Booking an electric rice cooker to cook porridge may seem convenient, but it can pose several risks and hazards. Here are some of the potential dangers associated with this practice:

1. **Fire Hazard**: Leaving an electric rice cooker unattended for an extended period of time while cooking porridge can increase the risk of a fire breaking out. If the porridge boils over or if there is a malfunction in the cooker, it could lead to a fire in the kitchen.

2. **Overheating**: Cooking porridge in a rice cooker for too long can cause the appliance to overheat. This can not only damage the cooker but also pose a risk of starting a fire or causing burns if touched accidentally.

3. **Food Safety**: Porridge requires a longer cooking time compared to rice, and booking a rice cooker for this purpose may not be ideal for maintaining food safety standards. The prolonged cooking time can lead to bacterial growth in the porridge, especially if it is left sitting in the cooker for an extended period after cooking.

4. **Electrical Safety**: Booking an electric appliance like a rice cooker for a task it is not specifically designed for can put a strain on the electrical system. This can increase the risk of short circuits, electrical shocks, or other electrical hazards.

5. **Warranty Concerns**: Using an electric rice cooker for purposes other than cooking rice may void the warranty of the appliance. If any damage occurs while cooking porridge in the rice cooker, it may not be covered under the warranty, leading to additional costs for repair or replacement.

6. **Inefficient Cooking**: Electric rice cookers are designed to cook rice efficiently and evenly. Using them to cook porridge may not result in the desired texture or consistency, as the cooking settings are optimized for rice rather than porridge.

In conclusion, while it may seem convenient to book an electric rice cooker to cook porridge, it is important to consider the potential risks and hazards involved. It is advisable to use appliances for their intended purposes to ensure safety, efficiency, and longevity.