Which substance is primarily detected by gas detectors used in LPG and CNG applications?

Gas detectors used in LPG (Liquefied Petroleum Gas) and CNG (Compressed Natural Gas) applications are specifically designed to identify hydrocarbons, primarily propane and methane. These gases are the main constituents of LPG and CNG, respectively, and are lighter than air, which makes them hazardous when they leak in enclosed spaces.

Propane, which is commonly used in heating, cooking, and as engine fuel, is significant for detection because of its flammability and potential for explosion. Methane, the primary component of natural gas, is also crucial to monitor due to similar safety concerns. Both gases are typically odorless, but manufacturers often add odorants to them to ensure leaks can be detected by smell.

The other options listed consist of substances that either do not play a direct role in LPG and CNG applications or are not typically the focus of gas detection efforts. For instance, while butane and ethane may be present in LPG, they are not the primary gases detected. Carbon dioxide and nitrogen are often outputs of combustion processes but are not the primary fuels being monitored. Hydrogen and oxygen are crucial for combustion reactions but are not typically detected in the context of LPG and CNG leak detection.