What type of system incorporates specific nozzles and methods of application differing from standard listings and testing laboratory specifications?

The type of system that incorporates specific nozzles and methods of application differing from standard listings and testing laboratory specifications is the pre-engineered system. Pre-engineered systems are designed and manufactured to meet specific needs or conditions of a facility, providing flexibility in their components and methods. This adaptability allows them to function effectively in a range of scenarios, accommodating unique design requirements and installation challenges.

In a pre-engineered system, the nozzles and application methods are selected intentionally based on the system's requirements rather than strictly adhering to general industry standards. This allows for innovation and customization to optimize performance based on the specific environment or hazards present.

Custom-built systems could also suggest some level of deviation from standard practices, but they refer more generally to entirely tailored systems created for specific applications rather than a structured approach that employs pre-defined engineered components. Standard systems adhere to established specifications and protocols set by testing laboratories, while open-source systems typically focus on freely available designs and methods rather than specialized hardware or application techniques. Thus, the correct choice reflects the nature of flexibility and specificity inherent in pre-engineered systems.