The interaction of oxygen gas with the (110) face of tungsten single crystal has been investigated by the techniques of electron stimulated desorption combined with surface mass spectrometry. At 300K two states with desorption efficiencies of 6*10^-7 and 5*10^-6 ion/electron for production of O⁺ ions are observed in the adsorption scheme. The former state forms rapidly on introducing gas to the clean surface and is essentially complete at an exposure of 0.3*10^-6L. The two states are identified with different temperature regimes of around 350 and 750K for the removal of ion current and with total desorption cross sections of respectively 2*10^-17 and 5*10^-19 cm². Measurements of the energy distribution of desorbed ions reveal a difference of around 1.2 eV between the values of most probable ion energy from the two states.