A method for attenuating deflagration pressure produced by combustion of combustible gas in a defined region of a process vessel. The method generally comprises selecting and placing attenuating material in the defined region of the process vessel, wherein the selected attenuating material maintains its physical shape under the operating conditions. The attenuating material should occupy at least 20% of the volume of the defined region of the process vessel. Use of the inventive method may be beneficially applied for the safe operation of oxidation reactors with flammable, high hydrocarbon concentration feeds in order to attain increased productivity. The invention also provides a tubular reactor adapted for attenuation of deflagration pressure resulting from combustion of combustible gas in a defined region therein, wherein the defined region of the tubular reactor comprises attenuating material selected in accordance with the aforesaid method for attenuating deflagration pressure and which have a plurality of components which are placed such that void spaces and open pathways between the components are minimized. A method for performing gas phase reactions safely under flammable operating conditions is also provided, wherein a gas feed composition comprising a hydrocarbon and oxygen is subjected reaction in a reaction vessel having attenuating materials therein and the reaction is conducted at a temperature and a pressure which render the reaction system flammable. By using the inventive apparatus, full pressure containment may be achieved, thereby eliminating the need for emergency pressure relief devices.