The real-time analysis of oxygen concentrations in an enclosed space during the evaporation of a liquid nitrogen

Abstract

There are several potential hazards associated with the use of cryogenic liquids, including explosions due to sudden increases in volume upon evaporation, asphyxiation from decreases in local oxygen concentrations and tissue damage resulting from skin contact.

In particular, the leakage of liquid nitrogen in an enclosed space can cause a rapid drop in oxygen concentration and can possibly lead to asphyxiation. The present study used a specially-designed sealed booth to monitor the oxygen concentration at a number of locations following a liquid nitrogen spill at floor level or the introduction of liquid nitrogen from a feed line inside the booth. The oxygen concentration following these incidents was found to vary with the amount of nitrogen spilled and the height above the floor of the feed line. In additional trials involving the introduction of nitrogen gas using a pipe line inserted into the booth, the oxygen concentration was uniform regardless of the height from the floor. The distribution of oxygen concentrations as liquid nitrogen evaporated in the booth was attributed to the high density of the resulting low temperature nitrogen gas. These results show the difference between liquid nitrogen and nitrogen gas leaks and provide helpful safety guidelines.