Ventilation

There are two main ventilation strategies for hazardous materials or other operations: Local Exhaust and Dilution. Here is a neat You Tube Video https://www.youtube.com/watch?v=Ky8y2jDk6i8 on ventilation.

Vapors tend to rise, or at least settle very slowly, even though the chemical is much heavier than air. The reason is that the difference in density that causes the settling is not the density of the vapor but rather that of the vapor-air mixture. At ten times the TLV, most gas and vapor mixtures are still almost all air. Also, many industrial processes give off heat and convection carries the gas or vapor upward. With the exception of that, the preceding are mostly common sense. Ventilation and hood design should always be done by mechanical PE. The testing and calibration of local exhaust should be by CIH or IH technician under the supervision of a CIH.

Industrial Dilution Ventilation works well if air contaminants: gases, vapors or small particles (D<25um) are of low toxicity and the emissions are uniform in space and time and emission sources are not close to employee breathing zone. Dilution ventilation must be used for mobil sources or situations where hoods are not available. The dilution air must be clean and the HVAC system must maintain appropriate temperature and humidity, otherwise workers will shut them off. Drafts on workers and processes must be considered.

Just a few words about Indoor air quality (IAQ). This is usually not a hazardous waste issue, except that if there are IAQ complaints, attention will naturally focus on the wastes.

Here are the sources of IAQ complaints, based on a NIOSH study of 1300 complaints

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