Case 9

Smoke Management

[Ferriera, M. J. (1998), (2002)]

• Analysis of Smoke Control System Design Using a Computer-based Airflow Analysis Pacific Rim Conference and Second International Conference on Performance-Based Codes and Fire Safety Design Methods, Maui, Hawaii, 1998.
• Use of Multizone Modeling for High-Rise Smoke Control System Design 2002, ASHRAE Annual Meeting, 2002.

This case study involved the analysis of a smoke management system in a large multi-building complex. Fire protection engineers investigated the inter-zonal airflows and pressure differences that would be produced by the activation of zoned smoke control systems and the far-field tenability conditions that might exist under various fire scenarios. One of the buildings in the complex was represented within CONTAM as having over 100 levels, more than 3,000 zones and over 10,000 airflow paths connecting the zones.

CONTAM was not developed with near-field fire modeling in mind, so the users had to develop creative ways to simulate near-field smoke transport. For example, buoyancy-induced flow due to a fire was modeled by creating a contaminant zone around the fire region and implementing fan-flow elements to simulate the ceiling jets caused by smoke plumes impinging on the ceiling. The contaminant within the zone in this case was a generic contaminant called "smoke." Naturally, great care must be taken when implementing the model in this way, but the method established proved to be quite useful to the users.

One objective of the project was to investigate the performance of a zoned smoke control system that was being planned for a part of a renovation project. CONTAM's simple air handling systems were used to model fifteen HVAC/smoke control zones containing supply and return air handling systems, retail and food area supply and exhaust systems, kitchen exhaust systems and smoke control systems. Many different simulations were performed to evaluate the performance of the smoke control systems under varying HVAC and smoke system operating modes for different fire scenarios. This analysis revealed some unexpected interactions between the smoke control systems and the HVAC systems.

Tenability analysis was used to estimate safe refuge distances from smoke spread. Two tenability criteria were established - one for visibility distance and another for carboxyhemoglobin levels. Visibility and carboxyhemoglobin levels were calculated based upon the concentration of smoke and carbon monoxide, respectively, generated from a given mass of fuel burned.