You've identified a valid concern regarding smoke detection in the conference/assembly room with the Nanawall configuration. Here's a breakdown of the issues and potential solutions, considering the code implications

Understanding the Challenges
Dilution and Airflow

The primary issue is the potential for outdoor airflow to dilute smoke concentrations below the detection threshold of the plenum return air smoke detectors, or draw it away entirely through the open Nanawalls. This defeats the purpose of early detection and notification.

VAV Closure

While the VAV boxes closing might prevent supply air circulation, the open return air plenum transfer ducts still provide a pathway for air (and potentially diluted smoke) to reach the central return. However, the dilution factor may be too high for effective detection at that point.

Code Considerations

While the building is sprinklered, relying solely on sprinkler activation is not ideal for life safety. Fire alarm systems are intended to provide early notification to allow for evacuation before sprinkler activation. The code requires smoke detection for initiating the voice evacuation and, depending on the jurisdiction and occupancy load, additional life safety functions.

Potential Solutions

Here's a range of options, from simple to more complex, and what to consider when choosing one:1. Area Smoke Detectors

This is the most reliable and common solution. Install spot-type smoke detectors within the conference/assembly room itself, in addition to the return air smoke detectors.

Placement

Locate detectors per NFPA 72 guidance, considering ceiling height, room geometry, and potential obstructions. A professional fire alarm system designer can determine the optimal number and placement. Consider areas where smoke is more likely to accumulate.

Code Compliance

This is the most direct way to meet the intent of the code. It provides localized smoke detection regardless of the Nanawall position.

Accordion Wall

Make sure detector placement considers the room configurations when the accordion wall is open or closed. It may be a design requirement to add more detectors to ensure coverage of both configurations.2.

Addressable Smoke Detectors with Sensitivity Adjustment

If you choose the option of area detectors, consider using addressable smoke detectors. These detectors will allow sensitivity adjustments based on different room usage.

Code Compliance

UL 268 7th edition requires that smoke detectors be tested to detect fast, slow and smoldering fires. It may be necessary to program the detector for "high" sensitivity.

Minimize False Alarms

Consider using "multi-criteria" detectors, which combine smoke and heat sensors. This reduces false alarms caused by cooking activities or steam, while still providing reliable fire detection.3.

Nanawall Position Monitoring and System Adjustment

This is a more complex and potentially expensive solution:

Sensors

Install sensors on the Nanawall panels to detect when they are open.

Control System

Integrate these sensors with the fire alarm control panel (FACP) or a building automation system (BAS) that can communicate with the FACP.

Programming

Program the system to: Increase the sensitivity of the return air smoke detectors when the Nanawalls are open. Activate additional audible/visual notification appliances within the conference/assembly room when the Nanawalls are open, ensuring occupants are alerted even if the smoke is diluted. Potentially change the HVAC system operation (e.g., increase exhaust fan speed to remove smoke).

Challenges

This approach requires significant integration and programming. The reliability of the sensors and control system is critical. Code compliance might be a harder sell to the AHJ (Authority Having Jurisdiction) without supplemental area smoke detectors.

Advantages

It can theoretically optimize the system's performance based on real-time conditions.4.

Computational Fluid Dynamics (CFD) Analysis

This is the most sophisticated (and expensive) option.

Modeling

Create a detailed CFD model of the conference/assembly room, including airflow patterns, heat transfer, and smoke propagation under various Nanawall configurations and wind conditions.

Detector Placement

Use the CFD results to optimize the placement of return air smoke detectors or area smoke detectors to ensure reliable detection under all scenarios.

Code Justification

The CFD analysis can provide strong justification for the proposed smoke detection strategy to the AHJ.

Challenges

Requires specialized expertise and software. The accuracy of the results depends on the quality of the model and the input data.

Recommendations Start with Area Smoke Detectors

This is the most straightforward, cost-effective, and universally accepted solution. Focus on proper placement according to NFPA 72.

Consult with a Qualified Fire Protection Engineer or Fire Alarm System Designer

They can assess the specific conditions of your project, perform calculations, and provide recommendations that meet code requirements and ensure effective fire protection.

Engage the AHJ Early

Discuss your proposed smoke detection strategy with the local building official or fire marshal to ensure their acceptance. Be prepared to provide supporting documentation, such as detector specifications, placement diagrams, and potentially CFD analysis if needed.

Document your design decisions

Detail your reasoning, the codes and standards you followed, and any assumptions you made. This documentation will be valuable for plan review, inspections, and future maintenance.

Key Considerations



NFPA 72 (National Fire Alarm and Signaling Code)

This is the primary standard governing the design, installation, and maintenance of fire alarm systems.

Local Building Codes

These codes may have specific requirements for smoke detection based on occupancy type and building features.*

Authority Having Jurisdiction (AHJ): The local building official or fire marshal has the final say on whether your fire alarm system design is acceptable.In conclusion, while your sprinkler system provides a crucial layer of protection, relying solely on it is insufficient for life safety in a large assembly space. Area smoke detection, combined with professional design and AHJ approval, is the most reliable way to address the challenges posed by the Nanawalls and ensure effective fire alarm system performance. Flag for review