Laboratory Fume Hoods- a sophisticated ventilation unit

A laboratory fume hood, often known as Fume closet, is a unique ventilation device, used in different laboratories. This device is designed very smartly to limit exposure to potentially dangerous and toxic vapors, specks of dust, and hazardous fumes.  A laboratory fume hood is a piece of standard large-sized lab equipment that encloses five different sides of a working area. Generally, the bottom of this fume hood remains at a working height. 

There are two significant categories of laboratory fume hoods available in the market- ducted fume hoods and ductless fume hoods. However, the operating principle is the same for both varieties. The air usually gets drawn inside the machine, from the exposed side of the working area. This air is then either expelled outside the building or run through efficient filters and fed inside the working space. 

Potential uses of laboratory fume hoods- The primary functions

As mentioned earlier, this instrument gets into use in laboratories as a ventilation unit; this also provides many other benefits.

· It provides extreme protection to the user from inhaling toxic fumes and hazardous gases emitted during laboratory experiments. 

· It also offers ultimate protection to the ongoing experiment or the materials used in the experiments. 

· It leaves back a healthier, cleaner, and safer ambiance to work with, clearing off all potential hazardous pollutants.

Besides these, primary functionality,  laboratory fume hoods are beneficial for other secondary uses as well. Among the secondary functions, the most important of them is the containment of probable spills, protection towards any explosion or accidents inside the working area. It provides an overall safe space to carry on with the experiments. 

The basics of laboratory fume hoods

A laboratory fume hood is generally set back inclined to the walls of the working area. To cover up the exhaust ductwork panels, it is often fitted with the infills. The recessed shape of this working unit hinders proper lighting, and room lights fall short of adequate illumination. Many fume hoods are equipped with internal lights along with vapor-proof coverings to cope with this illumination problem. The frontal side is generally a glass window that can quickly move up and down, working on a counterbalance mechanism. When it comes to educational purposes and laboratory experiment works, the side walls are composed of glass. This offers a see-through vision for the people working in the laboratory. 

Laboratory fume hoods are available in quite a few different sizes. Starting from 1000mm, the size of the device can range up to 2000mm. The depth of the unit ranges from 700-900 mm, and the height varies between approximate ranges of 1900- 2700 mm. This large area can comfortably accommodate a single to three users at a time. While dealing with extremely hazardous substances, a protected glovebox is often seen to be used. It completely cuts off all physical contact of the operator with all working tools and elements. 

There are different types of liner materials used in a laboratory fume hood. It can be a phenolic resin, epoxy resin, fiber-reinforced plastics, or superior quality polypropylene. Stainless steel is also often used to render heat resistance. The control panels of the laboratory fume hoods are very sophisticated. They are sometimes main-powered and perform various functions. It includes warning of large opening at the frontal unit or low airflow. It also allows the switching on and off of the internal lights and exhaust fans. As per requirements, additional features can anytime be added to the working unit, to increase the efficiency. 

Types- Ducted and Ductless varieties

The fume hoods used for industrial purposes are mainly ducted ones. There is a wide array of a ducted variety of laboratory fume hoods. In most cases, the heated or cooled air is drawn inside from the lab space into the fume hood. This conditioned air is then dispersed to the outside of the working area via fitted ducts. These fume hoods form the only method of ventilation in laboratories. Since recirculation of the laboratory air to the rest of the space is not facilitated, units handling the non-laboratory areas are kept segregated from lab units. 

In the case of ductless or recirculating fume hoods, an additional fan is fitted at the top of the fume hood. Sometimes this fan is also found attached just beneath the worktop. Air gets sucked in from the laboratory space, usually from the frontal exposed window. This sucked in the air content then passes through the high-efficiency filters and runs back to the lab area. This recirculating feature ensures the flow of treated air throughout the entire working space. However, the ductless varieties work harder with the fan fitted above the hood, and thus, end up creating a lot of noise.

Moreover, this variety falls under recommendation only when the hazard category is well identified and does not tend to change in composition. Be it a ducted unit or a ductless one, all classes of laboratory fume hoods work with a massive volume of conditioned air always. Thus, energy consumption is quite high in these lab units.