A process for pretreatment of a lignocellulosic biomass for converting lignocellulosics to ethanol, which conversion process requires feed preparation, pretreatment, enzymatic hydrolysis, fermentation and distillation, the process for pretreatment comprising the steps of: exposing the lignocellulosic biomass to steam in an exposing step in a treatment vessel at a temperature of 190 to 220 degrees C and an exposure time of 5 to 15 minutes, and purging liquid and volatile inhibitory compounds, which are inhibitory to the downstream hydrolysis and fermentation steps and are generated during the pretreatment process, from the treatment vessel, the removal of the volatile inhibitory compounds is carried out after having reached a pressure of 50 to 200 psig and for a duration of 20 to 600 seconds and the removal of liquid inhibitory compounds purging is carried out after a delay of 10 to 300 seconds following pressurization of the treatment chamber and for a duration of 20 to 600 seconds, wherein the treatment vessel has a volatiles purge device including a valve that is selectively openable to permit flow at a controlled rate for a controlled duration of time, the volatiles purge device is located on the treatment vessel at a vertical position on the vessel above a level of the lignocellulosic biomass and the liquid inhibitory compounds within the vessel, and the volatile inhibitory compounds are removed through the volatiles purge device, and the treatment vessel having a liquid purge device including a valve that is selectively openable to permit flow at a controlled rate for a controlled duration of time, the liquid purge device being located on the treatment vessel at a vertical position which permits removal of the liquid inhibitory compounds in the treatment vessel, and the liquid inhibitory compounds are removed through the liquid purge device. exposing the lignocellulosic biomass to steam in an exposing step in a treatment vessel at a temperature of 190 to 220 degrees C and an exposure time of 5 to 15 minutes, and purging liquid and volatile inhibitory compounds, which are inhibitory to the downstream hydrolysis and fermentation steps and are generated during the pretreatment process, from the treatment vessel, the removal of the volatile inhibitory compounds is carried out after having reached a pressure of 50 to 200 psig and for a duration of 20 to 600 seconds and the removal of liquid inhibitory compounds purging is carried out after a delay of 10 to 300 seconds following pressurization of the treatment chamber and for a duration of 20 to 600 seconds, wherein the treatment vessel has a volatiles purge device including a valve that is selectively openable to permit flow at a controlled rate for a controlled duration of time, the volatiles purge device is located on the treatment vessel at a vertical position on the vessel above a level of the lignocellulosic biomass and the liquid inhibitory compounds within the vessel, and the volatile inhibitory compounds are removed through the volatiles purge device, and the treatment vessel having a liquid purge device including a valve that is selectively openable to permit flow at a controlled rate for a controlled duration of time, the liquid purge device being located on the treatment vessel at a vertical position which permits removal of the liquid inhibitory compounds in the treatment vessel, and the liquid inhibitory compounds are removed through the liquid purge device.