Managing Smoke In A Health Care Facility
The special nature of the occupants and activities in these facilities create special IAQ requirements, and the concerns only multiply when fire and smoke enter the picture.
LIMITING THE QUANTITY OF SMOKE PRODUCED
CONTAINING SMOKE TO THE ROOM OF ORIGIN
BEYOND THE ROOM OF ORIGIN
- Maximum smoke compartment. Most codes limit the area of a smoke compartment to 22,500 sq ft, which has an effect of limiting the number of occupants that may be exposed to a fire within a smoke compartment. Recent code change activity in both the NFPA and ICC processes has proposed to increase the area to 40,000 sq ft.(viii)
- Minimum size of the area of refuge. While not establishing a minimum area of a smoke compartment, NFPA 101 requires a mini-mum area to be provided in adjacent smoke compartments to accommodate the occupants that may be relocated to the smoke compartments should people need to be relocated to an adjacent smoke compartment. The minimum area is a function of the occupancy classification of the area served.
- Travel distance to the smoke barrier door. In an attempt to address the time required to relocate occupants to an adjacent smoke compartment, NFPA 101 restricts the travel distance to a door of the smoke barrier. The travel distance to the smoke barrier door is restricted, even if an exit is located closer than the smoke barrier door.
- The smoke barrier is continuous from floor slab to the roof deck or floor slab above with all penetrations properly protected. While not required by NFPA 101, the IBC contains requirements for a leakage rating for through penetration firestop systems used in smoke barriers.
ENGINEERED SMOKE CONTROL SYSTEMS
OTHER SMOKE CONTROL FEATURES
- The corridor of a health care facility may not be used as part of the supply or return for the building HVAC system.
- Smoke detection is required downstream of the supply fan and filter to initiate system shutdown should the smoke detector detect smoke in the duct.
- Smoke detection and controls are required to prevent the recirculation of smoke from the return system.
Smoke Control in High-Rise Buildings
- Atrium smoke control systems — These systems are required for open atriums and consist of a mechanical smoke exhaust system to extract smoke from the top of the open atrium while providing low-level, low-velocity make-up air at the bottom of the atrium in order to maintain the smoke layer above the occupied areas and their associated means of egress for a specified time period.
- Smokeproof stair enclosures — Most building codes require high rise buildings to be provided with smokeproof exits stairs. The International Building Code (IBC) allows three methods for compliance: exterior stair balconies; mechanically ventilated stair vestibules; or stair pressurization. Mechanical stair pressurization is the most commonly used approach to meet this requirement for high rise buildings in the U.S.
- Pressurized elevator hoistways — The IBC permits the omission of elevator lobbies if a hoistway pressurization system is provided. In order to meet the aesthetic and functional needs of the building, this design option is often chosen.
- Post-fire smoke removal — Post-fire smoke removal systems are intended to facilitate smoke removal during post-fire salvage and overhaul operations. To meet this requirement, the current IBC and various previous codes have allowed operable windows/panels, or mechanical equipment capable of providing a prescribed number of air changes per hour.
- Zoned smoke control system — The building is divided into separate smoke control zones and mechanical equipment creates pressure differentials to inhibit smoke spread. Mechanical exhaust is provided for the areas containing smoke and pressurization is provided for the other contiguous zones. In a high rise building, zones may consist of entire floors, but sometimes floors are subdivided into multiple zones