1. New hoods can be mounted above a chemical storage cabinet, provided that the cabinet meets the Uniform Fire Code requirements for construction.
Good Practice per Stanford University EH&S
Recommend that solvent storage not be located under the laboratory fume hood, as this location is where fires are most likely to occur in laboratories.
2. Type 316 stainless steel should be used for all parts of the fume hood system ventilation duct as long as compatibility is maintained.
Good Practice per Stanford University EH&S
This material affords good, general corrosion, impact and vibration resistance.
3. Fume hood interior surfaces shall be constructed of corrosion resistant, non-porous, non-combustible materials such as type 316 stainless steel, and should be smooth and impermeable, with rounded corners. These materials shall have a flame spread index of 25 or less when tested in accordance with NFPA method 255, Standard Method of Test of Surface Burning Characteristics of Building Materials.
NFPA 45, Chapter 6-8.1.1, 6-11.2, 6-11.6
NFPA 99, 5-4.3.3
ANSI/AIHA Z9.5-1992, 5.12
Type 316 stainless steel (SS 316) is specified to avoid corrosion, thereby extending fume hood life. Splashes of liquid containing radioactive materials can be easily cleaned when hoods are constructed of non-porous materials such as stainless steel. Perchloric acid digestion over time may result in the condensation and consequential formation of perchlorate crystals, which in large quantities pose an explosion hazard, especially if combined with organic chemical condensate.
4. Hood inserts are only permitted for radioactive iodination procedures specifically approved by the Stanford Radiation Safety Officer.
5. Laboratory hoods shall be provided with a means of containing minor spills.
NFPA 45, Chapter 6-9.1.3
ANSI/AIHA Z9.5, 5.2
The means of containing minor spills might consist of a 6.4-mm (1⁄4 in.) recess in the work surface, use of pans or trays, or creation of a recess by installing a curb across the front of the hood and sealing the joints between the work surface and the sides, back, and curb of the hood.
6. There must be a horizontal bottom airfoil inlet at the front of the hood.
ANSI/AIHA Z9.5, 5.2
The air foil at the front of the hood floor assures a good sweep of air across the working surface toward the back of the hood. This minimizes the generation of turbulents or eddy currents at the entrance to the hood.
7. Adjustable baffles with horizontal slots must be present in the fume hood interior at the back and top.
ANSI/AIHA Z9.5, 5.2
Locating the slots in this manner will attain reasonably uniform face velocity under different conditions of hood use as related to heat sources, size, and configuration of equipment in hood.
8. Before a new fume hood is put into operation, an adequate supply of make up air must be provided to the lab.
Good Practice per Stanford University EH&S
A fume hood exhausts a substantial amount of air. For this reason, additional make up air must be brought into the room to maintain a proper air balance.
9. Face Velocity:
Laboratory fume hoods shall provide a minimum average effective face velocity of 100 feet per minute (fpm), with a minimum of 70 fpm at any point.
Ref: 8 CCR 5154.1(c)
10. Certification: See Stanford University’s laboratory fume hood performance and certification protocol at:
Fume Hood Testing and Performance Standards (LVMP Appendix 10.2.1)
11. Where the required velocity can 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.
CCR, Title 8, Section 5154.1(e)(1)
12. An airflow indicator shall be provided and located so that it is visible from the front of the fume hood.
CCR, Title 8, Section 5154.1(e)(3)
NFPA 45, Chapter 6-8.7.1
ANSI/AIHA Z9.5-1992, 5.8
Follow manufacturer’s procedures for calibration of air flow indicator during installation. Follow manufacturer’s schedule for periodic calibration and maintenance parameters thereafter. Performance criteria for various airflow indicators are as follows:
o Kim Wipes: Shows inward flow.
o Magnahelic Gauges: Mark on gauge inches water read when average face velocity at 100 fpm.
o FPM Readout: Average readout is 100 fpm.
o Audio/Visual Alarms: Go into alarm mode if average face velocity drops to 80 fpm.
13. Baffles shall be constructed so that they may not be adjusted to restrict the volume of air exhausted through the laboratory hood.
NFPA 45, Chapter 6-8.1.2
14. Fans should run continuously without local control from hood location and independently of any time clocks.
Good Practice per Stanford University EH&S
If users have ability to shut off hoods or control their use with a time clock, there is a potential for users to conduct research in a hood that is not operating.
15. For new installations or modifications of existing installations, controls for laboratory hood services (eg., gas, air, and water) should be located external to the hood and within easy reach.
NFPA 45, Chapter 6-8.5.1
16. Shutoff valves for services, including gas, air, vacuum, and electricity shall be outside of the hood enclosure in a location where they will be readily accessible in the event of fire in the hood. The location of such a shut-off shall be legibly lettered in a related location on the exterior of the hood.
NFPA 99, Chapter 5-4.3.6
17. Laboratory hoods shall not have an on/off switch located in the laboratory. Exhaust fans shall run continuously without direct local control from laboratories.
Good Practice per Stanford University
18. Drying ovens shall not be placed under fume hoods.
Good Practice per Stanford University
