禁止吸烟的英语作文可以这样写：

No Smoking

At present, many teenagers smoke. I don't think it's a good phenomenon. It must be stopped, for smoking is harmful in many ways.

Firstly, smoking is bad for our health. As we start smoking, our lungs begin to suffer from the harmful chemicals in tobacco smoke. This can lead to serious diseases such as lung cancer and chronic obstructive pulmonary disease （COPD）. Moreover, smoking can also affect our skin and teeth, making us look older and less attractive.

Secondly, smoking poses a threat to others. When we smoke in public places, it not only harms our own health but also poses a secondhand smoke hazard to others. This can be particularly dangerous for children, the elderly, and people with respiratory problems.

Lastly, smoking is a waste of money. The cost of tobacco products is high, and smoking can lead to addiction, which can strain our financial resources.

In conclusion, smoking is a harmful and addictive habit that must be stopped. We should take action to discourage smoking among teenagers and promote a smoke-free environment. This will not only protect our own health but also contribute to a healthier society.