Atmospheric pressure and temperature excursions at constant volume for oxidation of high temperature sodium are investigated analytically. Data under both the adiabatic condition and the time dependent transient heat transfer condition are reported. The analyses represent parametric cases involving variations in containment geometry, variations in sodium conditions, and variations in contained gas conditions including oxygen concentrations of 0 to 21 vol%. The objective is to obtain data for design of containment for the Fast Flux Test Facility. Design of containment requires a knowledge of maximum temperatures and pressures to be expected as a consequence of the unlikely occurrence of a high volume sodium leak. This information is presented in graphical and tabular form.