Sir,Gas masks were first used during World War I to protect soldiers against poisonous gases. They have been particularly used in recent years in the aftermath of industrial accidents, fires and natural disasters. The importance of gas masks has come to the forefront in view of the possibility of accidents/terrorist attacks. The use of respiratory protective equipment is often favored in a rescue setting because it is generally a very effective and cheaper option. The use of gas masks can, therefore, be very useful in saving human lives. The combination of carbon oxide and hydrogen cyanide with blood hemoglobin causes heavy poisoning, which is often lethal. It has been found that hemoglobin and plasma proteins have a vast buffer capacity.[1] They combine with acids and bases, including gases with acid and alkaline characteristics.[2] It has been proved that lyophilized blood products are highly hygroscopic and can absorb gases and evaporations of toxic chemical substances. Contemporary sorbents for filtrating gas masks are based on active carbon. Abilities for sorption for some gases depend considerably on the presence of trace metals like copper, silver and cobalt.A study performed by our group used sheep blood provided by the Institute of Communicable and Parasitic Diseases (Sofia), which was prepared as erythrocyte mass, and plasma Alsever's solution modified by Bukantz was required. Samples were freeze-dried and analyzed by electron paramagnetic resonance (EPR).EPR is useful for characterizing both transition metal ions and free radicals in blood.[3] The EPR spectrum of freeze-dried erythrocytes consisted of two signals with g-factors of 4.3 and 2.0, respectively. Both signals display different line widths: the signal with g = 4.3 is broader than the signal with g = 2.0. The signal with g = 4.3 is typical for Fe3+ ions in a crystal field with rhombic symmetry[45] while the signal with g = 2.0 can be assigned to Fe3+ in octahedral crystal field. Contrary to freeze-dried erythrocytes, freeze-dried blood plasma was EPR silent.The study indicated that the iron present in freeze-dried erythrocytes possibly plays a role in absorption of toxic gases. EPR can play a role in the evaluation of material for gas masks. The gas masks based on blood products may be useful in the management of industrial chemical disasters, particularly those involving the release of hydrogen disulfide, sulfur dioxide, carbon monoxide and mercaptans. Gas masks based on lyophilized blood products can help save human lives in case of industrial chemical disasters.