Basic Documentation

Laboratory Ventilation Codes and Standards
Siemens Industry, Inc. 140
Topic Requirement(s) Commentary
Stack Height
and
Discharge
Location
California OSHA – Division of Occupational Health & Safety (DOSH) Subchapter
7. General Industry Safety Orders, Group 16. Control of Hazardous Substances,
Article 107. Dusts, Fumes, Mists, Vapors and Gases
5154.1. Ventilation Requirements for Laboratory-Type Hood Operations:
(1) The air outlet from every dust separator/collector and the dusts, fumes, mists,
vapors or gases collected by an exhaust or ventilating system shall discharge to the
outside atmosphere, provided that the exhaust system shall discharge to the outer
air in such a manner that it will not cause a harmful exposure in any accessible
workplace. Collecting systems which return air to work areas may be used if
contaminants which accumulate in the work area do not result in harmful exposure to
employees.
(2) The air exhausted from blast-cleaning equipment, grinding, buffing, polishing
equipment and all other equipment requiring exhausting of dust or particulate shall
be discharged through dust-collecting equipment. Dust and refuse discharged from
an exhaust system shall be disposed of in such a manner that it will not result in
harmful exposure to employees.
(4) Exhaust stacks shall be located in such a manner with respect to air intakes as to
preclude the recirculation of laboratory-type hood emissions within a building. To
protect employees on the roof, any one of the follow methods shall be utilized:
(A) Chemical treatment, absorption on activated charcoal, or scrubbers;
(B) Dilution of toxic materials below prescribed exposure limits prior to discharge;
(C) Locked gates, doors or other equivalent means acceptable to the Division which
prevent employee access to exhaust stack discharge areas while hoods are in
operation unless personnel are provided with appropriate respirators and other
personal protection; or
(D) Exhaust stacks extending at least 7 feet above the roof and discharging vertically
upward. Where rain protection is desired, high velocity discharge or concentric-duct,
self-draining stacks or equivalent may be used. Rain caps which divert the exhaust
toward the roof are prohibited.
(5) Where emissions from the exhaust stack are likely to cause harmful exposure to
employees, an effective air cleaning system shall be provided. Where virulent
pathogens are likely to be released in the hood, incinerators or equally effective
means of disposal shall be provided in the exhaust system to prevent employee
exposure.
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When there are nearby buildings, complex
architectural features and irregular terrain, it
may not be possible to reliably establish the
necessary height of a stack by mathematical
calculations. In such instances scale modeling
of the facility and surrounding area and wind
tunnel testing might be the best way to provide
a realistic indication of the necessary stack
heights and location.
Stacks should never have a rain cap or
anything else that adversely affects the
creation of an unobstructed vertical discharge
plume comprised of exhaust and entrainment
air.
Also see Appendix 3 - ANSI/AIHA Z9.5-2003,
which provides comprehensive information on
Selecting Laboratory Stack Designs.