In the frame of the D-NOSES project, in order to reach the goal of increasing awareness towards the problem of odour pollution on a global level, it is extremely important to define the scientific framework of odorous emissions, by answering fundamental questions about its nature. In this context, one fundamental question is related to the chemical compounds in odour emissions, and their potential to cause health effects. This document provides an overview of the chemical compounds in the odour emissions from different plants, with the purpose of identifying the most ���critical��� compounds from the point of view of their potential toxicity, and provide a list of those compounds, which should effectively be investigated more carefully during monitoring activities. The study was focused on those odour-emitting activities, which also typically cause worries related to potential health effects, i.e. foundries, landfills and refineries. This work involved extensive bibliographic research of the studies that have chemically characterized emissions from the above-mentioned plants. For each of the activities analysed, the chemical compounds associated with their main odour emissions have been listed, together with their Threshold Limit Values (TLVs) and Odour Thresholds (OTs). From these lists, the most ���critical��� compounds from the point of view of their potential toxicological effects on workers have been extracted based on their Hazard Quotients (HQ), i.e. the ratio between the measured concentration and the TLV, with the aim of providing a limited list of the most relevant compounds for each activity, which would need to be most carefully analysed when performing monitoring and analysing of gaseous emissions of these type of industrial plants.