The first Czechoslovak protective mask 23 model, based on the French gas mask ARS, was absolutely insufficient in the 1930’s. Attempts for the construction of a modern protective mask did not meet the requirements of the army and so the problem was solved by the purchase of protective mask by Leyland company (British military mask Mk IV). This mask became a model for the new Czechoslovak protective mask 35 model, which had the same characteristic features, such as its shape or covering of rubber farepiece and wrapped hose to filter with jersey. On the other hand, the difference was in the existence of a bolting on valve chamber that enabled a direct connection of filter to the mask.