Ventilation to Eliminate Oxygen Deficiency in a Confined Space Part I: A Cubical Model

Abstract

Abstract Oxygen deficiency is a significant potential hazard for work in confined spaces and can be eliminated by providing adequate mechanical ventilation. This study investigated ventilation effectiveness for restoring depleted oxygen levels in a confined space model. Design parameters included space configuration (cubical shape, open-top vs. closed-top); ventilation mode (exhaust vs. supply), volume flow rate, and inlet/outlet elevation; and location inside the space. Preliminary studies indicated that oxygen recovery for the open-top case was very rapid, even without mechanical ventilation, and this case was not studied in further detail. Oxygen recovery in the closed-top case was generally more rapid for supply ventilation than for exhaust. Ventilation effectiveness (oxygen recovery) improved with increasing flow rate, to a cut-off point above which little additional improvement was shown. Ventilation effectiveness was also affected by inlet/outlet elevation and location in the space. Oxygen recovery occurred in an exponential manner as a function of time, which provided a basis for regression of the experimental data. Regression coefficients established a data base which may be useful in the development of computer modeling for ventilation design. This study is a first step in a more comprehensive program to evaluate and understand ventilation for confined spaces. Limitations constitute opportunities for further study, e.g., modeling size variations, noncubical model shapes, and variable contaminant characteristics. Garrison, R.P.; Nabar, R.; Erig, M.: Ventilation to Eliminate Oxygen Deficiency in a Confined Space. Part I: A Cubical Model. Appl. Ind. Hyg. 4:1–11; 1989.