Examples of continuum subtraction on two adjacent, high-flux pixels at the IR source A of IRAS18089 that show contrasting behaviors. The pixel spectrum of the left panel displays the Humphreys alpha line, while the spectrum on the right panel shows a deep artifact that we masked prior to the fitting (red line). In this case the artifact consists of two contiguous, negative channels, where the deeper one is capable of deviating the polynomial fit significantly. The shaded area highlights the spectral range that was excluded when fitting the continuum. The left panel is, at the same time, a good representation of how the continuum subtraction works for the remaining five regions as they do not show negative artifacts. The vertical lines show the nominal wavelength of the Hu α line.