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<p>Infrared (IR) photoacoustic spectroscopy (PAS) using band-pass filters is a widely used method for measurement of <span class="inline-formula">NH₃</span> and greenhouse gas emissions (<span class="inline-formula">CH₄</span>, <span class="inline-formula">N₂O</span> and <span class="inline-formula">CO₂</span>) especially in agriculture, but non-targeted gases such as volatile organic compounds (VOCs) from cattle barns may interfere with target gases, causing inaccurate results. This study made an estimation of <span class="inline-formula">NH₃</span> interference in PAS caused by selected non-targeted VOCs which were simultaneously measured by a PAS and a PTR-MS (proton-transfer-reaction mass spectrometry). Laboratory calibrations were performed for <span class="inline-formula">NH₃</span> measurement, and VOCs were selected based on a headspace test of the feeding material (maize silage). Strong interferences of VOCs were observed on <span class="inline-formula">NH₃</span> and greenhouse emissions measured by PAS. Particularly, ethanol, methanol, 1-butanol, 1-propanol and acetic acid were found to have the highest interferences on <span class="inline-formula">NH₃</span>, giving empirical relationships in the range of 0.7 to 3.3&thinsp;ppmv&thinsp;<span class="inline-formula">NH₃</span> per ppmv&thinsp;VOC. A linear response was typically obtained, except for a nonlinear relation for VOCs on <span class="inline-formula">N₂O</span> concentration. The corrected online <span class="inline-formula">NH₃</span> concentrations measured by PAS in a dairy farm (with empirical relationships <span class="inline-formula">2.1±0.8</span> and <span class="inline-formula">2.9±1.9</span> for Location 1 and Location 2, respectively) were confirmed to be correlated (<span class="inline-formula"><i>R</i>²=0.73</span> and 0.79) to the <span class="inline-formula">NH₃</span> concentration measured simultaneously by the PTR-MS when the empirical corrections obtained from single VOC tests were applied.</p>