Which of the following is not a requirement for the installation of flame detectors?

The correct choice notes that all options provided are requirements for the installation of flame detectors, which is inaccurate when considering the context of flame detector functionality.

In flame detection systems, the actual size of the fire that the detector will respond to is indeed a consideration, as it helps determine the effectiveness and operational range of the detector. Some flame detectors are designed for specific sizes and types of fires, ensuring that they can respond before a fire escalates.

The sensitivity of the detector is crucial because it affects how quickly and reliably the detector can sense the radiation emitted by flames. Different environments may require detectors with varying sensitivity levels based on expected fire types and sizes.

However, the absorption of radiant energy from the surrounding atmosphere is not a direct requirement for installation. While environmental conditions can affect detector performance—such as dust, smoke, or humidity, which may obscure the detection of flame—the installation itself does not rely on the absorption characteristics of the atmosphere as a requirement.

Thus, identifying that not all specified conditions are essential for installation clarifies how flame detectors must be evaluated and deployed effectively in various scenarios.