To provide a filter capable of forming a respiration environment of comfortable "healing" in addition to a simple function in a system for feeding aqualung respiration gas and medical respiration gas.

In the system for feeding respiration gas, the filter constituted so as to form the environment of "healing" is disposed on a regulator or/and a valve body. A titanium screen having a coated film of non-stoichiometric compound titanium oxide which is formed by allowing metal titanium fine particles to collide with the titanium screen on impact at high speed in an inactive environment is used for a major component of the filter.