Hazard alerts (2013)

Visitor and meeting room chairs

Several chairs of the model pictured above have been found to have fractures in the plastic mounting sleeves where the back is attached to the base stems.

What to do:

1. confirm whether you have this model in use
2. check for fractures around the area as shown in the photo
3. remove any damaged chairs from use immediately.

DEWAR flasks for cryogenic liquids

Dewar flasks are commonly used to store liquid nitrogen in small amounts. They may act as cold traps attached to scientific equipment. These Dewars are either glass, stainless steel or high-density polyethylene (HDPE).

A recent incident occurred with a glass Dewar flask. Several minutes after filling the Dewar with liquid nitrogen the Dewar imploded without warning. Fine glass spread in 1 to 2 m radius and liquid nitrogen leaked.

Dewar flasks are subjected to significant changes in temperature when being repeatedly filled. These stresses can result in the glass cracking and the vacuum failing. There is generally no visible sign if a Dewar has micro cracks, or methods for testing or predicting when it will fail. In addition, the glass supporting seals may allow liquid nitrogen in between the container walls. As the liquid converts to gas the pressure may cause the glass or container to fail.

Please inspect your work area for glass DEWARS. Consider the risks if your glass Dewar flask fails, and the consequence to people and your equipment. If you have any glass Dewars please consider replacing them with stainless steel or high-density polyethylene (HDPE) versions or replacing them after several years of service. Inspect any supporting seals regularly for cracks or perishing.

Domestic glass thermoses are not suitable for cryogenic liquids. Use only laboratory grade Dewar flasks.

For further information contact the OHS Branch (OHS.Officer@anu.edu.au, x52193).