| If you’re a fan of the new hit HBO series, Boardwalk Empire, then you know a lot about the effects of Prohibition. But did you know that Prohibition is responsible for the creation of mixed drinks? Until then, people drank their liquor straight. Then along came Prohibition, mob rule, and the desire to keep the booze, including some with questionable origins, flowing. This booze didn’t taste so good, and the addition of a sugary beverage to it, that is, diluting it with soda or juice, made it a lot easier to go down. By the time Prohibition was repealed in 1933, the mixed drink had taken a firm foothold in American society.
Most adults are aware of the fact that liquor, in excess, is toxic to the body. Too much of it, and the liver, which acts as a filtration device, itself becomes toxic. When that happens, poor health will follow. The same principle applies to air within a building. If it becomes thick with toxic fumes or potentially flammable vapors, indoor air quality will suffer. But if you infuse fresh air into the environment, the toxic load is diluted, making the environment habitable and safe. This addition of fresh air is called, appropriately enough, dilution ventilation. Now, the easiest way to create a dilution ventilation system is to open a window. Trouble is there often isn’t enough natural airflow to do much good. But if you step up the effort by introducing a mechanical ventilation system, complete with blowers and ductwork, the need to crack open a window becomes obsolete. By exchanging bad air for good and introducing a continual flow of fresh air, toxicity is diluted and its effects are minimized, much like the bathtub gin of Prohibition was improved by the addition of soda. The chance of fire or explosion is reduced as well. There are however limits to what dilution ventilation can accomplish. If contaminants are highly toxic or extremely flammable, then this type of ventilation system is not going to do much good. This is a situation where extremely high air flows would be required, and this is often impractical both from a cost and comfort standpoint. Imagine having to work inside a wind tunnel? In situations like these a local exhaust ventilation system is better suited to do the job, and we’ll see how those work next week. _____________________________________________
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Posts Tagged ‘dilution ventilation’
Industrial Ventilation – Dilution Ventilation
Sunday, April 3rd, 2011
Industrial Ventilation
Sunday, March 27th, 2011| On a hot, sticky day, what price would you pay for a cool breeze? Imagine for a moment that it’s 90 degrees in the shade and humidity is 85%. There are few human beings that wouldn’t consider this uncomfortable weather, although I have some die hard neighbors who rarely close their windows during the summer to engage the air conditioning, a rather recent modern convenience. My mom told me stories of how it was common in the 1940s for entire Chicago neighborhoods to head to Lake Michigan, spread a blanket, and sleep on the beach to keep cool on the hottest nights. As for myself, I remember being really happy when Dad broke down and finally purchased a window air unit. It was as big as a small refrigerator and took two men to lift. It was loud and drew so much power it frequently “blew the fuse.” It was so much nicer when central air conditioning came along a few years later and we could finally retire that old clunker.
Ultimately, it’s ventilation that makes air conditioning work, the principle here being a continuous circulation of air, exchanging hot for cooled. If you’ll remember, hot air gives up its heat to coils containing coolant, and the newly cooled air is released back into the room. In addition to cooling, another major function of ventilation is to remove odors and refresh the air. Everyone likes a fresh smelling home, but even more importantly, proper ventilation reduces the concentration of contaminants in the air, things which tend to make us sick, like mold. That’s why many states’ building codes require whole house air ventilation systems to be installed in new homes. In industrial settings ventilation performs the same functions, but it’s necessary for other reasons as well. Industrial facilities often house processes that create airborne toxins and other contaminants. These byproducts of manufacturing can be dangerous if allowed to collect unchecked within the confines of a building. Air containing certain concentrations of contaminants, such as vapors emitted by paints and solvents, can ignite, resulting in fire or explosion. For safety of both workers and equipment, fresh air must displace air contaminated with fumes and dust. There are three types of ventilation that can be found in industrial facilities. These include indoor air quality ventilation, dilution ventilation, and local exhaust ventilation. Indoor air quality ventilation provides freshly heated or cooled air to buildings as part of the normal heating, ventilating and air conditioning system, much like we have in our own homes. Dilution ventilation gets its name from the fact that it dilutes contaminated air by displacement, the blowing in of clean air and exhausting of dirty. The last type of ventilation, local exhaust ventilation, captures contaminated emissions at or near the source and exhausts them directly outside. Depending on the type of industrial application one, two, or all three of these ventilation types may be employed to keep air quality safe. Next week we’ll discuss dilution ventilation in detail, followed by local exhaust ventilation, and we’ll gain a better understanding of how they are used to protect worker health and safeguard property. _____________________________________________ |
