Use Of Hoods

General Principle

All chemical laboratories are equipped with hoods. The exact location can be taken from these maps. A hood is a transparent working space that can be isolated  from the lab environment by means of a sash that can be raised and lowered. Through an upward air flow in the hood, a slight underpressure  is created that prevents fumes from escaping into the adjacent laboratory.
All hoods can be vented from the bottom also to remove fumes heavier than air

Procedure

  • The sash shall be fully closed to its lowest position whenever the hood is not in use.
  • Keep the sash at all times in the lowest position possible when manipulations are carried out. At the end of the experiment or whenever the experiment no longer needs manual intervention; fully close the sash again.
  • Handle volatile or toxic solvents exclusively in the hood.
  • Carry out any vaporization of solutions that generates fumes other than water vapor in the hood.
  • Observe all experimental work from the outside. Never place the head in the hood in the course of an experiment.
  • Keep the hood clean at all times. This holds especially when handling very hazardous carcinogenic, teratogenic and mutagenic products. Clean the bench upon completion of the experiment. Use a protective coating layer, such as Benchkote, if possible. The layer can be disposed of as Small Chemical Waste.
  • A hood is a collective safety device for the people handling hazardous products. As all vented fumes end up in the environment, emission of volatile products, and especially of halogenated organic compounds, should be reduced as much as possible by keeping recipients closed and by condensing fumes that escape during evaporation or distillation experiments as much as possible. Most organic compounds are absorbed by charcoal. Acid fumes can be neutralized in a scrubber. Mercaptans are a case in itself: their odor can result in gas leak alerts. Avoid accidental draining off in the hood's sink by placing the experimental set-ups in trays.
  • A hood may not become a storage facility for hazardous products.
  • A functional hood features an air flow of about 0.5 m/s at a sash opening of 35 cm as marked by the blue sticker. Notify your Specialized HSE Contact in case of doubt. An air flow meter is available to verify proper operation of the hood.