Objective: We investigated behavior and attitudes of smoking workers employed by Showa University Karasuyama Hospital before and after smoke-free actions were undertaken in their workplace. We simultaneously examined whether understanding their own expired carbon monoxide (COex) values led them to quit smoking.

Subjects and Methods: Subjects were 33 workers who used the smoking area in their workplace before starting the smoke-free action. Questionnaires about their smoking habits were completed and COex concentrations were measured just prior to starting the smoke-free action and one, three and six months after this had commenced.

Results: Out of the 32 workers who were followed for 6 months, 19 subjects including three quitters reduced smoking. “Smoke-free action within their workplace” was answered as the main reason of moderating or quitting smoking by 16 subjects, and “grasping their COex value” by two subjects. COex values significantly correlated both with the number of cigarettes per day and with the interval time since smoking.

Discussion and Conclusion: Smoke-free action within a workplace has clearly helped smokers moderate smoking. It is suggested that, for the smokers who associated COex value with smoking amount, understanding their own COex values can lead them to moderate smoking, without individual instruction about smoking cessation.