To detect a gas chlorine leak, what is the best method to use?

When detecting a gas chlorine leak, using a substance that reacts with chlorine is essential for accurate identification. Ammonia is a suitable choice because it forms a visible white cloud or vapor when it comes in contact with chlorine gas. This reaction produces chloramines, which are easily noticeable, indicating the presence of a chlorine leak.

This method is effective as it provides a visual cue, making it easier for contractors and pool service professionals to locate the source of the leak and take necessary action. In contrast, the other substances listed do not have the same reactive properties that would indicate the presence of chlorine gas. For example, vinegar and water are neutral solutions that wouldn't result in a detectable reaction with chlorine, while a plastic bottle containing chlorine would not be a practical means of detection and may pose a safety risk if it were to leak. Thus, using ammonia is the safest and most effective method for identifying a chlorine gas leak in pool environments.