In a recent meeting about risk with folks at Underwriters Laboratories (UL), we were discussing examples that highlight the difference between hazard, hazardous situation, and harm. Here are two such examples.
Consider a room with two kids and an adjacent kitchen with a knife in it. This setup is hazard free (under the assumption that the kids cannot enter the kitchen). Now, suppose the knife is brought into the room and placed on the floor. In this setup, the knife presents a hazard (danger). If one of the kid picks up the knife, then we are presented with a hazardous (dangerous) situation. If the kid now hurts itself or the other kid, then we have harm.
Note that the knife by itself is not a hazard. The possibility of the knife being picked up by the kid makes the knife a hazard. The act of the kid picking up the knife leads to a hazardous situation. The use of the knife in harmful ways leads to harm. In all of this, we assume a kid holding a knife is likely to cause harm.
As another example, consider a kitchen with a gas stove. The gas in the stove does not present a hazard. Suppose the gas leaks into the kitchen and is trapped in the kitchen. Now the gas presents a hazard. If a human enters the kitchen, then we have a hazardous situation. Any ignition can then lead to harm. Here we assumed harm as damage to only humans (not to property).
In the above scenario, suppose the gas was not trapped in the kitchen (due to an open window) to eventually cause harm. Since the possibility of harm is eliminated, the gas does not present a hazard.
Similarly, suppose we define harm as damage to property and humans. Now, even without a human entering the kitchen, the gas trapped in the kitchen can lead to harm. Hence, the gas presents a hazard.