Which two units are commonly used in international fire protection?

The use of liters and bars as units in international fire protection is rooted in the metric system, which offers a standardized approach that is widely adopted around the globe. Liters are utilized to measure volumes of water required for fire suppression efforts, such as in the sizing of piping systems and determining water supply for sprinkler systems. The bar, a metric unit of pressure, is often used in calculations related to fire protection systems, especially in relation to water supply pressures, pump specifications, and other fluid dynamics relevant to sprinkler systems.

In contrast, gallons and PSI (pounds per square inch) are primarily used in the United States; thus, they are less relevant in an international context. Similarly, pounds and Celsius, while they do measure weight and temperature respectively, are not typically standard measurements in fire protection systems across different countries. Lastly, ounces and inches are imperial units that are not aligned with the metric system, which is preferred by most countries for scientific and engineering purposes. Therefore, the use of liters and bars aligns with the global standards in fire protection, making them the correct choice.