Conclusion
Halitosis, also known as bad breath, can be caused by various factors, some of which originate in the mouth, while others may stem from elsewhere in the body. Here are some of the most common reasons and causes of bad breath or halitosis:

Smoking is a bad habit any way you slice it, but one thing it’s fairly well known for is causing halitosis, or “smoker’s breath.” Smoke particles can linger in the throat and lungs for hours, giving your breath a stale scent. The chemicals in tobacco smoke also remain in the mouth, leading to a whole host of secondary causes of bad breath. As mentioned briefly above, tobacco can lead to chronic bad breath by drying out the tongue and gums, leaving a chemical-filmed environment where oral bacteria can run amok. Giving up smoking is good for your body in many ways. Forget better breath – you’ll have a better quality of life!
Many smokers suffer from bad breath from time-to-time. Heavy smokers are usually more frequently affected, but occasional smokers also get bad breath. Studies suggest that smokers experience a deterioration in sensitivity, so you may not even realize you have bad breath or be able to smell it on yourself.