The aim of this work is to study the influence of initial pressure on the limiting oxygen concentration for a biomass dust. Atmospheric tests were carried out in the 20-1 sphere. Hyperbaric tests at 0.5, 1.2 and 1.8 MPa were developed in a 1-m3 spherical vessel. This study used unusually high initial testing pressures, and it was performed with a renewable material with great potential in pressurized processes that has very special properties such as its low density and fibrousness. Contrary to the trend indicated by other research (usually for coal), it has been found for biomass that an increase of the initial pressure yields an increase in the limiting oxygen concentration.