Basic Documentation

Laboratory Ventilation Codes and Standards
Siemens Industry, Inc. 22
Topic Requirement(s) Commentary
Face Velocity
U.S. OSHA, 29 CFR, Part 1910, Occupational Safety and Health Standards,
Subpart Z, Toxic and Hazardous Substances,1910.1450,C4(g):
General air flow should not be turbulent and should be relatively uniform throughout
the laboratory, with no high velocity or static areas; airflow into and within the hood
should not be excessively turbulent; hood face velocity should be adequate (typically
60-100 lfm). [“lfm” stands for linear feet per minute or simply ‘feet per minute’.]
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:
(c) Ventilation Rates. Laboratory-type hood face velocities shall be sufficient to
maintain an inward flow of air at all openings into the hood under operating conditions.
The hood shall provide confinement of the possible hazards and protection of the
employees for the work which is performed. The exhaust system shall provide an
average face velocity of at least 100 linear feet per minute with a minimum of 70 lfm at
any point, except where more stringent special requirements are prescribed in other
sections of the General Industry Safety Orders, such as Section 5209. The minimum
velocity requirement excludes those measurements made within 1 inch of the
perimeter of the work opening
The face velocity required by subsection (c) should be obtainable with the movable
sashes fully opened. Where the required velocity can only be obtained by partly
closing the sash, the sash and/or jamb shall be marked to show the maximum
opening at which the hood face velocity will meet the requirements of subsection (c).
Any hood failing to meet requirements of subsection (c) and this paragraph shall be
considered deficient in airflow and shall be posted with placards, plainly visible, which
prohibit use of hazardous substances within the hood
National Fire Protection Association, Standard NFPA 45, 2011
8.4.6 Chemical fume hood face velocities and exhaust volumes shall be sufficient to
contain contaminants generated within the hood and exhaust them outside of the
laboratory building.
8.4.7 The hood shall provide containment of the possible hazards and protection for
personnel at all times when chemicals are present in the hood.
A.8.4.7 Laboratory fume hood containment can be evaluated using the procedures
contained in ASHRAE 110, Method of Testing Performance of Laboratory Fume
Hoods. Face velocities of 0.4 m/sec to 0.6 m/sec (80 ft/min to 120 ft/ min) generally
provide containment if the hood location requirements and laboratory ventilation
criteria of this standard are met.
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Face velocity is defined as the average
velocity of the air entering a hood
perpendicular to the face opening in the plane
of the sash opening. A measurement of the
average face velocity requires that either an
airflow measurement traverse be made in the
Fume Hood Face Opening or the total
exhaust airflow must be measured and then
divided by the face opening area.
These face velocity requirements apply to all
types of fume hoods regardless of physical
arrangement (that is, bench top, walk-in, etc.)
or application of the hood (general chemistry,
perchloric acid, radioisotope, etc.).
In addition to face velocity, room design, room
air cross currents (cross drafts), personnel
movement, and safe user practice all have a
major impact on a hood’s ability to provide
effective fume containment. Even though a
fume hood may have a face velocity at or
slightly above the recommended level, it may
not provide adequate containment due to the
impact of one or more of the foregoing
factors. (Also these the next section, Room
Air Cross Currents.)