Engineering Expert Witness Blog

       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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