Which factor affects the placement of smoke detectors regarding air velocity?

The placement of smoke detectors is influenced by air velocity because high air velocity can disrupt the ability of smoke to reach the detector. When air is moving at a significant speed, it can dilute or carry smoke away from the detector, potentially delaying or preventing activation. Therefore, it is recommended that the air velocity in the vicinity of smoke detectors should be maintained at less than 1.5 meters per second. This standard ensures that the detector can effectively sense smoke particles without interference from rapidly moving air. Keeping the air velocity below this threshold helps to optimize the performance and reliability of smoke detection systems, making it crucial for safety in various environments.

The other options suggest higher air velocity limits or lack of requirements, which would not ensure effective smoke detection, potentially compromising safety. Hence, understanding air velocity limits is essential for proper smoke detector placement and functionality.