Final answer:
A positive drain system ensures that the contents of the water, gas, and steam pipelines flow out of the building, preventing accidents or contamination.
Step-by-step explanation:
A positive drain system ensures that the contents of the water, gas, and steam pipelines flow out of the building. This system is commonly used in industries or facilities where the fluids being transported are hazardous, such as nuclear power plants or laboratories. By having the contents flow out of the building, it helps to prevent any potential accidents or contamination from occurring inside the building.