Which of the following is a consequence of a gas leak?

A gas leak poses significant health risks and can lead to potential explosions due to the flammable nature of gases like natural gas and propane. When gas escapes into an area, it can accumulate and create an explosive atmosphere, especially if there is an ignition source nearby. Additionally, inhaling gas can result in various health issues, including respiratory problems, headaches, dizziness, and even more severe effects in high concentrations.

In contrast, increased appliance efficiency, reduced need for combustion air, and improved air quality are not direct consequences of a gas leak. A gas leak typically indicates a malfunctioning or improperly maintained appliance, which usually leads to decreased efficiency rather than an increase. Moreover, a gas leak would likely increase the need for combustion air to avoid generating carbon monoxide or other harmful byproducts. Air quality would also deteriorate in the presence of a gas leak due to the release of harmful gases into the environment.