Which type of sprinkler is mounted above the lower plane of the ceiling?

The correct choice is flush sprinkler. A flush sprinkler is specifically designed to be mounted above the lower plane of the ceiling without any visible casing or cover protruding from the ceiling surface. This type of sprinkler blends into the ceiling, providing a more aesthetically pleasing appearance while still being effective in fire protection.

In the context of fire protection systems, it is crucial for sprinklers to be positioned correctly to ensure optimal performance. Flush sprinklers are installed in such a way that they maintain a tidy appearance, which is often desired in commercial and residential spaces where aesthetics matter. They are intended to provide reliable fire suppression while remaining discreet.

Understanding the function and application of flush sprinklers can greatly enhance the design and implementation of fire suppression systems. Therefore, recognizing their installation characteristics is essential for any professional in the field.