This study is for adults with COPD (Chronic Obstructive Pulmonary Disease) and chronic bronchitis who smoke cigarettes. It examines the benefits of switching from traditional cigarettes (CIG) to a different system called THS (Tobacco Heating System). The goal is to see if people feel better and can breathe easier. Participants are randomly assigned to either keep smoking CIG or switch to THS. The study measures symptoms like cough and shortness of breath, as well as lung function and walking ability. **Key points to consider:** - **Study Duration and Visits:** Participants will be monitored over time with multiple visits to track changes in symptoms and lung function. - **Eligibility:** Participants must be at least 40 years old, have a long history of smoking, and be diagnosed with COPD and chronic bronchitis. - **Risks and Requirements:** Participants need to agree to not quit smoking during the study and must not have used other nicotine products recently. This study does not involve quitting smoking but rather switching methods, which may improve certain health aspects. Participants should be comfortable with frequent visits and monitoring.