Water vapour falsely increases carbon dioxide and volatile anaesthetic readings, as it absorbs infrared at several wavelengths.

Oxygen broadens the carbon dioxide absorption spectra, resulting in lower readings.

Carbon dioxide and nitrous oxide have similar infrared absorption bands. Carbon dioxide absorbs strongly between wavelengths of 4.2 and 4.4 μm and nitrous oxide absorbs strongly between 4.4 and 4.6 μm. The close proximity of these bands may result in overlap of absorption peaks. Use of a narrow-band filter at 4.3 μm (the wavelength at which carbon dioxide is most strongly absorbed) can overcome this problem.

Nitrous oxide in a gas mixture containing carbon dioxide can produce collision broadening. This occurs when infrared energy absorbed by a carbon dioxide molecule is emitted as a photon if it randomly collides with a nitrous oxide molecule. This enables the carbon dioxide molecule to absorb more infrared light energy, falsely increasing the measured concentration of carbon dioxide. This effect also broadens the absorption spectrum of nitrous oxide (as it is in effect absorbing energy within the spectrum of carbon dioxide). Modern analysers can compensate by measuring the concentrations of interfering agents.

Alcohols can also cause inaccuracies by falsely elevating volatile anaesthetic agent readings.