Prudent Practices for Handling Hazardous Chemicals in Laboratories1981

Prudent Practices for Handling Hazardous Chemicals in Laboratories（1981） u 4 -12 (6 -12, 1995) air changes / hour u 10 -20 air changes / hour for animal care facilities u 6 air changes / hour for storage facilities of flammables u. If is thoroughly mixed - 6 air changes/hour - 98. 4% of original air being exchange

EH&S Laboratory Design Criteria （2000, Cornell university） u Occupied wet lab--8 to 10 air changes per hour minimum (depending upon hazards in the room—more may be needed) u Unoccupied u Occupied wet lab--6 air changes per hour minimum. dry lab--8 to 10 air changes per hour minimum. u Unoccupied dry lab--6 air changes per hour minimum

Fume Hood-Control System

Fume Hood

Fume Hood-Biological Safety Cabinets

Fume Hood-Fully or Partly Open

Fume Hood-Bypass or Add-air

Fume Hood - Comparing Control Approaches u Constant Volume Control u Two-stage Control u Variable Air Volume Control u Usage Based Control

Fume Hood(一)

Fume Hood(二)

Fume Hood(三)

Fume Hood(四)

Fume Hood - Demonstration

Fume Hood - Demonstration

Fume Hood - Ductless Filtering u. Filter u. Gas or Vapor Handled u. Detect-detector, color coded reactive tubes u. AFNOR 211 NF X 15 -

Prudent Practices in the Laboratory Handling and Disposal of Chemicals (1995） u Face velocity 80 -100 u 100 -120 fpm (40. 7 -50. 8 cm/sec). fpm for very high toxicity substances or outside influences adversely affect hood. u 75 -125 fpm --NIOSH Guide u At least one face velocity measurement per square feet. -ASHRAE 110 u The (standard deviation) of the average velocity profile at each point don’t exceed 20% of the mean, the average of velocity at each traverse point(turbulence) don’t exceed 15% of the mean face velocity.

EH&S Laboratory Design Criteria （2000, Cornell university） u. All new hood installations should be designed to provide a full open face velocity of 100 f. p. m. , +/- 20 f. p. m. over the lifetime of the system. u. All center points of a 3 x 3 grid at the face of a hood should have velocity readings within +/- 15 f. p. m. of each other.

EH&S Laboratory Design Criteria Hood placement（2000, Cornell university） u Hoods should be placed 10 feet from any doors (except emergency doors) u Hoods should be placed as far away from each other as possible u Corner locations should be avoided u Hoods should be placed so as to avoid pedestrian traffic immediately in front of the hood. u Large pieces of equipment should not be positioned in front of a hood. u Hoods should not be placed where they would face each other across a narrow isle. u Hoods should not be placed near windows or very cold equipment as this could cause turbulence at the face of the hood.

Fume Hood Performance l. Face velocity (Size, Sash, Shape. . ) l. Exhaust ports, back baffle, bypass or auxiliary air. l. Adjacency to traffic, supply air diffuser, windows and doors (size and location). l. Researcher’s breathing zone

Fume Hood Performance Criteria -method of test(ASHRAE 110) l. Face velocity test. l. Flow visualization test. l. Large volume flow visualization l. Tracer gas test. l. Sash movement test.

USER'S GUIDE TO FUME HOODS Good Work Practices and Changes You Can Make（1998, Cornell university） u. Keep the Sash Down u. Have an Airfoil Installed u. Use an Airflow Indicator u. Keep Laboratory Doors and Closed u. Limit Traffic u. Reduce Clutter u. Work Far Into the Hood. Windows