Chemical Hygiene Plan - Queensborough Community College ...

• If toxic, flammable, or otherwise hazardous chemicals are evolved from the oven, then
only use ovens with a single pass through design where air is ventilated out of the lab and
the exhausted air is not allowed to come into contact with electrical components or
heating elements.
• Heating flammables should only be done with a heating mantle or steam bath.
When using heating baths, these additional guidelines should be followed:
• Heating baths should be durable and set up with firm support.
• Since combustible liquids are often used in heat baths, the thermostat should be set so the
temperature never rises above the flash point of the liquid. Check the MSDS for the
chemical to determine the flashpoint. Compare that flashpoint with the expected
temperature of the reaction to gauge risk of starting a fire.
22.7 Cold Traps
Cold traps:
• Because many chemicals captured in cold traps are hazardous, care should be taken and
appropriate protective equipment should be worn when handling these chemicals.
Hazards include flammability, toxicity, and cryogenic temperatures, which can burn the
skin.
• If liquid nitrogen is used, the chamber should be evacuated before charging the system
with coolant. Since oxygen in air has a higher boiling point than nitrogen, liquid oxygen
can be produced and cause an explosion hazard.
• Boiling and splashing generally occur when charging (cooling) a warm container, so
stand clear and wear appropriate protective equipment. Items should be added slowly
and in small amounts to minimize splash.
• A blue tint to liquid nitrogen indicates contamination with oxygen and represents an
explosion hazard. Contaminated liquid nitrogen should be disposed of appropriately.
• If working under vacuum see the “reduced pressure” section.
• See “cryogenics” for safety advice when working with cryogenic materials.
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