• Workplaces with certain specific types of operations must supply ventilation in the form of general exhaust ventilation or local exhaust ventilation, depending on the type of emission.

The Occupational Safety and Health Administration (OSHA) requirements generally apply to workplaces that have specific types of operations.

According to the OSHA Technical Manual, general exhaust ventilation (dilution ventilation) is appropriate when:

• Emission sources contain materials of relatively low hazard. (The degree of hazard is related to toxicity, dose rate, and individual susceptibility).
• Emission sources are primarily vapors or gases, or small, respirable-size aerosols (those not likely to settle).
• Emissions occur uniformly; emissions are widely dispersed.
• Moderate climatic conditions prevail; heat is to be removed from the space by flushing it with outside air.
• Concentrations of vapors are to be reduced in an enclosure.
• Portable or mobile emission sources are to be controlled.

Local exhaust ventilating is appropriate when:

• Emission sources contain materials of relatively high hazard.
• Emitted materials are primarily larger-diameter particulates (likely to settle).
• Emissions vary over time.
• Emission sources consist of point sources.
• Employees work in the immediate vicinity of the emission source.
• The plant is located in a severe climate.
• Minimizing air turnover is necessary.