Fume Hoods

Fume Hood Construction

• Materials of construction used for the interiors of new fume hoods or for the modification of the interiors of existing fume hoods should have a flame spread index of 25 or less when tested according to ASTM E84, UL 723, or NFPA 255 unless the interior of the hood is provided with automatic fire protection.
• Baffles should be constructed so that they cannot be adjusted to materially restrict the volume of air exhausted through the fume hood.
• Ventilation is intended to dilute mixtures of exhaust gases to below a quarter of the lower flammable limit (LFL). Because a spill of liquid hydrogen will likely result in liquid-to-gas expansion that will overwhelm the ventilation, use of liquid hydrogen in a fume hood is not recommended. If liquid hydrogen is used, remote operation is recommended to protect personnel.
• Controls for fume hood services (e.g., gas, air, water) should be located external to the hood and within easy reach.
• In installations where service controls are within the hood, additional shutoffs should be located within 15 m (~49 feet) of the hood and should be accessible and clearly marked.
• A measuring device for hood airflow should be permanently installed on each fume hood and should provide the hood user with constant indication of adequate or inadequate hood airflow.
• Hydrogen leak detection within the hood should be considered where possible.
• Emergency shut-down procedures should be posted and visible.
• An automatic shutdown mechanism should be installed to shut off the flow of hydrogen gas in the event of loss of fume hood air flow if an LFL quantity of hydrogen could accumulate.

Fume Hood Location

• Fume hoods should be located in areas of minimum air turbulence.
• Fume hoods should not be located adjacent to a single means of access to an exit or to high-traffic areas.
• Workstations not directly related to the fume hood activity should not be located directly in front of fume hood openings.