Risk assessment is a legal obligation for all companies in most countries worldwide. It aims to control the quality of working conditions and avoid externalizing the consequences of accidents and resulting costs to society. This work discusses the need for an adequate interpretation of the zero-risk concept from a technical-preventive perspective to assess occupational risks in construction sites. A critical analysis of several risk assessment methodologies was carried out, focusing on the evaluation criteria of little or no-risk situations. The verification of the results was made through a case study. The perception of health and safety risks by workers is very different from that of the evaluators. Often, when workers identify a situation as low-risk or even zero-risk, the evaluator assesses the same context as maximum risk. Given the workers’ and the evaluators’ responses, the Preventive Action Method establishes a new parameter, the Environment Congruence. This parameter is based on the perception of the preventive environment and gives more importance to the evaluators’ decision. When preventive action is optimal, the risk is low in all preventive observation settings. In conclusion, this study justifies the non-nullity of the risk and the difficulty of assessing zero-risk in construction sites. Therefore, evaluations with qualitative and quantitative non-risk approaches should be discarded.

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