What type of temperature rating is required for heat detectors installed in elevator hoistways prior to sprinkler activation?

Heat detectors installed in elevator hoistways prior to sprinkler activation are typically required to have a lower temperature rating. The reason for this is that elevator hoistways can be subject to significant temperature variations, especially during fire conditions. Lower temperature-rated heat detectors are designed to activate at lower temperatures, which is critical for early warning in these environments.

These detectors must respond promptly to heat from a fire before sprinkler activation occurs, allowing for evacuation and additional safety measures to be implemented. If the detectors were rated for higher temperatures, they might not activate in time to provide the necessary protection in these critical areas.

The other options like standard, adjustable, or higher temperature ratings would not provide the timely response needed in a potentially hazardous environment where fires can escalate quickly. Thus, a lower temperature rating ensures that the heat detectors can function effectively in early detection scenarios in elevator hoistways.