Hoods: Laminar Flow & Fume

  1. Exhaust Fume Filtration

    Exhaust Fume Filtration
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    Activated charcoal, the most common purification filtration medium, adsorbs chemicals with a molecular weight above 30 and a boiling point above 60°C. Carbon filters are also effective with many other chemicals because of their particular molecular structure.

    Adsorption takes place in the active filter zone, the small cross-section of the filter bed in which the material to be removed comes in contact with the filtering medium (see illustration). This active filter zone moves upward as the filter becomes saturated. When it reaches the filter's top surface, there is an initial breakthrough by the contaminant gas; thereafter the percentage of contaminant gas that escapes filtration increases until total

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  2. Under the Microscope: What are Hoods?

    Under the Microscope: What are Hoods?

    Whether you’re using a laboratory hood to limit exposure to chemical fumes or you require a particle-free work environment, all components of your hood work in tandem to attain optimal functionality. Hoods are enclosures, sometimes called work benches, work stations, or cabinets, that either blow filtered air down onto the work surface (positive pressure) or exhaust filtered air to the outside (negative pressure), based on the nature of the application. Below is a guide to understanding the different components of your cleanroom hood.

     

    Sash/Shield

    The sash or shield, located on the face of your hood, is a transparent panel that shields internal samples from contamination while providing some protection to the outside environment. For personnel to reach inside the hood and perform work, the sash is raised. When the sash is completely closed, UV sterilization can be accomplished safely. Since ope

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  3. Horizontal vs Vertical Laminar Flow Hoods

    Horizontal vs Vertical Laminar Flow Hoods

    A laminar flow system is a vital concept in the control of particulate contamination. Laminar airflow is defined as air moving at the same speed and in the same direction, with no or minimal cross-over of air streams (or “lamina”). By contrast, turbulent flow creates swirls and eddies that deposit particles on surfaces randomly and unpredictably. Most contamination-sensitive environments such as dust-free hoods require laminar flow because it predictably sweeps particles in a uniform direction, from the cleanest area under the hood (the filter face) to the exit area, which is generally the sash opening or vents along the back or bottom of the hood. This design ensures that the cleanest (and most germ-free) area will always be the upstream area closest to the filter face. Work

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