Answer:
1. It may become toxic at an elevated partial pressure, which may be the result of a rise in inspired oxygen concentration, an increase in environmental pressure or a combination of both.
2. Chlorine is a very reactive element, causing it to quickly form compounds with other substances. Chlorine also has the ability to develop a bond between two substances that do not normally react with one another.
3. The fact that some metal ions kill or inhibit the growth of microorganisms.
4. A substance that vaporizes readily.
