological sample preparation for light microscopy. Fume hoods protect the user but not the experimental environment. Laminar flow benches protect the experiment but not the user, making them suitable for sterile work with non-hazardous samples.

Question 6

What is the purpose of a tissue culture hood or biosafety cabinet?

Accepted Answer

Tissue culture hoods and biosafety cabinets protect both the user and the experiment. All air is high-efficiency particulate air (HEPA) filtered as it enters and exits the cabinet, maintaining sterility of the experimental workspace. Many are equipped with vacuum aspiration systems for aspirating tissue culture media, and each has a specific biosafety level rating.

Question 7

What safety precautions should you follow when working with hood UV lights?

Accepted Answer

Never leave UV lights on while anyone is in the lab or using the hood. UV exposure can cause retina damage, skin burns, and increased cancer risk. UV lights should only be used to disinfect the hood unit when the space is unoccupied and all personnel have left the laboratory.

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