A fume hood is the most essential and efficient controlling system in a chemistry laboratory to protect from any type of airborne contaminants. This tool helps us to free ourselves from harmful vapors, gases, or dusts given off by hazardous material used in the lab. The performance of the lab fume hood depends on a sufficient and uniform velocity of air moving through the sash opening.
There are many factors that create a bad effect on performing the activities of chemical hood such as mechanical malfunction, drafts or open doors and windows, and bad operating procedures of the low experienced person using this tool. It helps to create a physical barrier between experiments and the laboratory. A fume hood is essential to prevent chemical spills and run-away reactions.
Fume Hood Working Principle
It is designed in such a way that gases, vapors, and fumes are captured in its area and removed from the work area easily at a constant volume. An exhaust fan is generally installed in lab buildings which pulls air and airborne contaminants through connected ductwork and removes these contaminants from our atmosphere.
The baffles and slot in this tool direct the air and, can be adjusted to flow. It must be remembered that baffles should be free from becoming blocked, by excessive material storage or equipment. The airfoil around the hood face helps airflow enter the hood by removing sharp curves to reduce turbulence.
The advanced type lab fume hood has the ability to filter the air to remove toxic fumes and then return the air to the lab. It consists of gauges or alarms that warn us about the user of low airflow and various exposures to hazardous fumes.
Fume Hood Instrumentations
Sash: It is a sliding door of this tool that helps to adjust the amount of airflow into the hood
Bypass Grille: It helps to produce additional airflow that varies with the sash height and controls the face velocity.
Fixed Slot: This slot is very important for the proper distribution of airflow across the hood face.
Airfoil: It is a streamlined airflow that prevents eddies that carry vapors out of the hood.
Work Surface: It is the hood surface area which is recessed to contain spills within the hood
Rear Baffle: It is a movable part that is used for creating a uniform airflow across the hood opening
Adjustable Slot: It is a movable slot that is used to produce uniform airflow across the hood opening
Screen: It helps to prevent the materials from blocking and creates a uniform airflow across the hood opening.
Fume Hood Types
Bypass fume hood: This fume hood is very used which provides a bypass mechanism located above the sash face opening that controls the face velocity as the sash is lowered at or near the closed position. There is no change that occurred at the time of closing of the sash.
Constant Air Volume fume hood: The amount of exhausted air does not change with time during the opening of the sash in this type of chemical fume hood.
Floor-Mounted fume hood: This special type of lab chemical hood is generally used in a large amount of working space area. It should avoid walking into a floor-mounted fume hood during operation and containing hazardous materials unless PPE is worn.
Perchloric Acid fume hood: This fume hood is constructed with glass, plastic, or stainless steel and the compatible with perchloric acid and its byproduct because this acid creates an explosion when heated above ambient temperatures. It consists of a water wash-down system for removing the perchlorate crystals from all interior surfaces, including the ducts, fans, and stack.
Fume Hood Maintenance
The laboratory experiments should be performed at least 6 inches inside the chemical lab hood. It should avoid any types of rapid movements, such as opening & closing doors. It is the most important tip that the sash should be kept as low as possible and closed when the hood is not in use. It must be remembered that the equipment and chemicals should not be stored permanently inside the fume hood.
It can monitor the flow of air periodically. Large quantities of perchloric acid, hydrochloric acid, and hydrofluoric acid should not be used in this tool for its durability. This tool must be tested annually by authorized persons to check its proper activities.
Fume Hood Applications
The fume hood is a popular tool in analytical chemistry labs for removing toxic gases such as sulfur dioxide gas. It is used very much in that experiment which deals with chemicals that easily sputter out during heating. The flammable chemicals are heated easily in this tool. The volatile chemicals and various carcinogens are handled easily within this enclosure system.
References
1.Mullins, E. (2003). Statistics for the quality control chemistry laboratory. Royal Society of Chemistry.
2.Hibbert, D. B. (2007). Quality assurance in the analytical chemistry laboratory. Oxford University Press.
