Last month I posted Exhaust Ventilation for Flammable Atmospheres and “Safe Locations” to explain the hazards of not controlling our flammable vapors associated with the required exhaust ventilation. I received several comments and questions on that article regarding the normal process of venting hazardous materials and how to best define a “safe location” for these process vents (vs. the exhaust ventilation).
I turn to NFPA 30 to help with defining a “safe location” for these process vents. NFPA states the following:
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A “safe location” should be selected as the location of a vent discharge to minimize the potential for ignitible vapors to travel to a source of ignition after discharge from the vent. Electrical equipment that does not meet the requirements for hazardous locations can serve as an ignition source.
The Technical Committee advises that vent discharge locations should consider such factors as the following: (1) Characteristics of the exhausted material (vapor density, toxicity, the velocity of discharge, etc.) (2) Proximity to potential ignition sources (3) Building openings such as doors, windows, air intakes, and so forth (4) Dispersion characteristics (distance to discharge within the flammable range, the direction of discharge, atmospheric conditions, and the influence of building and neighboring buildings on discharged vapors) (5) Likelihood of vapor accumulation following discharge, such as accumulation under building eaves (6) Likelihood of sufficient discharge volume to allow an ignitible concentration to reach an ignition source |
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