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; and
- Portable or mobile emission sources are to be controlled
Local exhaust ventilating is appropriate when: