Robert M. Rioux & William A. Elliott, Pennsylvania State University, University Park, PA
Le cappe aspiranti e gli armadi a flusso laminare sono controlli ingegneristici che operano secondo principi simili. Entrambi utilizzano un flusso d’aria costante per prevenire la contaminazione dell’ambiente di laboratorio e dei suoi abitanti. Le cappe aspiranti impediscono alle sostanze pericolose di uscire dallo spazio di lavoro della cappa, mentre gli armadi a flusso laminare impediscono ai contaminanti di entrare nell’area di lavoro dell’armadio.
Le cappe aspiranti sono sistemi di ventilazione progettati per ridurre al minimo l’esposizione a vapori, fumi e particelle pericolosi. Un flusso costante di aria viene aspirato nell’apertura della cappa, limitando la fuoriuscita di vapori, fumi e particelle, e quindi viene estratto attraverso lo scarico. Gli armadi a flusso laminare vengono utilizzati per mantenere un ambiente sterile/pulito facendo scorrere costantemente l’aria filtrata ad alta efficienza con arresto del particolato (HEPA) verso l’esterno, riducendo al minimo l’aria contaminata che entra nello spazio di lavoro dell’armadio. L’aria filtrata HEPA riduce la possibilità che sostanze chimiche o particelle nocive entrino in laboratorio. Un filtro HEPA rimuove il 99,97% o più di particelle da 0,3 μm.
Fume hoods and laminar flow cabinets are useful tools in the laboratory to prevent harm from hazardous materials and to keep a clean working space when using sensitive materials. However, fume hoods and laminar flow cabinets are only effective when used properly. Following simple operating guidelines and performing regular maintenance, fume hoods and laminar flow cabinets can be effective tools in the laboratory.
Fume hoods and laminar flow cabinets are essential pieces of laboratory equipment that prevent hazardous situations and contamination.
In fume hoods and laminar flow cabinets, hazards or contaminants are reduced using airflow. Fume hoods draw in air across a workspace to remove hazardous fumes and fine particles, while laminar flow cabinets blow air through a filter and out to prevent contamination of samples by dust or biological materials.
This video will illustrate how fume hoods and laminar flow cabinets operate, how to use them, and how to perform maintenance.
Fume hoods and laminar flow cabinets operate using laminar airflow, a flow that proceeds in parallel streamlines, which do not cross. Laminar flow, as opposed to turbulent flow, prevents cross-contamination between samples by flowing around objects removing hazardous particles.
Fume hoods have three major parts: the opening face with a sash, the workspace, and the exhaust. The fan in the exhaust draws in air through the opening face, across the workspace, and out through the exhaust. This flow in turn draws out fumes and particles out of the exhaust and away from the laboratory.
At its proper height, the sash restricts the size of the opening, which in turn maintains a high flow of air. This high flow is necessary to prevent the escape of fumes.
Meanwhile, there are two types of laminar flow cabinets, horizontal and vertical. In both, air is drawn through an intake and purifying filter where it is cleared of small particles like dust and bacteria.
A horizontal cabinet directs air horizontally through the workspace. This type of cabinet lessens contamination by hands and gloves, as they are downstream of the samples. However, the airstream does blow directly onto the user, and large objects can obstruct the flow.
In a vertical cabinet, the air is directed from above onto the workspace, then out past a sash. As this type of flow directly contacts the surface of the workspace materials, it helps to prevent cross-contamination. However, the sash can restrict hand movement and the airflow is more turbulent than in a horizontal cabinet.
Now, we will show you how to use these workspaces in a laboratory setting and how to perform basic maintenance.
To use a fume hood safely, always wear appropriate personal protective equipment. Raise the sash up only to the indicated maximum safe working height ensuring sufficient airflow through the hood.
To prevent exposure to harmful fumes or particles, work with only your arms inside the hood, and never let your head enter the workspace. Also, to make sure that the velocity is sufficient throughout the hood, keep the workspace uncluttered, and move all items at least six inches away from the hood face.
When you are done working in the hood, take out all materials. Do not store chemicals in the hood, but rather in a dedicated storage location like a flammables cabinet. Lastly, close the sash to ensure a safer laboratory environment and reduce energy usage.
Perform regular maintenance by testing alarms and flow velocity at the maximum sash height.
If the velocity is low, lower the sash until it is at the required speed. If the sash becomes too low for work to be done at the hood, cease operations until the root of the problem is addressed.
Laminar flow cabinets are commonly used in places where contamination is a concern, like a biology laboratory, so you will need to be careful of contamination by yourself and laboratory air. To prevent contamination, use ethanol to sterilize gloves and any equipment before using the cabinet or opening the sash.
Make sure the sash is not above the maximum allowed height to ensure a sufficient flow of air. Keep the cabinet free from clutter, and make sure objects are placed at least 6 inches from the edge, as that is the area most likely to be contaminated by laboratory air. Also, do not place items in danger of cross-contamination downstream from each other.
When you are done, remove all items from the workspace to prevent clutter and close the sash to prevent contamination. Then, if the cabinet is equipped with a UV-C light, turn it on to disinfect the workspace.
Perform regular maintenance on the laminar flow cabinet. Check for leaks by coating sensitive areas like the sash edges with a soap solution, which will bubble at the site of escaping air.
You’ve just watched JoVE’s introduction to fume hoods and laminar flow cabinets. You should now understand how they work, how to use them, and how to perform maintenance. Thanks for watching!
