Safety When Using Cryogenic Substances

Cryogenic substances  are used  in research to maintain ultra-cold temperatures.  Liquid nitrogen is hazardous because it can maintain temperatures as low as degrees -153°C (-243 °F).  In addition, liquid nitrogen releases vapors that can deplete the available oxygen in the area.  Dry ice, which is solid carbon dioxide also presents a hazard.  Dry ice begins to sublime at temperatures above -78°C ( -109°F). This means the solid carbon dioxide is converted directly to carbon dioxide vapor and can create an oxygen deficient atmosphere.

The low temperatures of dry ice and liquid nitrogen can burn skin upon contact and prolonged skin exposure can freeze bare skin causing frost bite.  For these reasons, dry ice and liquid nitrogen require special handling to protect the skin, face, and eyes.  Additionally, the areas where lab workers handle these substances must have adequate ventilation.  Adequate ventilation means providing ventilation that can limit the accumulation of nitrogen or carbon dioxide vapors.

The following list provides examples of safe work practices:

* Avoid eye, face, and skin contact with liquid nitrogen or dry ice.  Always wear safety glasses, lab coat, and close-toed shoes.

* Never handle dry ice or liquid nitrogen with bare hands.  When retrieving samples or vials from freezers, wear cryogenic gloves to protect the skin on your hands, wrists, and forearms.  For additional protection from liquid nitrogen, purchase water proof cryogenic gloves

* Do not use or store dry ice or liquid nitrogen in confined areas.  Proper ventilation is required to prevent oxygen from being depleted from the atmosphere.

* Never store a cryogen in a sealed, airtight container.  The pressure from vapors can cause an explosion.

* When filling containers with liquid nitrogen (e.g. dewar flasks, carboys) be sure the transfer line is stable and secure.  If the transfer line is not secured during filling, liquid nitrogen can be spray out of the container.  This can present a skin contact hazard.

* If you need to ship samples using liquid nitrogen or dry ice, you must have completed Shipping Training in the past two years.


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