Figure 1. The total number of new cases examined each month (solid line), the number of patients oto-neurologically positive (dashed line). The vertical line denotes the end of petrol (gasoline) restriction. The study includes 700 patients exposed to gases; 263 with chronic CO poisoning based on symptoms; 401 exposed to CO in their workplaces but whose symptoms could not established with certainty; 36 exposed to other gases (SO₂, H₂S, etc.)