Batteries, in particular lithium-ion (Li-ion) batteries, are seen as an alternative to fossil fuels in the automotive sector. Li-ion batteries, however, have some safety issues including possible emissions of toxic fluorine-containing compounds during fire and other abuse situations. This paper demonstrates the possibilities to use the Fourier transform infrared technique to assess some of the most important compounds, including hydrogen fluoride and the far less often measured POF3 and PF5. The study is conducted in the cone calorimeter with different solvents used in Li-ion batteries. The measurements show that, in addition to hydrogen fluoride, with a known high toxicity, POF3 is emitted and can be quantified using Fourier transform infrared.