Results. We find no significant changes in the warm absorber on either short timescales (similar to 2 days) or longer ones (two and a half years), as the variations in the ionic column densities of the most relevant elements are below the 90% confidence level. The variations could still be present but are statistically undetected given the signal-to-noise ratio of the data. Starting from reasonable standard assumptions, we estimate the location of the absorbing gas, which is likely to be associated with the putative dusty torus rather than with the broad line region if the outflowing gas is moving at the escape velocity or greater.